Compose schema

Generated from compose.v1.schema.json. A compose spec describes a whole video (a body, what is drawn over it and what plays under it) and compiles to a project document. The model types it embeds are the same as in the project schema.

ComposeSpec

A whole video: a body, what is drawn over it, and what plays under it.

Field	Type	Description
audio	Node[]	Sound beside the body's: audio and music_bed nodes, placed as overlays are.
bodyrequired	Node	The main picture, from time zero. Its length is the video's unless duration says otherwise.
canvas	Canvas	Size, rate and background. Default youtube-1080p. Default: "youtube-1080p"
compose_version	1	Spec version. This build reads only COMPOSE_VERSION. Default: 1
duration	number | null	The video's length in seconds. Default: the body's.
loudness	Loudness | null	The loudness an export normalizes the mix to. The project does not hold it: it comes back as an export option.
name	string | null	The project's name. Default video.
overlays	Node[]	Nodes drawn over the body, each over the ones before, placed by their own at (default 0) and lasting to the end unless they say otherwise.
theme	ThemeChoice	Fonts, colors, sizes and default timings. Default clean-dark. Default: "clean-dark"

Align

A point of an area: its center, an edge's middle or a corner.

• "center" The center.
• "top" The top edge's middle.
• "bottom" The bottom edge's middle.
• "left" The left edge's middle.
• "right" The right edge's middle.
• "top-left" The top-left corner.
• "top-right" The top-right corner.
• "bottom-left" The bottom-left corner.
• "bottom-right" The bottom-right corner.

AlignContent

Where the lines of a wrapping flex container, or a grid's rows, lie across the container.

• "start" Packed at the start.
• "center" Packed in the middle.
• "end" Packed at the end.
• "space_between" The first at the start, the last at the end, equal space between.
• "space_around" Equal space around each.
• "space_evenly" Equal space between each and at both ends.
• "stretch" Grown to fill the container.

AlignItems

Where children lie across a flex container's main axis, or in their grid areas.

• "start" At the start.
• "center" In the middle.
• "end" At the end.
• "stretch" Across the whole line or area.

AnimatedPoint

A position that can move along curves between its keyframes.

Its JSON is that of an Animated<Vec2>, plus optional spatial tangents on each keyframe: with them, the value travels along the cubic Bezier from one keyframe's value through its out_tangent and the next keyframe's in_tangent, at the speed its timing curve sets along the curve's length. Without them it moves in a straight line, as an Animated<Vec2> does.

One of:

mode: "constant"

A value without animation.

Field	Type	Description
valuerequired	Vec2	Value used at every timestamp.

mode: "keyframes"

Values evaluated from their keyframe sequence.

Field	Type	Description
keyframesrequired	PointKeyframe[]	Strictly ascending keyframes. The evaluator clamps outside the sequence.

Animated_EffectValue

A value that is either constant or controlled by sorted keyframes.

One of:

mode: "constant"

A value without animation.

Field	Type	Description
valuerequired	EffectValue	Value used at every timestamp.

mode: "keyframes"

Values evaluated from their keyframe sequence.

Field	Type	Description
keyframesrequired	Keyframe_EffectValue[]	Strictly ascending keyframes. The evaluator clamps outside the sequence.

Animated_Insets

A value that is either constant or controlled by sorted keyframes.

One of:

mode: "constant"

A value without animation.

Field	Type	Description
valuerequired	Insets	Value used at every timestamp.

mode: "keyframes"

Values evaluated from their keyframe sequence.

Field	Type	Description
keyframesrequired	Keyframe_Insets[]	Strictly ascending keyframes. The evaluator clamps outside the sequence.

Animated_LayoutLength

A value that is either constant or controlled by sorted keyframes.

One of:

mode: "constant"

A value without animation.

Field	Type	Description
valuerequired	LayoutLength	Value used at every timestamp.

mode: "keyframes"

Values evaluated from their keyframe sequence.

Field	Type	Description
keyframesrequired	Keyframe_LayoutLength[]	Strictly ascending keyframes. The evaluator clamps outside the sequence.

Animated_LayoutOffset

A value that is either constant or controlled by sorted keyframes.

One of:

mode: "constant"

A value without animation.

Field	Type	Description
valuerequired	LayoutOffset	Value used at every timestamp.

mode: "keyframes"

Values evaluated from their keyframe sequence.

Field	Type	Description
keyframesrequired	Keyframe_LayoutOffset[]	Strictly ascending keyframes. The evaluator clamps outside the sequence.

Animated_LayoutSize

A value that is either constant or controlled by sorted keyframes.

One of:

mode: "constant"

A value without animation.

Field	Type	Description
valuerequired	LayoutSize	Value used at every timestamp.

mode: "keyframes"

Values evaluated from their keyframe sequence.

Field	Type	Description
keyframesrequired	Keyframe_LayoutSize[]	Strictly ascending keyframes. The evaluator clamps outside the sequence.

Animated_Paint

A value that is either constant or controlled by sorted keyframes.

One of:

mode: "constant"

A value without animation.

Field	Type	Description
valuerequired	Paint	Value used at every timestamp.

mode: "keyframes"

Values evaluated from their keyframe sequence.

Field	Type	Description
keyframesrequired	Keyframe_Paint[]	Strictly ascending keyframes. The evaluator clamps outside the sequence.

Animated_Path

A value that is either constant or controlled by sorted keyframes.

One of:

mode: "constant"

A value without animation.

Field	Type	Description
valuerequired	Path	Value used at every timestamp.

mode: "keyframes"

Values evaluated from their keyframe sequence.

Field	Type	Description
keyframesrequired	Keyframe_Path[]	Strictly ascending keyframes. The evaluator clamps outside the sequence.

Animated_Vec2

A value that is either constant or controlled by sorted keyframes.

One of:

mode: "constant"

A value without animation.

Field	Type	Description
valuerequired	Vec2	Value used at every timestamp.

mode: "keyframes"

Values evaluated from their keyframe sequence.

Field	Type	Description
keyframesrequired	Keyframe_Vec2[]	Strictly ascending keyframes. The evaluator clamps outside the sequence.

Animated_float

A value that is either constant or controlled by sorted keyframes.

One of:

mode: "constant"

A value without animation.

Field	Type	Description
valuerequired	number (float)	Value used at every timestamp.

mode: "keyframes"

Values evaluated from their keyframe sequence.

Field	Type	Description
keyframesrequired	Keyframe_float[]	Strictly ascending keyframes. The evaluator clamps outside the sequence.

Animated_string

A value that is either constant or controlled by sorted keyframes.

One of:

mode: "constant"

A value without animation.

Field	Type	Description
valuerequired	string	Value used at every timestamp.

mode: "keyframes"

Values evaluated from their keyframe sequence.

Field	Type	Description
keyframesrequired	Keyframe_string[]	Strictly ascending keyframes. The evaluator clamps outside the sequence.

AudioEffect

A serializable single-input audio effect applied to a clip or track bus.

Sidechain ducking is not an entry here because it consumes a second input. It is authored per track through Ducking.

One of:

type: "eq"

Cascaded biquad sections.

Field	Type	Description
bandsrequired	EqBand[]	Ordered filter sections, 1 to MAX_EQ_BANDS of them.

type: "compressor"

Lookahead dynamic range compression.

Field	Type	Description
attack_msrequired	number (float)	Attack time in milliseconds, positive and at most MAX_ENVELOPE_MS.
lookahead_ms	number (float)	Lookahead in milliseconds, at most MAX_LOOKAHEAD_MS. Reported as graph latency. Default: 0
ratiorequired	number (float)	Downward ratio, from one (unity) to MAX_COMPRESSOR_RATIO.
release_msrequired	number (float)	Release time in milliseconds, positive and at most MAX_ENVELOPE_MS.
threshold_dbrequired	number (float)	Level above which gain reduction begins, in decibels from MIN_LEVEL_DB to 0.

type: "reverb"

Schroeder reverberation.

Field	Type	Description
dampingrequired	number (float)	High-frequency damping, in 0..=1.
mixrequired	number (float)	Wet mix, in 0..=1.
room_sizerequired	number (float)	Room size, in 0..=1.

AudioProperties

Per-clip audio presentation controls.

Field	Type	Description
effects	AudioEffect[]	Ordered single-input effects applied before the track bus, at most MAX_CHAIN_EFFECTS. Default: []
fade_in	MediaTime	Fade-in duration measured from the clip's timeline start. Non-negative. Default: 0
fade_out	MediaTime	Fade-out duration measured back from the clip's timeline end. Non-negative. Default: 0
fade_shape	FadeShape	Curve used by both fades. Default: "linear"
gain	Animated_float	Animated linear amplitude constrained to 0..=MAX_GAIN. Default: {"mode":"constant","value":1}
muted	boolean	Silences this clip without removing it. Default: false
pan	Animated_float	Animated stereo position from -1 (left) to 1 (right). Default: {"mode":"constant","value":0}

AudioStreamShape

An audio stream's channel count and sample rate.

Field	Type	Description
channelsrequired	integer (uint32)	Channel count.
sample_raterequired	integer (uint32)	Samples per second per channel.

CacheIntent

Whether a runtime may keep and reuse a clip's rendered picture.

• "auto" The runtime decides, keeping pictures whose inputs it can identify.
• "pin" Keep it ahead of other pictures, and bake its range when a host bakes render caches.
• "bypass" Always render it live: nothing it draws is read from or kept in a cache.

Canvas

The canvas: a preset name, or its parts.

One of:

string

A preset: youtube-1080p (1920x1080), youtube-4k (3840x2160), youtube-720p (1280x720), shorts (1080x1920), square (1080x1080), or portrait (1080x1350); all at 30 fps.

<a href="#customcanvas">CustomCanvas</a>

A preset with some parts replaced, or every part given.

CaptionCue

Text shown over one timeline interval.

Field	Type	Description
textrequired	string	The text; \n starts a line. Non-empty, at most MAX_TEXT_CONTENT_BYTES bytes.
timeline_rangerequired	TimeRange	When the cue shows. Non-empty and not before zero.

CaptionStyle

How captions look.

• "outline" Text with a dark band around the glyphs, near the bottom.
• "boxed" Text on a panel behind each line, near the bottom.
• "bar-bottom" Text centered on a translucent bar across the canvas, near the bottom, the bar shown as long as the captions.
• "bold-center" Larger outlined text a little below the middle, as short-form video draws it.

Captions

What a caption track shows: its cues, in one style.

Field	Type	Description
cuesrequired	CaptionCue[]	Cues in timeline order, none overlapping another: a track shows one cue at a time. Simultaneous captions take one track each.
style	TextStyle	How every cue of the track looks. Default: {"align":"center","anchor":{"x":0.5,"y":1},"background":n…

CaptionsNode

Timed text.

Field	Type	Description
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
color	Rgba | null	Text color. Default: the theme's.
cues	Cue[]	Cues as given, in seconds from the node's start.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
file	string | null	A SubRip (.srt) or WebVTT (.vtt) file, read by the binding.
font_size	number | null	Font size in pixels. Default: the theme's caption size.
id	string | null	The node's name, for other nodes to refer to.
max_chars	integer | null	The longest cue words are grouped into, in characters. Default 32 on a tall canvas, 42 on a wide one.
position	number | null	Where the text's middle lies, as a fraction of the canvas height. Default: the style's, which depends on the canvas's shape.
srt	string | null	SubRip text.
style	CaptionStyle	How the captions look. Default outline. Default: "outline"
vtt	string | null	WebVTT text.
words	Cue[]	Words with their times, as speech recognition gives them; they are grouped into cues of up to max_chars characters.

Clip

A reference to a source over independent timeline and source ranges.

Field	Type	Description
audio	AudioProperties	Presentation controls applied to this clip's audio. Default: {"effects":[],"fade_in":0,"fade_out":0,"fade_shape":"line…
blend_mode	ClipBlendMode	Artistic operation used when this clip is composited over earlier layers. Default: "normal"
cache	CacheIntent	Whether a runtime may keep and reuse the clip's rendered picture. Never changes what renders: a kept picture is the one a live render draws.
composition	ClipComposition | null	The composition graph that builds the clip's picture from its source, with the clip's time mapping onto it. Without one the clip shows its source as it is. Visual clips only. Default: null
idrequired	ClipId	Stable clip identity.
masks	ShapeMask[]	Shapes that limit where the clip is visible, applied in order after its composition and before its transform. At most MAX_CLIP_MASKS; visual clips only. Default: []
matte	Matte | null	Another visual clip whose picture sets where this clip is visible. Default: null
source_idrequired	SourceId	Source consumed by this clip.
source_rangerequired	TimeRange	Interval read from the source timeline.
time_map	TimeMap	How timeline time maps onto the source range. Default: {"type":"forward"}
timeline_rangerequired	TimeRange	Destination interval on the project timeline.
visual	VisualProperties	Resolution-independent visual presentation controls. Default: {"anchor":{"x":0.5,"y":0.5},"opacity":{"mode":"constant",…

ClipBlendMode

Artistic blend operation stored independently from a renderer implementation.

The modes are those of W3C Compositing and Blending Level 1 (the CSS mix-blend-mode values), with the specification's formulas.

• "normal" Preserve source color and apply source-over coverage.
• "multiply" Multiply source and backdrop components.
• "screen" Inverse-multiply source and backdrop components.
• "overlay" Multiply dark backdrop regions and screen light regions.
• "darken" The darker of source and backdrop, per channel.
• "lighten" The lighter of source and backdrop, per channel.
• "color_dodge" Brighten the backdrop to reflect the source.
• "color_burn" Darken the backdrop to reflect the source.
• "hard_light" Multiply or screen, depending on the source.
• "soft_light" Darken or lighten, depending on the source: a diffused hard light.
• "difference" The absolute difference of source and backdrop.
• "exclusion" Like difference, with lower contrast.
• "hue" The source's hue with the backdrop's saturation and luminosity.
• "saturation" The source's saturation with the backdrop's hue and luminosity.
• "color" The source's hue and saturation with the backdrop's luminosity.
• "luminosity" The source's luminosity with the backdrop's hue and saturation.

ClipComposition

A clip's use of a Composition, and how its time maps onto it.

Composition time is offset + (t - clip start) * scale for timeline time t, rounded down to a tick. Moving a clip keeps its offset, so its animation moves with it; trimming its start by d adds d * scale to the offset, so what remains of the animation stays where it was. Extending the start before composition time zero makes the offset negative: settings hold their first keyframe there, and media nodes show their first frame.

Field	Type	Description
idrequired	CompositionId	The composition shown.
offset	MediaTime	Composition time at the clip's start. Default: 0
scale	TimeScale	Composition time per timeline time. Default: {"den":1,"num":1}

ClipEffect

One versioned runtime effect invocation: a composition's effect or transition node, or a timeline transition.

Field	Type	Description
idrequired	string	Stable effect definition identifier.
params	{ [name]: Animated_EffectValue }	Named parameter values, constant or keyframed. Omitted entries use definition defaults. Keyframe times are composition times in a composition node and timeline times in a timeline transition. A parameter's keyframes all have one value type, and enum and bool keyframes only hold. An interpolated value that a timing curve carries past the parameter's range is clamped to it; an authored value outside it is an error. Default: {}
resources	{ [name]: EffectResourceId }	Named external resources matched against the effect definition. Default: {}
versionrequired	integer (uint32)	Exact effect definition version required by the project.

ClipId

A stable timeline-clip identifier.

Type: string

ClipTransition

A two-input transition over the overlap of two visual clips.

Field	Type	Description
easingrequired	Easing	Timing curve applied to the transition's linear progress. The eased progress is clamped to 0..=1, the domain transition shaders define.
effectrequired	ClipEffect	Versioned transition shader and named parameter values.
from_cliprequired	ClipId	Clip sampled as transition progress zero.
timeline_rangerequired	TimeRange	Half-open timeline interval over which both clips must be active.
to_cliprequired	ClipId	Clip sampled as transition progress one.

ColorMatrix

Coefficients used to decode source components.

• "bt601" SD BT.601 YUV coefficients.
• "bt709" HD BT.709 YUV coefficients.
• "bt2020_ncl" BT.2020 non-constant-luminance YUV coefficients.
• "rgb" Source components are already RGB.

ColorMetadata

Host-independent video color description.

Field	Type	Description
dynamic_rangerequired	DynamicRange	SDR or HDR signal classification: HDR exactly when transfer is PQ or HLG (is_consistent).
matrixrequired	ColorMatrix	YUV-to-RGB coefficient family, or RGB for already converted sources.
primariesrequired	ColorPrimaries	RGB chromaticity standard.
rangerequired	ColorRange	Encoded component range.
transferrequired	TransferFunction	Nonlinear transfer curve.

ColorPrimaries

RGB primary chromaticities a source or export declares.

• "bt601" SD video primaries.
• "bt709" HD video and sRGB primaries.
• "bt2020" Wide-gamut BT.2020 primaries, normally indicating HDR input.

ColorRange

Nominal encoded component range.

• "limited" Studio/video range.
• "full" Full component range.

Composition

An acyclic graph of image operations with one selected output.

Field	Type	Description
controls	CompositionControl[]	The node settings a group node may set, by name.
idrequired	CompositionId	Stable composition identity.
inputs	string[]	The images a group node gives it, by name, in port order: its GroupInput nodes read them.
nodes	CompositionNode[]	The graph's nodes. Their order has no meaning: a node may name a node listed after it as its input. Default: []
output	NodeId | null	The node whose image is the composition's picture. A composition without one saves, but cannot be rendered. Default: null

CompositionControl

A node setting a composition exposes to the group nodes that use it: an effect or transition parameter of one of its nodes.

Field	Type	Description
namerequired	string	The name a group node sets it by; unique in the composition.
noderequired	NodeId	The effect or transition node.
paramrequired	string	The parameter of its effect.

CompositionId

A stable composition-graph identifier.

Type: string

CompositionNode

One image operation in a Composition.

Field	Type	Description
bypass	boolean	Whether the node passes its bypass_input through unchanged instead of operating. A node without inputs cannot be bypassed. Default: false
idrequired	NodeId	Identity, unique within its composition.
oprequired	NodeOp	What the node does, with its inputs and settings.

Cue

Text over an interval.

Field	Type	Description
endrequired	number (double)	End in seconds.
startrequired	number (double)	Start in seconds.
textrequired	string	The text.

CustomCanvas

A canvas by its parts.

Field	Type	Description
background	Rgba | null	The opaque color under everything. Default: the theme's.
frame_rate	FrameRateChoice | null	Frames per second: an integer, 23.976, 29.97 or 59.94, or the project's exact {num, den}.
height	integer | null	Height in pixels.
preset	string | null	The preset the other parts replace parts of. Default youtube-1080p.
width	integer | null	Width in pixels.

Dash

A dash pattern.

Field	Type	Description
offset	Animated_float	How far into the pattern the stroke starts. Default: {"mode":"constant","value":0}
patternrequired	Animated_float[]	Alternating dash and gap lengths, as fractions of the shorter side: one to MAX_DASH_ENTRIES non-negative entries, not all zero. An odd count repeats once more to pair up.

Display

How a box lays its children out.

• "flex" CSS flexbox.
• "grid" CSS grid.

Ducking

Sidechain ducking authored on the track that is attenuated.

Field	Type	Description
attack_msrequired	number (float)	Attack time in milliseconds, positive and at most MAX_ENVELOPE_MS.
depth_dbrequired	number (float)	Maximum attenuation in decibels, from MIN_LEVEL_DB to 0.
release_msrequired	number (float)	Release time in milliseconds, positive and at most MAX_ENVELOPE_MS.
sidechain_trackrequired	TrackId	Track whose mixed output drives the envelope follower.
thresholdrequired	number (float)	Linear level above which attenuation begins. Positive.

DynamicRange

Whether a signal is standard or high dynamic range. It follows the transfer: hdr exactly when the transfer is PQ or HLG, and a color whose two fields disagree is refused.

• "sdr" Standard dynamic range: a BT.709 or sRGB transfer.
• "hdr" High dynamic range: a PQ or HLG transfer, which a project tone-maps into the SDR working space or refuses, as its color pipeline says.

Easing

A timing curve from linear progress to eased progress, without a hold.

Transitions use it directly; keyframe Interpolation adds hold.

One of:

type: "linear"

Progress advances at a constant rate.

type: "cubic_bezier"

Progress follows a CSS cubic-bezier() curve.

Field	Type	Description
x1required	number (float)	Horizontal coordinate of the first control point, in 0..=1.
x2required	number (float)	Horizontal coordinate of the second control point, in 0..=1.
y1required	number (float)	Vertical coordinate of the first control point.
y2required	number (float)	Vertical coordinate of the second control point.

EffectResourceId

A stable effect-resource identifier.

Type: string

EffectValue

Serializable value supplied to one runtime effect parameter.

One of:

type: "float"

One finite scalar.

Field	Type	Description
valuerequired	number (float)

type: "vec2"

Two finite components, normally in normalized coordinates.

Field	Type	Description
valuerequired	number (float)[]

type: "vec4"

Four finite components that are not a color, such as per-channel thresholds; they keyframe component by component.

Field	Type	Description
valuerequired	number (float)[]

type: "color"

Straight (not premultiplied), sRGB-encoded RGBA components in the inclusive unit interval, as a color picker shows them.

Field	Type	Description
valuerequired	number (float)[]

type: "enum"

Index into an effect definition's enum choices.

Field	Type	Description
valuerequired	integer (uint32)

type: "bool"

Boolean toggle.

Field	Type	Description
valuerequired	boolean

EqBand

A single equalizer section stored independently from its DSP implementation.

Field	Type	Description
frequency_hzrequired	number (float)	Center or corner frequency in hertz, within EQ_FREQUENCY_RANGE_HZ.
gain_db	number (float)	Peaking gain in decibels, at most MAX_EQ_GAIN_DB either way. Ignored by the pass filters. Default: 0
kindrequired	EqBandKind	Filter shape.
qrequired	number (float)	Resonance, within EQ_Q_RANGE. Larger values produce narrower bands.

EqBandKind

The filter shape of one equalizer band.

• "peaking" Bell-shaped parametric band.
• "low_pass" Second-order low-pass.
• "high_pass" Second-order high-pass.

FadeShape

Curve applied by a clip's fade in and fade out.

• "linear" Amplitude moves linearly. Two linear fades over one overlap dip by 6 dB.
• "equal_power" Amplitude follows a quarter sine. Two of these crossfade at constant power, which is what overlapping clips normally want.

FileKind

What a media file holds, when its extension does not say.

• "video" Moving pictures, perhaps with sound.
• "image" A still picture.
• "audio" Sound alone.

FillRule

Which regions of a path are inside it.

• "nonzero" Where the outline winds around a point at all.
• "evenodd" Where it winds around a point an odd number of times.

Fit

How a picture fills its area.

• "contain" All of it, as large as fits; the rest of the area stays empty.
• "cover" All of the area, cropped to it.
• "fill" Stretched to the area.
• "none" At its own size in pixels, cropped to the area.

FlexDirection

The main axis of a flex container.

• "row" Left to right.
• "column" Top to bottom.
• "row_reverse" Right to left.
• "column_reverse" Bottom to top.

FlexWrap

Whether a flex container's children wrap.

• "nowrap" One line.
• "wrap" As many lines as the children need.

FrameRate

A positive rational frame rate in reduced form, at most one frame per tick (120 000 frames per second).

Field	Type	Description
denrequired	integer (uint32)	Seconds per num frames. Positive.
numrequired	integer (uint32)	Frames per den seconds. Positive, and at most 120 000 times den.

FrameRateChoice

A frame rate, as a number or exactly.

One of:

number <span class="a2-muted">(double)</span>

Frames per second: an integer, or 23.976, 29.97 or 59.94 for the NTSC rates.

<a href="#framerate">FrameRate</a>

The project's exact rate.

Generator

The picture of a generated source.

A generated picture has the canvas's size and aspect, like a source that fills the frame at scale 1. Positions are in its normalized space, (0, 0) top-left to (1, 1) bottom-right; lengths (radii, stroke widths) are fractions of its shorter side, so the picture is the same at any render resolution. A fill or text does not change over time (a clip animates it with its transform, effects, and masks); shapes and layouts may.

One of:

type: "fill"

Paint over the whole picture.

Field	Type	Description
paintrequired	Paint	What covers the picture.

type: "shapes"

Shapes drawn from an ordered content tree, as an After Effects shape layer or a Lottie shape layer draws them. Unlike the other generators, its picture changes over time: every value in the tree may be keyframed, in the picture's time.

Field	Type	Description
itemsrequired	ShapeItem[]	The content tree, front first. See ShapeItem.

type: "text"

Text on a transparent picture, laid out and placed by its style as a caption track's cues are: its size and wrapping width fractions of the canvas, its anchor at style.position. The engine draws it with the fonts its host registered.

Field	Type	Description
style	TextStyle	How it looks and where it lies. The font size is at most MAX_TEXT_GENERATOR_FONT_SIZE. Default: {"align":"center","anchor":{"x":0.5,"y":1},"background":n…
textrequired	string	The text; \n starts a line. Non-empty, at most MAX_TEXT_CONTENT_BYTES bytes.

type: "layout"

Boxes laid out by CSS flexbox around their text and shapes. Its picture changes over time when any value in the tree is keyframed, in the picture's time. The engine lays it out with the fonts it draws with. See LayoutNode.

Field	Type	Description
rootrequired	LayoutNode	The root box: the whole picture.

GradientStop

One color of a gradient.

Field	Type	Description
colorrequired	Rgba	Color at that position.
offsetrequired	number (float)	Position along the gradient, in 0..=1, not before the previous stop.

GridAutoFlow

How a grid places items that have no placement of their own.

• "row" Filling each row, adding rows.
• "column" Filling each column, adding columns.
• "row_dense" As row, filling earlier holes.
• "column_dense" As column, filling earlier holes.

GridLength

How long a grid of clips of different lengths lasts.

• "shortest" As long as its shortest cell.
• "longest_freeze" As long as its longest; shorter clips hold their last frame.
• "longest_loop" As long as its longest; shorter clips play again from their start.

GridPlacement

Where a grid item lies on one axis, as CSS writes it: 2, "1 / 3", "span 2", "2 / span 3", "auto". Lines count from 1, or from -1 at the end.

One of:

integer

string

Inset

Space kept clear inside an area.

One of:

number <span class="a2-muted">(float)</span>

The same on every side.

number <span class="a2-muted">(float)</span>[]

[top, right, bottom, left].

Insets

A length on each side of a box: one length for every side, the CSS shorthand of one to four lengths ("8px 16px": top first, clockwise), or the sides object, missing sides 0.

One of:

number <span class="a2-muted">(float)</span>

string

object

Field	Type	Description
bottom	LayoutSize
left	LayoutSize
right	LayoutSize
top	LayoutSize

Interpolation

Interpolation from one keyframe to the next.

Values are interpolated numerically: a rotation from 0 to 720 degrees turns twice, and one from 0 to 360 turns once. A host that wants the shortest path normalizes its keyframe values.

One of:

type: "hold"

Keep this keyframe's value until the next keyframe.

type: "linear"

Move to the next value at a constant rate.

type: "cubic_bezier"

Move to the next value along a CSS cubic-bezier() timing curve.

Field	Type	Description
x1required	number (float)	Horizontal coordinate of the first control point, in 0..=1.
x2required	number (float)	Horizontal coordinate of the second control point, in 0..=1.
y1required	number (float)	Vertical coordinate of the first control point.
y2required	number (float)	Vertical coordinate of the second control point.

JustifyContent

Where children lie along a container's main axis, or a grid's columns in it.

• "start" Packed at the start.
• "center" Packed in the middle.
• "end" Packed at the end.
• "space_between" The first at the start, the last at the end, equal space between.
• "space_around" Equal space around each.
• "space_evenly" Equal space between each and at both ends.

Keyframe_EffectValue

One timestamped control value.

Field	Type	Description
interpolationrequired	Interpolation	Interpolation from this keyframe to its successor.
timerequired	MediaTime	Timestamp of this value: timeline time, except in a composition node's settings, which are keyed in composition time, and in a shapes or layout generator's tree, which is keyed in its picture's time.
valuerequired	EffectValue	Value at time.

Keyframe_Insets

One timestamped control value.

Field	Type	Description
interpolationrequired	Interpolation	Interpolation from this keyframe to its successor.
timerequired	MediaTime	Timestamp of this value: timeline time, except in a composition node's settings, which are keyed in composition time, and in a shapes or layout generator's tree, which is keyed in its picture's time.
valuerequired	Insets	Value at time.

Keyframe_LayoutLength

One timestamped control value.

Field	Type	Description
interpolationrequired	Interpolation	Interpolation from this keyframe to its successor.
timerequired	MediaTime	Timestamp of this value: timeline time, except in a composition node's settings, which are keyed in composition time, and in a shapes or layout generator's tree, which is keyed in its picture's time.
valuerequired	LayoutLength	Value at time.

Keyframe_LayoutOffset

One timestamped control value.

Field	Type	Description
interpolationrequired	Interpolation	Interpolation from this keyframe to its successor.
timerequired	MediaTime	Timestamp of this value: timeline time, except in a composition node's settings, which are keyed in composition time, and in a shapes or layout generator's tree, which is keyed in its picture's time.
valuerequired	LayoutOffset	Value at time.

Keyframe_LayoutSize

One timestamped control value.

Field	Type	Description
interpolationrequired	Interpolation	Interpolation from this keyframe to its successor.
timerequired	MediaTime	Timestamp of this value: timeline time, except in a composition node's settings, which are keyed in composition time, and in a shapes or layout generator's tree, which is keyed in its picture's time.
valuerequired	LayoutSize	Value at time.

Keyframe_Paint

One timestamped control value.

Field	Type	Description
interpolationrequired	Interpolation	Interpolation from this keyframe to its successor.
timerequired	MediaTime	Timestamp of this value: timeline time, except in a composition node's settings, which are keyed in composition time, and in a shapes or layout generator's tree, which is keyed in its picture's time.
valuerequired	Paint	Value at time.

Keyframe_Path

One timestamped control value.

Field	Type	Description
interpolationrequired	Interpolation	Interpolation from this keyframe to its successor.
timerequired	MediaTime	Timestamp of this value: timeline time, except in a composition node's settings, which are keyed in composition time, and in a shapes or layout generator's tree, which is keyed in its picture's time.
valuerequired	Path	Value at time.

Keyframe_Vec2

One timestamped control value.

Field	Type	Description
interpolationrequired	Interpolation	Interpolation from this keyframe to its successor.
timerequired	MediaTime	Timestamp of this value: timeline time, except in a composition node's settings, which are keyed in composition time, and in a shapes or layout generator's tree, which is keyed in its picture's time.
valuerequired	Vec2	Value at time.

Keyframe_float

One timestamped control value.

Field	Type	Description
interpolationrequired	Interpolation	Interpolation from this keyframe to its successor.
timerequired	MediaTime	Timestamp of this value: timeline time, except in a composition node's settings, which are keyed in composition time, and in a shapes or layout generator's tree, which is keyed in its picture's time.
valuerequired	number (float)	Value at time.

Keyframe_string

One timestamped control value.

Field	Type	Description
interpolationrequired	Interpolation	Interpolation from this keyframe to its successor.
timerequired	MediaTime	Timestamp of this value: timeline time, except in a composition node's settings, which are keyed in composition time, and in a shapes or layout generator's tree, which is keyed in its picture's time.
valuerequired	string	Value at time.

LayoutBorder

A border inside the border box, as wide on every side.

Field	Type	Description
paintrequired	Animated_Paint	What covers the border. Positions are normalized to the border box.
widthrequired	Animated_LayoutSize	Width. At least 0.

LayoutInset

Where an absolute box lies in its parent's padding box. A missing side is auto: with neither left nor right, the box keeps its place in the flow on that axis.

Field	Type	Description
bottom	Animated_LayoutLength | null	Distance from the parent's bottom padding edge.
left	Animated_LayoutLength | null	Distance from the parent's left padding edge.
right	Animated_LayoutLength | null	Distance from the parent's right padding edge.
top	Animated_LayoutLength | null	Distance from the parent's top padding edge.

LayoutLength

A length: a number is a fraction of the layout picture's shorter side, "<n>px" pixels of the project canvas, "<n>%" a percent of the parent's content box along the field's axis.

One of:

number <span class="a2-muted">(float)</span>

string

LayoutNode

One box of a layout tree.

A box lays its children out by flexbox (display: flex, the default) or grid (display: grid). It is a container when it has children, a leaf when it has text or shape content, and empty otherwise (a spacer or a decoration). Per box, its background is drawn first, then its border, then its content. Boxes are drawn in document order; a reversed direction or a grid placement moves them, not their order.

Field	Type	Description
align_content	AlignContent | null	Where lines of a wrapping flex container, or a grid's rows, lie across the container. Default stretch.
align_items	AlignItems | null	Where children lie across the main axis, or in their grid areas' rows. Default stretch.
align_self	AlignItems | null	Where the box lies across its flex container's main axis, or in its grid area's row. None follows the parent's align_items.
aspect_ratio	number | null	Width over height. Positive.
background	Animated_Paint | null	What covers the border box, rounded by border_radius. Positions are normalized to the border box.
border	LayoutBorder | null	A border inside the border box.
border_radius	Animated_LayoutSize | null	The corner radius of the border box. At least 0; default 0. A radius past half the box's shorter side is capped.
children	LayoutNode[]	Boxes laid out in this one, in document (and paint) order. Not with text or shape.
color	Rgba | null	Text color. Inherited; the root's is white.
column_gap	Animated_LayoutSize | null	Space between columns, in place of gap. At least 0.
display	Display | null	How the box lays its children out. Default flex. Not on a box with text or shape content, as every container field.
flex_basis	Animated_LayoutLength | null	The main size before growing and shrinking. None is auto.
flex_direction	FlexDirection | null	The main axis of a flex container's children. Default row.
flex_grow	Animated_float | null	How much of a flex container's free space the box takes. At least 0; default 0. Not in a grid, as every flex item field.
flex_shrink	Animated_float | null	How much the box gives up when a flex container's space runs short. At least 0; default 1.
flex_wrap	FlexWrap | null	Whether a flex container's children wrap onto more lines. Default nowrap.
font_family	string | null	The family the box's text draws in, as a text style's font_family. Inherited; the root's is the host's first font.
font_size	Animated_LayoutSize | null	Font size: positive, at most MAX_LAYOUT_FONT_SIZE of the picture's shorter side. Inherited; the root's is 0.05.
font_weight	integer | null	The weight, in [1, 1000], the family's faces are matched by, as CSS Fonts 4 matches font-weight; a variable face draws at it. Not animated. Inherited; the root's is 400.
gap	Animated_LayoutSize | null	Space between children, on both axes. At least 0; default 0.
grid_auto_columns	TrackList | null	The size of a grid's implicit columns. Default auto.
grid_auto_flow	GridAutoFlow | null	How a grid places items without a placement. Default row.
grid_auto_rows	TrackList | null	The size of a grid's implicit rows. Default auto.
grid_column	GridPlacement | null	The box's columns in its grid, as CSS writes them (2, "1 / 3", "span 2"). Default auto.
grid_row	GridPlacement | null	The box's rows in its grid. Default auto.
grid_template_columns	TrackList | null	A grid's explicit columns, as CSS writes them ("1fr 2fr", "repeat(3, minmax(100px, 1fr))"). Default none.
grid_template_rows	TrackList | null	A grid's explicit rows. Default none.
height	Animated_LayoutLength | null	Border-box height. None is auto.
inset	LayoutInset | null	Where an absolute box lies in its parent's padding box.
justify_content	JustifyContent | null	Where children lie along the main (inline, for a grid) axis. Default start.
justify_items	AlignItems | null	Where a grid's children lie in their grid areas' columns. Default stretch.
justify_self	AlignItems | null	Where the box lies in its grid area's column. None follows the parent's justify_items. Not in a flex container, as every grid item field.
letter_spacing	number | null	Space after each character, as a fraction of the font size, in [-0.5, 1], as CSS letter-spacing adds it: none after a line's last character, and none after a character of a cursive script. Not animated. Inherited; the root's is 0.
line_height	number | null	Baseline-to-baseline distance in font sizes, in [0.5, 3]. Each line's em box, 0.8 of a font size above its baseline and 0.2 below, is centred in its line when the line is taller than an em. Inherited; the root's is 1.2.
margin	Animated_Insets | null	Space outside the border, written as padding is. Sides may be negative; there is no auto.
max_height	Animated_LayoutLength | null	Largest height. None is none.
max_width	Animated_LayoutLength | null	Largest width. None is none.
min_height	Animated_LayoutLength | null	Smallest height. None is auto.
min_width	Animated_LayoutLength | null	Smallest width. None is auto, the CSS automatic minimum size.
opacity	Animated_float | null	Opacity of the box and everything in it, as one group, in 0..=1. Drawn after layout; it never moves a box.
outline	TextOutline | null	A band around the glyphs; its width a fraction of the font size. Inherited; the root has none.
overflow	Overflow | null	Whether content past the padding box is drawn. Default visible.
padding	Animated_Insets | null	Space inside the border: a length, the CSS shorthand ("8px 16px"), or the sides object. Sides at least 0; default 0.
position	Position | null	Whether the box is in its parent's flow. Default relative.
rotation_degrees	Animated_float | null	Clockwise rotation of the box and everything in it about its border-box centre, in degrees, after layout.
row_gap	Animated_LayoutSize | null	Space between rows (between lines of a wrapping row flex container), in place of gap. At least 0.
scale	Animated_Vec2 | null	Per-axis scale of the box and everything in it about its border-box centre, after layout.
shape	LayoutShape | null	Shapes drawn on a picture the size of the box's content box. Not with children or text.
text	Animated_string | null	The box's text, wrapped at its content width and drawn in the style it inherits; \n starts a line. At most MAX_TEXT_CONTENT_BYTES bytes per value; may be empty. Its keyframes all hold. Not with children or shape.
text_align	TextAlign | null	How lines align within the content width. Inherited; the root's is start.
translate	Animated_LayoutOffset | null	Offset of the box and everything in it, after layout: the object, or one or two lengths as CSS translate writes them.
width	Animated_LayoutLength | null	Border-box width. None is auto. Not on the root, as every item field.

LayoutOffset

An offset, x right and y down: one or two lengths as CSS translate writes them (y 0 when missing), or {x, y}.

One of:

string

object

Field	Type	Description
xrequired	LayoutSize
yrequired	LayoutSize

LayoutShape

A box's shapes, drawn as a shapes generator draws its items on a picture the size of the box's content box: positions normalized to that box, lengths fractions of its shorter side. A shape box has no size of its own.

Field	Type	Description
itemsrequired	ShapeItem[]	The content tree, front first.

LayoutSize

A length that may not be a percent: a number is a fraction of the layout picture's shorter side, "<n>px" pixels of the project canvas.

One of:

number <span class="a2-muted">(float)</span>

string

LineCap

How an open stroke ends.

• "butt" Flat at the end point.
• "round" A half circle past the end point.
• "square" A half square past the end point.

LineJoin

How stroke segments meet at a vertex.

• "miter" Extended edges meeting at a point, up to the miter limit.
• "round" A circular arc.
• "bevel" A straight cut across the corner.

LinearPrimaries

Named RGB primaries linear-light media may be in, each with its own white point.

• "bt709" ITU-R BT.709 and sRGB, D65 white.
• "bt2020" ITU-R BT.2020, D65 white.
• "p3_d65" DCI-P3 primaries with a D65 white, as Display P3.
• "aces_ap0" ACES AP0 (SMPTE ST 2065-1), the ACES white.
• "aces_ap1" ACES AP1 (ACEScg), the ACES white.

LoopMode

How each pass of a Loop follows the one before.

• "repeat" Every pass plays forward, from the start again. Sound fades out and in over LOOP_FADE_SECONDS at each wrap, so the jump does not click.
• "ping_pong" Passes alternate forward and backward.

Loudness

The loudness an export normalizes to: a target, or a target and a ceiling.

One of:

number <span class="a2-muted">(double)</span>

Integrated loudness in LUFS, under a -1 dBTP ceiling.

<a href="#loudnesstarget">LoudnessTarget</a>

Integrated loudness and a true-peak ceiling.

LoudnessTarget

The loudness an export normalizes to.

Field	Type	Description
target_lufsrequired	number (double)	Integrated loudness, -60..=0 LUFS.
true_peak_ceiling_dbtp	number (double)	True-peak ceiling, -20..=0 dBTP. Default -1. Default: -1

MaskMode

How a mask combines with the coverage of the masks before it.

Coverage starts empty when the first mask adds, and full otherwise, so a clip whose only mask subtracts is visible outside the shape.

• "add" Union: c + m - c * m.
• "subtract" Difference: c * (1 - m).
• "intersect" Intersection: c * m.

Matte

Another visual clip whose picture sets where this clip is visible.

The matte clip is drawn, with its own transform and effects, only into the matte; a clip that is any clip's matte is never composited itself. Where the matte clip is not active, its coverage is zero.

Field	Type	Description
moderequired	MatteMode	What of that picture is the coverage.
sourcerequired	ClipId	The clip whose picture is the matte.

MatteMode

Which property of the matte clip's picture is coverage.

• "alpha" Its alpha.
• "alpha_inverted" One minus its alpha.
• "luma" Its luminance over black: BT.709 weights on linear light, times alpha.
• "luma_inverted" One minus that luminance.

MediaFingerprint

Evidence of a source's media, each part recorded only when it was known.

A matching content hash proves the same bytes. Without one, the other parts can only show a difference. modified_ms narrows a search for candidates and never decides whether a candidate is the same media.

Field	Type	Description
byte_length	integer | null	The file's length in bytes.
color	ColorMetadata | null	The color the decoded pictures carry.
content_sha256	string | null	SHA-256 of the whole file, as 64 lowercase hexadecimal digits.
duration_ticks	integer | null	Where the media ends on its own timeline, in ticks: its first presentation plus its length, the end of any source range that reads it. A transport stream that starts at 1.4 s and lasts 2 s ends at 3.4 s. Non-negative.
modified_ms	integer | null	The file's modification time, in milliseconds since the Unix epoch.
streams	StreamTopology | null	The streams the file carries.

MediaItem

A file given by its path alone, or a media node.

One of:

string

The file, everything else by default.

<a href="#node">Node</a>

A media node.

MediaKind

The payload domain of a source.

• "video" A video stream, potentially with an audio stream.
• "audio" An audio stream.
• "image" A still visual image.
• "generated" A picture the engine draws from the source's Generator. The host supplies nothing for it.
• "composition" A composition of the project, drawn at the source time as its own time. The host supplies nothing for it; the media its nodes read, it supplies as for any composition.

MediaSource

A host-resolved media resource.

Field	Type	Description
color_metadata	ColorMetadata | null	The color a Video source's pictures are in, which wins over what its frames and its stream are tagged with on every host: a host records it at import, or a document declares it to correct missing or wrong tags. None leaves the tags in charge. A still is read as sRGB code values whatever it declares. Default: null
composition	CompositionId | null	The composition a Composition source shows; present exactly for that kind.
fingerprint	MediaFingerprint | null	What the host found at the locator when the project recorded it, so another host can tell whether media it finds is the same. A generated source has none.
generator	Generator | null	What a Generated source draws; present exactly for that kind. Default: null
has_audio	boolean	Whether this source's media has an audio stream: a fact of the file, so every host that imports it records the same, whether or not that host can decode the stream. A host that cannot reports so at run time and plays the source silent; the document keeps the stream for the hosts that can. Audio always does. A Video source declares it so that clips on a visual track contribute to the mix; leaving it unset keeps a video clip silent. Default: false
idrequired	SourceId	Stable source identity.
kindrequired	MediaKind	Media payload domain.
locator	string	Opaque URI or host locator. The engine does not open it directly. Required, except that a Generated or Composition source has none. Default: ""
provider	ProviderSource | null	The extension provider that supplies this source's media, and its settings, when the host's own decoders do not read it.

MediaTime

A signed position or duration in timeline ticks (120 000 per second), at most the largest integer a JavaScript number holds exactly either way.

Type: integer (int64)

MergeLayer

One layer of a Merge.

Field	Type	Description
blend_mode	ClipBlendMode	How the layer blends with the layers under it. Default: "normal"
input	NodeId | null	The layer's image. Default: null
opacity	Animated_float	The layer's opacity, in 0..=1. Default: {"mode":"constant","value":1}

MissingFrames

How an image sequence shows a frame missing from its numbering.

• "reject" A sequence with a missing frame is refused.
• "hold" The frame before it is shown.
• "blank" Nothing is shown: a transparent frame.

Node

One part of a video.

One of:

type: "sequence"

Children one after another, with transitions between them.

Field	Type	Description
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
childrenrequired	Node[]	The children, in play order.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
id	string | null	The node's name, for other nodes to refer to.
transition	TransitionChoice | null	What joins neighbours: a transition overlaps them by its duration. Default none. Only single pictures (media, text, color, layout) can transition into each other.

type: "stack"

Children over each other, each over the ones before.

Field	Type	Description
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
childrenrequired	Node[]	The children, each drawn over the ones before. Each starts at its own at.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
id	string | null	The node's name, for other nodes to refer to.
inset	Inset | null	Pixels kept clear inside the parent's area: one number for every side, or [top, right, bottom, left].

type: "grid"

Children in the cells of a grid, row by row.

Field	Type	Description
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
childrenrequired	Node[]	The cells' contents, row by row.
columns	integer | null	Columns. Default: as square a grid as the children make.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
gap	number (float)	Pixels between cells. Default: 0
id	string | null	The node's name, for other nodes to refer to.
inset	Inset | null	Pixels kept clear inside the parent's area: one number for every side, or [top, right, bottom, left].
length	GridLength	How long the grid lasts when its cells differ, and what a cell that ends early shows. Default shortest. Default: "shortest"

type: "media"

A video or still file.

Field	Type	Description
align	Align | null	Where in its area the picture or text lies. Default center.
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
blur	number | null	A Gaussian blur's radius, as a fraction of the picture's shorter side.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
fade_in	number | null	Seconds of fade in from transparent.
fade_out	number | null	Seconds of fade out to transparent.
fit	Fit | null	How a picture fills its area. Default contain.
id	string | null	The node's name, for other nodes to refer to.
inset	Inset | null	Pixels kept clear inside the parent's area: one number for every side, or [top, right, bottom, left].
kind	FileKind | null	What the file holds. Default: by its extension.
label	string | null	A label a comparison grid shows on the cell.
loop	boolean	Plays a video again from its start while the node lasts.
muted	boolean	Silences a video's sound.
opacity	number | null	Opacity, 0..=1. Default 1.
pathrequired	string	The file. It becomes the source's locator and the export's asset.
speed	number | null	Playback speed of a video: 2 plays it twice as fast. Default 1.
trim_end	number | null	Where in the file a video ends, in seconds. Default: its end.
trim_start	number | null	Where in the file a video starts, in seconds.
volume	number | null	Linear gain of a video's sound. Default 1.
zoom	array | null	A slow zoom over the node's length, [from, to], as multiples of the fitted size.

type: "text"

Text.

Field	Type	Description
align	Align | null	Where in its area the picture or text lies. Default center.
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
background	Rgba | null	A box of this color behind each line.
color	Rgba | null	Color. Default: the theme's text color.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
fade	number | null	Seconds of fade in and out. Default none.
font_family	string | null	Family. Default: the theme's.
font_size	number | null	Font size in pixels. Default: the style's.
id	string | null	The node's name, for other nodes to refer to.
inset	Inset | null	Pixels kept clear inside the parent's area: one number for every side, or [top, right, bottom, left].
max_lines	integer | null	The most lines it may take: with fonts to measure by, a longer text shrinks until it fits. Default: no limit.
opacity	number | null	Opacity, 0..=1. Default 1.
outline	Rgba | null	A band of this color around the glyphs.
style	TextRole	The theme style it starts from. Default body. Default: "body"
textrequired	string	The text; \n starts a line.

type: "color"

An area painted one color.

Field	Type	Description
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
color	Rgba | null	The color. Default: the theme's surface.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
id	string | null	The node's name, for other nodes to refer to.
inset	Inset | null	Pixels kept clear inside the parent's area: one number for every side, or [top, right, bottom, left].

type: "captions"

Timed text from cues, a SubRip or WebVTT file, or word timestamps.

Field	Type	Description
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
color	Rgba | null	Text color. Default: the theme's.
cues	Cue[]	Cues as given, in seconds from the node's start.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
file	string | null	A SubRip (.srt) or WebVTT (.vtt) file, read by the binding.
font_size	number | null	Font size in pixels. Default: the theme's caption size.
id	string | null	The node's name, for other nodes to refer to.
max_chars	integer | null	The longest cue words are grouped into, in characters. Default 32 on a tall canvas, 42 on a wide one.
position	number | null	Where the text's middle lies, as a fraction of the canvas height. Default: the style's, which depends on the canvas's shape.
srt	string | null	SubRip text.
style	CaptionStyle	How the captions look. Default outline. Default: "outline"
vtt	string | null	WebVTT text.
words	Cue[]	Words with their times, as speech recognition gives them; they are grouped into cues of up to max_chars characters.

type: "layout"

A layout generator: boxes, text and shapes laid out by CSS flexbox and grid, as the project writes them.

Field	Type	Description
align	Align | null	Where in its area the picture or text lies. Default center.
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
id	string | null	The node's name, for other nodes to refer to.
inset	Inset | null	Pixels kept clear inside the parent's area: one number for every side, or [top, right, bottom, left].
rootrequired	LayoutNode	The root box, as a project's layout generator writes it.

type: "audio"

A sound file.

Field	Type	Description
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
duck_depth_db	number | null	How far ducking lowers it, in dB (negative). Default -12.
duck_under	string | null	The id of a node (or body) whose sound this ducks under.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
fade_in	number | null	Seconds of fade in.
fade_out	number | null	Seconds of fade out.
id	string | null	The node's name, for other nodes to refer to.
loop	boolean	Plays the file again from its start while the node lasts.
pathrequired	string	The file.
trim_end	number | null	Where in the file it ends, in seconds. Default: its end.
trim_start	number | null	Where in the file it starts, in seconds.
volume	number | null	Linear gain. Default 1.

type: "raw"

Part of a project, as the project writes it: its sources, tracks and compositions, at its own times. Only as an overlay.

Field	Type	Description
assets	{ [name]: string }	Each file a media source of the fragment reads, by source id: the export's assets.
compositions	Composition[]	Compositions its clips show.
sources	MediaSource[]	Sources its tracks read. Their ids must not be the compiler's (s1, s2, ...); a src- prefix keeps them apart.
tracks	Track[]	Tracks drawn over what comes before, at timeline times.

type: "slideshow"

Stills or clips in turn, with transitions and slow zooms.

Field	Type	Description
at	number | null	When it starts in its parent; its length is the slides'.
fit	Fit | null	How slides fill the canvas. Default cover.
fit_to	string | null	A sound file whose length the slides share out. It is not played: add it as a music bed.
id	string | null	The node's name, for other nodes to refer to.
itemsrequired	MediaItem[]	The slides.
ken_burns	number | null	How far each slide zooms in over its time, as a multiple: 1.15 ends 15% larger. Default none.
seconds	number | null	How long each slide shows, transitions included, in seconds. Default: fit_to's length shared out, else the theme's still length.
transition	TransitionChoice | null	What joins slides. Default theme.

type: "captioned_video"

A video under its captions.

Field	Type	Description
at	number | null	When it starts in its parent; its length is the video's.
captionsrequired	CaptionsNode	The captions, timed from the video's start.
fit	Fit | null	How the video fills the canvas. Default cover.
id	string | null	The node's name, for other nodes to refer to. Its sound is the video's.
videorequired	MediaItem	The video.

type: "title"

A title (and subtitle) over what is under it, laid out on the whole canvas.

Field	Type	Description
align	Align | null	Where it lies. Default center.
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
background	Rgba | null	A card's color. Default: the theme's surface.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
fade	number | null	Seconds of fade in and out. Default: the theme's.
id	string | null	The node's name, for other nodes to refer to.
subtitle	string | null	A smaller line under it.
textrequired	string	The title.

type: "title_card"

A title (and subtitle) on the theme's surface, over the whole canvas.

Field	Type	Description
align	Align | null	Where it lies. Default center.
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
background	Rgba | null	A card's color. Default: the theme's surface.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
fade	number | null	Seconds of fade in and out. Default: the theme's.
id	string | null	The node's name, for other nodes to refer to.
subtitle	string | null	A smaller line under it.
textrequired	string	The title.

type: "lower_third"

A name and role in the canvas's lower left.

Field	Type	Description
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
fade	number | null	Seconds of fade in and out. Default: the theme's.
id	string | null	The node's name, for other nodes to refer to.
subtitle	string | null	The role, under it.
textrequired	string	The name.

type: "end_card"

A closing card over the whole canvas: a logo, a title and a subtitle on the theme's surface.

Field	Type	Description
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
background	Rgba | null	The card's color. Default: the theme's surface.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
fade	number | null	Seconds of fade in and out. Default: the theme's.
id	string | null	The node's name, for other nodes to refer to.
logo	string | null	A picture above the title.
subtitle	string | null	A smaller line under it.
textrequired	string	The title.

type: "comparison_grid"

Clips side by side in a grid, each labeled.

Field	Type	Description
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
audio_from	integer | null	Which item's sound plays, by index. Default: none.
columns	integer | null	Columns. Default: as square a grid as the items make.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
gap	number (float)	Pixels between cells. Default: 0
id	string | null	The node's name, for other nodes to refer to.
itemsrequired	MediaItem[]	The clips, row by row; each one's label names its cell.
length	GridLength	How long the grid lasts when its clips differ. Default shortest. Default: "shortest"

type: "reframe"

A video fitted to a canvas of another shape, over a blurred copy of itself.

Field	Type	Description
at	number | null	When it starts in its parent; its length is the video's.
blur	number | null	The background's blur radius, as a fraction of its shorter side. Default 0.05.
id	string | null	The node's name, for other nodes to refer to. Its sound is the video's.
videorequired	MediaItem	The video.

type: "logo"

A picture in a corner.

Field	Type	Description
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
corner	Align | null	The corner. Default top-right.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
id	string | null	The node's name, for other nodes to refer to.
margin	number | null	Pixels from the edges. Default: the theme's margin.
opacity	number | null	Opacity, 0..=1. Default 1.
pathrequired	string	The picture.
size	number | null	Its longer side, in pixels. Default: 15% of the canvas's shorter side.

type: "music_bed"

Music under the video, faded in and out and ducked under speech.

Field	Type	Description
at	number | null	Seconds from the parent's start (an overlay's: the video's). Ignored in a sequence, which places its children one after another.
duck_depth_db	number | null	How far ducking lowers it, in dB (negative). Default -12.
duck_under	string | null	The id of a node (or body) whose sound it ducks under.
duration	number | null	Length in seconds. Default: the node's own (a video's, a caption file's), else what its parent gives it.
fade_in	number | null	Seconds of fade in. Default 1.
fade_out	number | null	Seconds of fade out at the end. Default 2.
id	string | null	The node's name, for other nodes to refer to.
loop	boolean	Plays the file again from its start while the video lasts. Default true. Default: true
pathrequired	string	The file.
volume	number | null	Linear gain. Default 1.

NodeId

A stable identifier of a node within one composition graph. It has no /, which joins the IDs of the group and media nodes a step was drawn through.

Type: string

NodeOp

The operation of a CompositionNode.

Animated settings are keyed in composition time (see ClipComposition), not timeline time.

One of:

type: "clip"

The picture of the clip showing the composition: its source at the source time the clip's time map gives, or what its generated source draws.

type: "media"

Another visual source, read at start plus the composition time. A media node adds no sound to the mix.

Field	Type	Description
source_idrequired	SourceId	The source; a video, image, or generated source.
start	MediaTime	Source time shown at composition time zero. Non-negative. Default: 0

type: "generator"

A picture the engine draws.

Field	Type	Description
generatorrequired	Generator	What is drawn.

type: "effect"

A registered effect: its input and the named images it samples besides.

Field	Type	Description
effectrequired	ClipEffect	The versioned effect and its parameters.
input	NodeId | null	The image the effect processes; a bypassed node passes it through. Default: null
inputs	{ [name]: NodeId | null }	The images the effect samples besides its input, by the names its definition declares (sample_<name> in its shader); at most MAX_EFFECT_INPUTS. A name the definition does not declare, or one it declares and this leaves out, fails the frames that draw the node.

type: "transition"

A registered two-input transition at an explicit progress.

Field	Type	Description
effectrequired	ClipEffect	The versioned transition and its parameters.
from	NodeId | null	The image at progress zero. Default: null
progressrequired	Animated_float	Progress through the transition, in 0..=1.
to	NodeId | null	The image at progress one. Default: null

type: "transform"

The input placed on the canvas by a transform and opacity.

Field	Type	Description
input	NodeId | null	The image placed. Default: null
transform	VisualProperties	Position, anchor, scale, rotation, and opacity. Default: {"anchor":{"x":0.5,"y":0.5},"opacity":{"mode":"constant",…

type: "merge"

Ordered layers composited over transparency.

Field	Type	Description
layers	MergeLayer[]	Layers from bottom to top. Default: []

type: "matte"

The input kept where a second image says.

Field	Type	Description
input	NodeId | null	The image kept. Default: null
matte	NodeId | null	The image whose alpha or luminance is coverage. Default: null
moderequired	MatteMode	Which property of the matte image is coverage.

type: "shape_mask"

The input kept inside shapes.

Field	Type	Description
input	NodeId | null	The image masked. Default: null
masksrequired	ShapeMask[]	The shapes, combined in order; at most MAX_CLIP_MASKS. Geometry is in the input image's normalized space.

type: "group"

Another composition drawn in this one's time, as a group: its output, with its group inputs fed from inputs and its controls set from controls.

Field	Type	Description
compositionrequired	CompositionId	The composition drawn.
controls	{ [name]: Animated_EffectValue }	Values for its controls, by name; a control not set keeps the composition's own value. Keyed in composition time.
inputs	NodeId | null[]	The image for each of its inputs, in its port order. Default: []

type: "group_input"

In a composition used as a group, the image the group node gives its input index.

Field	Type	Description
indexrequired	integer (uint32)	The input, in the composition's port order.

Overflow

Whether content past a box's padding box is drawn.

• "visible" Drawn.
• "hidden" Clipped to the padding box.

Paint

A color or gradient.

Gradients interpolate between stops premultiplied, in linear light: the engine's working space, so a gradient between two colors passes through the physical mix of them, and a stop fading to transparent does not darken its neighbour.

A color (hex or object) is read as a solid paint of it; a paint is written back tagged.

One of:

type: "solid"

One color.

Field	Type	Description
colorrequired	Rgba	The color.

type: "linear_gradient"

Colors along the line from start to end, constant across it.

Field	Type	Description
endrequired	Vec2	Where offset 1 lies. Distinct from start.
spread	Spread	What lies beyond the first and last offsets. Default: "pad"
startrequired	Vec2	Where offset 0 lies.
stopsrequired	GradientStop[]	Two to MAX_GRADIENT_STOPS stops.

type: "radial_gradient"

Colors along the radius of a circle.

Field	Type	Description
centerrequired	Vec2	Where offset 0 lies.
radiusrequired	number (float)	The distance of offset 1 from the centre, as a fraction of the picture's shorter side. Positive.
spread	Spread	What lies beyond the first and last offsets. Default: "pad"
stopsrequired	GradientStop[]	Two to MAX_GRADIENT_STOPS stops.

type: "conic_gradient"

Colors around a point: offsets 0 to 1 are one clockwise turn.

Field	Type	Description
angle_degrees	number (float)	Where offset 0 lies, in degrees clockwise from straight up. Default: 0
centerrequired	Vec2	The point the gradient turns around.
stopsrequired	GradientStop[]	Two to MAX_GRADIENT_STOPS stops.

<a href="#rgba">Rgba</a>

Path

One or more subpaths.

Field	Type	Description
subpathsrequired	Subpath[]	The subpaths, at most MAX_PATH_SUBPATHS, with at most MAX_PATH_VERTICES vertices among them.

PathVertex

A path vertex and its tangents. The segment from vertex a to vertex b is the cubic Bezier through a.point, a.point + a.out_tangent, b.point + b.in_tangent, and b.point; zero tangents make it straight.

Field	Type	Description
in_tangent	Vec2	The control point of the segment ending here, relative to point. Default: {"x":0,"y":0}
out_tangent	Vec2	The control point of the segment starting here, relative to point. Default: {"x":0,"y":0}
pointrequired	Vec2	Where the vertex lies.

PointKeyframe

One keyframe of an AnimatedPoint.

Field	Type	Description
in_tangent	Vec2	The end of the way here from the previous keyframe's value, relative to this value: that curve's second control point.
interpolationrequired	Interpolation	Interpolation from this keyframe to its successor: how fast the value travels along the way there.
out_tangent	Vec2	The start of the way to the next keyframe's value, relative to this value: the curve's first control point.
timerequired	MediaTime	Timestamp of this value, as a Keyframe's.
valuerequired	Vec2	Value at time.

PolystarKind

What kind of figure a polystar is.

• "star" Points joined by inner corners.
• "polygon" Points joined by straight sides.

Position

Whether a box is in its parent's flow.

• "relative" In the flow.
• "absolute" Out of the flow, placed by inset.

ProviderSource

A source whose media an extension provider supplies, rather than the host's video and image decoders.

A host picks the provider by probing the bytes at import, never by a file name, and records it here with the settings the source needs, so every host opens the source the same way. The engine does not read it: a provider source needs frames like any video or image source.

One of:

format: "svg"

A static SVG document, rasterized at the size it is shown. The source's kind is image.

format: "animated_image"

A GIF, animated WebP, or APNG: one cycle of frames, each with its own duration. Repetition is the clip's. The source's kind is video.

format: "lottie"

A Lottie animation, from a Lottie JSON file or a dotLottie package, evaluated at its own frames. The source's kind is video.

Field	Type	Description
animation	string | null	The dotLottie animation shown, by its ID; the package's first when absent, and absent for a Lottie JSON file.

format: "image_sequence"

Still images played in order at a fixed rate. The source's kind is video.

Field	Type	Description
frame_raterequired	FrameRate	The rate the frames play at.
framesrequired	string | null[]	Each frame's locator, in play order. null is a number missing from the sequence, allowed only when missing says how to show it.
missing	MissingFrames	How a missing frame is shown. Default: "reject"
primaries	LinearPrimaries | null	The primaries OpenEXR frames' linear RGB is in, overriding what the first frame's chromaticities say. Only for OpenEXR frames.
start_number	integer (uint64)	The number of the first frame, as its file was numbered. Default: 0

format: "exr"

A still OpenEXR image: linear-light RGB(A), read at half precision. The source's kind is image.

Field	Type	Description
primaries	LinearPrimaries | null	The primaries its linear RGB is in, overriding what the file's chromaticities say (BT.709 when it says nothing, as OpenEXR defines).

Rgba

A straight (not premultiplied), sRGB-encoded color with alpha, each component in 0..=1.

Written as the object, or as CSS hex: "#rgb", "#rgba", "#rrggbb" or "#rrggbbaa", any case, each digit pair a component times 255. It is written back as the object: a component need not be a multiple of 1/255.

One of:

object

Field	Type	Description
alpharequired	number (float)	Coverage.
bluerequired	number (float)	Blue component.
greenrequired	number (float)	Green component.
redrequired	number (float)	Red component.

string

ShapeGeometry

A geometry alone, as a mask's outline is.

One of:

type: "rectangle"

A rectangle, optionally with rounded corners.

Field	Type	Description
centerrequired	AnimatedPoint	Centre.
corner_radius	Animated_float	Corner radius, as a fraction of the shorter side. Non-negative; a radius past half the rectangle is capped. Default: {"mode":"constant","value":0}
rotation_degrees	Animated_float	Clockwise rotation about the centre, in degrees. Default: {"mode":"constant","value":0}
sizerequired	Animated_Vec2	Full width and height, before rotation, per axis: x a fraction of the picture's width, y of its height. Non-negative.

type: "ellipse"

An ellipse.

Field	Type	Description
centerrequired	AnimatedPoint	Centre.
rotation_degrees	Animated_float	Clockwise rotation about the centre, in degrees. Default: {"mode":"constant","value":0}
sizerequired	Animated_Vec2	Full width and height, before rotation, per axis: x a fraction of the picture's width, y of its height. Non-negative.

type: "polystar"

A regular polygon or star.

Field	Type	Description
centerrequired	AnimatedPoint	Centre.
inner_radius	Animated_float	A star's distance of its inner corners from the centre. Non-negative. Default: {"mode":"constant","value":0}
inner_roundness	Animated_float	How round a star's inner corners are, in 0..=1. Default: {"mode":"constant","value":0}
kindrequired	PolystarKind	A polygon or a star.
outer_radiusrequired	Animated_float	Distance of the points from the centre, as a fraction of the shorter side. Non-negative.
outer_roundness	Animated_float	How round the outer corners are: 0 sharp, 1 a smooth curve through them. In 0..=1. Default: {"mode":"constant","value":0}
pointsrequired	Animated_float	Number of points (corners of a polygon, tips of a star), from MIN_POLYSTAR_POINTS to MAX_POLYSTAR_POINTS. A fraction is dropped when drawn, as Lottie drops it, so an animated count changes the figure one whole point at a time.
rotation_degrees	Animated_float	Clockwise rotation about the centre, in degrees. Default: {"mode":"constant","value":0}

type: "path"

A Bezier path.

Field	Type	Description
pathrequired	Animated_Path	The path.

ShapeItem

One entry of a shapes generator's content tree.

A group is read front to back. Geometry accumulates in its group; a fill or a stroke paints the geometry listed before it in the same group, nested groups before it included; a trim cuts that geometry and replaces it. A paint listed earlier is drawn on top of one listed later, as in After Effects and Lottie.

One of:

type: "group"

Items drawn together, through one transform and opacity. Their geometry also counts as the enclosing group's, for the paints and trims after the group.

Field	Type	Description
itemsrequired	ShapeItem[]	The group's items, front first.
transform	ShapeTransform	Where the group lies, and how opaque it is. Default: {"anchor":{"mode":"constant","value":{"x":0,"y":0}},"opac…

type: "rectangle"

A rectangle, optionally with rounded corners.

Field	Type	Description
centerrequired	AnimatedPoint	Centre.
corner_radius	Animated_float	Corner radius, as a fraction of the shorter side. Non-negative; a radius past half the rectangle is capped. Default: {"mode":"constant","value":0}
rotation_degrees	Animated_float	Clockwise rotation about the centre, in degrees. Default: {"mode":"constant","value":0}
sizerequired	Animated_Vec2	Full width and height, before rotation, per axis: x a fraction of the picture's width, y of its height. Non-negative.

type: "ellipse"

An ellipse.

Field	Type	Description
centerrequired	AnimatedPoint	Centre.
rotation_degrees	Animated_float	Clockwise rotation about the centre, in degrees. Default: {"mode":"constant","value":0}
sizerequired	Animated_Vec2	Full width and height, before rotation, per axis: x a fraction of the picture's width, y of its height. Non-negative.

type: "polystar"

A regular polygon or star.

Field	Type	Description
centerrequired	AnimatedPoint	Centre.
inner_radius	Animated_float	A star's distance of its inner corners from the centre. Non-negative. Default: {"mode":"constant","value":0}
inner_roundness	Animated_float	How round a star's inner corners are, in 0..=1. Default: {"mode":"constant","value":0}
kindrequired	PolystarKind	A polygon or a star.
outer_radiusrequired	Animated_float	Distance of the points from the centre, as a fraction of the shorter side. Non-negative.
outer_roundness	Animated_float	How round the outer corners are: 0 sharp, 1 a smooth curve through them. In 0..=1. Default: {"mode":"constant","value":0}
pointsrequired	Animated_float	Number of points (corners of a polygon, tips of a star), from MIN_POLYSTAR_POINTS to MAX_POLYSTAR_POINTS. A fraction is dropped when drawn, as Lottie drops it, so an animated count changes the figure one whole point at a time.
rotation_degrees	Animated_float	Clockwise rotation about the centre, in degrees. Default: {"mode":"constant","value":0}

type: "path"

A Bezier path.

Field	Type	Description
pathrequired	Animated_Path	The path.

type: "fill"

Paints the inside of the geometry listed before it in its group, all of it as one compound path under rule. An open path is closed for it.

Field	Type	Description
opacity	Animated_float	Opacity in 0..=1. Default: {"mode":"constant","value":1}
paintrequired	Animated_Paint	What covers it.
rule	FillRule	Which regions of the compound path are inside. Default: "nonzero"

type: "stroke"

Strokes the geometry listed before it in its group.

Field	Type	Description
cap	LineCap	How open ends look. Default: "butt"
dash	Dash | null	Dashes, or a solid stroke when absent. Default: null
join	LineJoin	How segments meet. Default: "miter"
miter_limit	number (float)	Longest a miter join reaches, as a multiple of half the width, before it is beveled. At least 1. Default: 4
opacity	Animated_float	Opacity in 0..=1. Default: {"mode":"constant","value":1}
paintrequired	Animated_Paint	What covers the stroke.
widthrequired	Animated_float	Full width, as a fraction of the shorter side. Non-negative; zero draws nothing.

type: "trim"

Keeps part of the geometry listed before it in its group, by length.

Field	Type	Description
endrequired	Animated_float	Where it ends, in 0..=1. Nothing is kept unless it is after start.
mode	TrimMode	Whether the span is of all the geometry together or of each part. Default: "together"
offset	Animated_float	Turns the span is shifted by; it wraps around a closed path. Default: {"mode":"constant","value":0}
startrequired	Animated_float	Where the kept span starts, as a fraction of the length, in 0..=1.

ShapeMask

A shape that limits where a clip is visible.

Geometry is in the clip's source space, before its transform, so the mask moves with the clip: (0, 0) is the source's top-left corner and (1, 1) its bottom-right. Distances (feather, a rectangle's corner_radius, a polystar's radii) are fractions of that space's shorter side, so a mask covers the same part of the picture at any render resolution.

Field	Type	Description
feather	Animated_float	How soft the edge is. Non-negative; zero is the outline's antialiased edge. The coverage is blurred by a Gaussian of standard deviation 0.3125 * feather, which spreads its 10 to 90 percent ramp over 0.8 * feather across the outline. Default: {"mode":"constant","value":0}
fill_rule	FillRule	Which regions of the outline are inside it. Default: "nonzero"
invert	boolean	Whether the mask keeps the outside of the shape instead of its inside. Default: false
mode	MaskMode	How this mask combines with the ones before it. Default: "add"
shaperequired	ShapeGeometry	The shape's outline, as a shapes generator's geometry.

ShapeTransform

A group's placement: in pixel space, translate by position, rotate, scale, and translate by minus anchor, so anchor lands on position. The default leaves its items where they are.

Field	Type	Description
anchor	Animated_Vec2	The point of the items that is placed at position. Default: {"mode":"constant","value":{"x":0,"y":0}}
opacity	Animated_float	Opacity of the group as a whole, in 0..=1: overlapping items are composited first and faded together. Default: {"mode":"constant","value":1}
position	AnimatedPoint	Where anchor is placed. Default: {"mode":"constant","value":{"x":0,"y":0}}
rotation_degrees	Animated_float	Clockwise rotation, in degrees. Default: {"mode":"constant","value":0}
scale	Animated_Vec2	Per-axis scale; 1 leaves the items unscaled. Stroke widths scale with it. Default: {"mode":"constant","value":{"x":1,"y":1}}

SourceId

A stable media-source identifier.

Type: string

Spread

What a linear or radial gradient shows outside its first and last stops.

• "pad" The end colors continue.
• "repeat" The gradient starts again.
• "reflect" The gradient runs back and forth.

StreamTopology

The streams a media file carries.

Field	Type	Description
audio	AudioStreamShape | null	The primary audio stream, if there is one.
video	VideoStreamShape | null	The primary video stream, if there is one.

Subpath

A run of vertices joined by cubic Bezier segments.

Field	Type	Description
closed	boolean	Whether a segment joins the last vertex back to the first. Default: false
verticesrequired	PathVertex[]	The vertices, in order.

TextAlign

How lines of text align within it.

• "start" Left.
• "center" Centred.
• "end" Right.

TextBackground

A box behind each line of text.

Field	Type	Description
colorrequired	Rgba	Box color.
padding	number (float)	Space between the text and the box edge, as a fraction of the font size, in [0, 2]. Default: 0

TextOutline

A band around the glyphs, drawn behind them.

Field	Type	Description
colorrequired	Rgba	Band color.
widthrequired	number (float)	Band width as a fraction of the font size, in (0, 0.5].

TextRole

A theme text style.

• "title" The largest.
• "subtitle" Under a title.
• "body" Running text.
• "label" A cell's label.

TextStyle

How text looks and where it lies: a caption track's cues, or a text Generator.

Sizes are resolution-independent: the font size is a fraction of the canvas's shorter side, as every other length is, the wrapping width a fraction of the canvas width, and the outline and background padding fractions of the font size. The engine draws with the fonts its host registered: those of font_family first, then the rest in their fallback order.

Field	Type	Description
align	TextAlign	How lines align within the text. Default: "center"
anchor	Vec2	The point of the text, background included, placed at position: (0.5, 1) is its bottom centre. Default: {"x":0.5,"y":1}
background	TextBackground | null	A box behind each line. Default: null
color	Rgba	Text color. Default: {"alpha":1,"blue":1,"green":1,"red":1}
font_family	string | null	The family the text draws in, as the font's own name table gives it (typographic family, else family), matched without regard to ASCII case. Glyphs its fonts lack, and a family no registered font has, draw from the other fonts in fallback order. None draws from the fallback order alone. Non-empty, at most MAX_FONT_FAMILY_BYTES bytes.
font_size	number (float)	Font size as a fraction of the canvas's shorter side: positive, at most MAX_CAPTION_FONT_SIZE on a caption track and MAX_TEXT_GENERATOR_FONT_SIZE in a text generator. Default: 0.05
font_weight	integer (uint16)	The weight, in [1, 1000], a family's faces are matched by, as CSS Fonts 4 matches font-weight; a variable face draws at it, clamped to its wght axis. No face is emboldened: a weight the family lacks draws its nearest face. Default: 400
letter_spacing	number (float)	Space after each character, as a fraction of the font size, in [-0.5, 1], as CSS letter-spacing adds it: none after a line's last character, and none after a character of a cursive script (Arabic, say), whose joins it would break. Not zero, it turns optional ligatures off. Default: 0
line_height	number (float)	Baseline-to-baseline distance in font sizes, in [0.5, 3]. Each line's em box, 0.8 of a font size above its baseline and 0.2 below, is centred in its line when the line is taller than an em. Default: 1.2
max_width	number (float)	Width text wraps at, as a fraction of the canvas width, in (0, 1]. Default: 0.9
outline	TextOutline | null	A band around the glyphs. Default: null
position	Vec2	Where on the canvas the text's anchor lies, (0, 0) top-left to (1, 1) bottom-right. Default: {"x":0.5,"y":0.92}

Theme

How text, panels and timings look. Every part left out is the base theme's. Sizes are fractions of the canvas's shorter side, so a theme looks the same on a wide and a tall canvas.

Field	Type	Description
accent	Rgba | null	A highlight: a lower third's bar.
background	Rgba | null	The canvas background.
base	string | null	The built-in theme this one changes. Default clean-dark.
body_size	number | null	Body text size.
caption_size	number | null	Caption size.
fade_seconds	number | null	How long text and cards fade in and out, in seconds.
font_family	string | null	The family text draws in, as the font names it. Unset, text draws in the first font an export registers.
label_size	number | null	Label size: a grid cell's.
margin	number | null	The space kept clear at the canvas's edges.
panel	Rgba | null	The boxes behind labels, lower thirds and boxed captions.
still_seconds	number | null	How long a still shows when nothing says, in seconds.
subtitle_size	number | null	Subtitle size.
surface	Rgba | null	What title and end cards are drawn on.
text	Rgba | null	Text color.
text_seconds	number | null	How long a card or text shows when nothing says, in seconds.
title_size	number | null	Title size.
transition	Transition | null	The transition a slideshow, or a sequence asking for theme, puts between its children.

ThemeChoice

A theme by name, or one built on a named theme.

One of:

string

A built-in theme: clean-dark or clean-light.

<a href="#theme">Theme</a>

A theme of its own.

TimeMap

How a clip plays its source range over its timeline range.

forward and reverse stretch the source range over the timeline range, so their speed is the ratio of the two. A loop plays the source range at its own speed, again and again, for as long as the timeline range lasts.

One of:

type: "forward"

From the start of the source range to its end.

type: "reverse"

From the end of the source range to its start: pictures in reverse order and sound played backwards.

type: "freeze"

One source instant for the whole clip, and silence.

Field	Type	Description
source_timerequired	MediaTime	The instant shown; inside the source range.

type: "loop"

The source range again and again, at its own speed.

Field	Type	Description
moderequired	LoopMode	How each pass follows the one before.

TimeRange

A half-open timeline interval [start, end).

Field	Type	Description
endrequired	MediaTime	Exclusive end.
startrequired	MediaTime	Inclusive start.

TimeScale

A positive rational rate of one time against another.

Field	Type	Description
denrequired	integer (uint32)	Denominator; positive.
numrequired	integer (uint32)	Numerator; positive.

Track

A homogeneous visual or audio timeline lane.

Field	Type	Description
audio	TrackAudio	Bus controls applied to this track's mixed audio. Default: {"ducking":null,"effects":[],"gain":{"mode":"constant","v…
captions	Captions | null	The cues and style of a caption track; present exactly for that kind. Default: null
clips	Clip[]	Clips on this track. Ordering is authoring order; evaluation sorts by time. A caption track has none. Default: []
idrequired	TrackId	Stable track identity.
kindrequired	TrackKind	Controls source compatibility and evaluation behavior.
namerequired	string	User-visible track name.
transitions	ClipTransition[]	Explicit transitions between overlapping clips on this track. Default: []

TrackAudio

Per-track audio bus controls.

Field	Type	Description
ducking	Ducking | null	Optional sidechain attenuation driven by another track. Default: null
effects	AudioEffect[]	Ordered single-input effects applied to the summed clip signal, at most MAX_CHAIN_EFFECTS. Default: []
gain	Animated_float	Animated linear bus amplitude constrained to 0..=MAX_GAIN. Default: {"mode":"constant","value":1}
muted	boolean	Silences this bus. Default: false
pan	Animated_float	Animated stereo position applied after the clip mix, from -1 (left) to 1 (right). Default: {"mode":"constant","value":0}
solo	boolean	Restricts the mix to soloed buses when any track sets this. Default: false

TrackId

A stable timeline-track identifier.

Type: string

TrackKind

The media domain accepted by a track.

• "video" A composited visual track.
• "audio" A mixed audio track.
• "caption" Timed text, drawn over the tracks before it and under the ones after.

TrackList

A grid track list as CSS writes it: "1fr 2fr 120px", "repeat(3, minmax(100px, 1fr))", "repeat(auto-fill, 160px)", "auto min-content max-content", "fit-content(200px)". A bare number is a fraction of the picture's shorter side. Named lines are not supported.

Type: string

TransferFunction

Encoded transfer curve.

• "bt709" BT.709 opto-electronic transfer function.
• "srgb" IEC sRGB transfer function.
• "pq" Perceptual quantizer HDR transfer function.
• "hlg" Hybrid log-gamma HDR transfer function.

Transition

The transition between two neighbours of a sequence.

Field	Type	Description
durationrequired	number (double)	How long the neighbours overlap, in seconds.
easing	Easing | null	The timing curve. Default linear.
params	{ [name]: Animated_EffectValue }	The effect's parameters by name.
typerequired	string	crossfade, a built-in transition's short name (wipe-left, circle-open, ...), or a full effect id (alpha2.transition.fade).
version	integer | null	The effect definition's version. Default 1.

TransitionChoice

A sequence's transitions: none, the theme's, or one given.

One of:

string

none for cuts, theme for the theme's transition, or a transition name at the theme's duration.

<a href="#transition">Transition</a>

A transition.

TrimMode

What a trim measures.

• "together" One span over the length of every subpath end to end, in order.
• "individually" A span of each subpath alone.

Vec2

A two-dimensional value in normalized output coordinates.

Field	Type	Description
xrequired	number (float)	Horizontal component.
yrequired	number (float)	Vertical component.

VideoStreamShape

A video stream's displayed size and frame rate.

Field	Type	Description
frame_rate	FrameRate | null	The rate its first frames are presented at, as every host measures it from packet times and rounds it (alpha2_assets::FrameRateEvidence), when it can be measured. Not the rate a stream declares: a declared rate is a guess for variable-rate media, and browsers report none.
heightrequired	integer (uint32)	Displayed height in square pixels: the stored height stretched by a pixel aspect ratio taller than wide, then turned.
widthrequired	integer (uint32)	Displayed width in square pixels: the stored width stretched by a pixel aspect ratio wider than tall, then turned by the stream's orientation.

VisualProperties

Resolution-independent visual presentation controls for a clip.

Each field a document leaves out takes its default: the source centred on the canvas, unscaled, unrotated and opaque.

Field	Type	Description
anchor	Vec2	Unanimated normalized point within the source rectangle. Default: {"x":0.5,"y":0.5}
opacity	Animated_float	Animated opacity constrained to 0..=1. Default: {"mode":"constant","value":1}
position	AnimatedPoint	Animated normalized canvas translation, along spatial curves where its keyframes have tangents. Default: {"mode":"constant","value":{"x":0.5,"y":0.5}}
rotation_degrees	Animated_float	Animated clockwise rotation in degrees. Default: {"mode":"constant","value":0}
scale	Animated_Vec2	Animated per-axis scale. Default: {"mode":"constant","value":{"x":1,"y":1}}