What is supported today?
This page answers what can be built with 1.2.0 and what is still a negotiated or uncertified
boundary. Exact symbols are in the generated API Reference and SDK API snapshot.
Basic editor
Section titled “Basic editor”The public SDK can register local/remote/OPFS media, create/load Project v1, render to Canvas, play and seek with audio, edit with transactions/history, persist canonical snapshots, and export locally or through an application remote provider.
Timeline editing
Section titled “Timeline editing”Supported semantic operations include move, trim, split, ripple, roll, slip, slide, linked A/V, track add/remove/reorder/lock/visibility, audio mute/solo, markers, revision conflict detection, interaction history grouping, undo, and redo. Commands fail atomically when source handles, ownership, locks, transitions, or mapping rules cannot be preserved.
Time, animation, and rate
Section titled “Time, animation, and rate”Time is integer microseconds with rational frame rates and half-open ranges. Items support source
mapping, linear rate, curve time-mapping (authored through the builder or compiled from a rate
envelope via buildRateEnvelope), transforms/opacity, keyframes/easing, and validated transition
intervals. Unsupported edit policies for complex mapping/animation fail closed.
Visual composition
Section titled “Visual composition”Project/Composition can represent media, images, text, shapes, captions, nested sequences, masks,
effects, transitions, generators, transforms, blend/composite behavior, and Materials. Image
sequences (uniform-duration still frames) are modeled as image-sequence Assets and sampled
deterministically through the frame mapping. Captions are first-class: SRT and WebVTT import and
export, caption tracks with styled clips, and silence-aware cue alignment. Preview and export share
Render IR semantics.
Current local color execution is RGBA8 SDR. P3/HDR metadata and capability contracts exist, but production HDR output is not yet certified and must not be inferred from API presence.
Preview and playback
Section titled “Preview and playback”Canvas preview supports exact-time render, stale-request cancellation, adaptive/full quality, fit/coordinate mapping, worker compositing, direct frame ownership, thumbnails, and statistics. Player supplies play/pause/seek, AudioWorklet timing, bounded shared/transferable transport, video scheduling, diagnostics, and cleanup.
Supported paths include source decode, PCM mix, gain/fades, track mixing, playback timing,
waveforms/analysis, silence workflows, ducking/master settings, and WAV/RF64 export. Offline
analysis adds beat detection and audio-energy change candidates through
SessionAudioController.analyzeBeats() / analyzeAudioEnergyChanges(). The deprecated
analyzeScenes() alias inspects audio only and must not be presented as pixel-based video scene
detection. Exact encoded audio support is negotiated inside MP4/WebM profiles.
Media input and cache
Section titled “Media input and cache”Production media supports File, URL/Range, OPFS, custom byte sources, MP4/MOV/MKV/TS/WebM indexing,
VideoFrame/PCM decode, AVIF/JPEG/PNG/WebP stills, proxy representations (including automatic proxy
registration through an injected encoder via registerAutomaticProxy), cache budgets, admission
queues, cancellation, and resource statistics. Large proxy sources require the range-reader
encoder contract; the legacy whole-buffer path fails above its configured memory limit. CDN
CORS/range correctness remains a deployment responsibility.
Export
Section titled “Export”Profiles cover H.264/AAC, AV1/AAC, and HEVC/AAC MP4; VP9/Opus WebM; PNG/JPEG/WebP; GIF; and WAV/RF64. Exact preflight checks codecs, color, channels, Materials, dimensions, and sink. Sinks include bounded memory, OPFS, custom writable targets, checkpointed muxed export, and remote providers.
Materials
Section titled “Materials”The SDK includes typed declarative graphs, Core Nodes, definitions/instances, deterministic
packages, integrity/signature/trust, catalog/registry, migrations, Material Lab, golden testing,
WebGL2/WebGPU compilation, budgets, and restricted trusted Shader/WASM policy. The WebGL2 and
WebGPU compilers share the full single-pass node set; multi-pass blur.gaussian graphs compile on
WebGL2 and fail closed on WebGPU (which lacks the multi-pass pipeline).
Boundaries that are not universal promises
Section titled “Boundaries that are not universal promises”- Exact WebCodecs encoder/decoder configurations vary by browser, OS, hardware, and settings.
- WebGPU, OPFS, SharedArrayBuffer, AV1, HEVC, 4K, and HDR are capability-negotiated.
- Physical Safari/iOS/Android and broad real-device matrices need continuing certification.
- Long background jobs are constrained by page/mobile lifecycle; use remote export when durability must exceed it.
- The SDK is engine infrastructure, not a complete product UI, collaboration backend, asset service, or cloud renderer.
Run probes and export preflight on the actual target with representative media. See Compatibility and deployment and Performance and resource budgets.