Preview and browser export

Live preview, still capture, and video export use the same composition graph, fixed-step clock, and audio-frame contract. Identical timestamps and seeds produce equivalent frames within the renderer tolerance.

Sonic Weaver encodes with WebCodecs where the browser provides it and falls back to the browser's own MediaRecorder, which produces WebM. There is no FFmpeg or WASM transcode: that route was removed because it could never load behind this site's Content Security Policy and its encoder core is GPL licensed. Supported desktop hardware may export up to 4K. Constrained phones are limited to 1080p to avoid failed or corrupted exports.

Why an export may be WebM instead of MP4: the Export panel checks whether this browser can encode compatible H.264 video and AAC audio. MP4 is selectable only when both encoders are available; otherwise MP4 is disabled and the export uses WebM. The downloaded extension matches the actual format. For an MP4, use a browser and device where the Export panel enables MP4; the editor export does not convert a completed WebM file to MP4.

Rendering remains on your device; there is no cloud-render queue. Audio inclusion, trims, captions, platform dimensions, frame rate, and alpha support depend on the selected format.