Transparent formats and playback compatibility
Choose PNGs, sprites, WebM Alpha, or ProRes 4444, and distinguish source transparency, encoded Alpha, and actual playback support.
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Transparency has three checkpoints
A transparent result needs a suitable source/processing path, an output format that carries Alpha, and a player or renderer that uses it. Passing one checkpoint does not prove the other two.
For the public API/MCP workflow, start from meaningful-Alpha images, use video.transparency.mode: "alpha_key", and enable transparent export. This is not arbitrary-background removal. The original generated video uses a temporary key-color background and remains opaque.
Select a format for the destination
| Output | Current encoding or structure | How to verify |
|---|---|---|
| PNG frames ZIP | Individual RGBA frames | Inspect representative frames on light and dark backgrounds |
| Spritesheet / engine pack | PNG plus frame/engine metadata | Check texture Alpha and the engine's material/import settings |
| WebM Alpha | VP8 with Alpha metadata | Test the actual browser, OS, device, and decoder used by the app |
| ProRes 4444 | Alpha-capable ProRes in MOV | Use an editor/compositor that supports this profile |
| Clip MP4 / original video | Opaque video | Do not expect transparency from this file |
The service's WebM Alpha encoder currently uses VP8, not VP9. A generic “WebM supported” indicator does not establish support for Alpha in this exact combination. ProRes 4444 is an editing/interchange option, not a promise of inline playback in every browser.
File extensions alone are insufficient. An arbitrary MOV or PNG may be opaque, and the same transparent file can appear on black in one viewer and composite correctly in another.
Diagnose with the same frames
- Select a small representative range containing motion and fine edges.
- Export PNG frames alongside the destination format when your entitlement and quote permit.
- Compare the same frame on white, dark gray, and a contrasting color.
- If the PNG has correct Alpha but the video/player does not, investigate decoding or compositing before regenerating motion.
- If all outputs have the same opaque region, inspect source mode, export transparency, canvas background, and source Alpha.
A checkerboard baked into the source image is not transparency. Likewise, merely choosing a transparent output canvas cannot remove an opaque background inside each frame.
Inspect edges, not just the empty corners
Check hair, smoke, semitransparent clothing, motion blur, and colors close to the key background. Halos can come from source contamination, key-color spill, scaling, filtering, or the target application's Alpha interpretation.
Use the original export first when comparing; avoid an intermediate converter that might flatten Alpha. For engine textures, investigate filtering, compression, and material settings on the target platform. Changing a filename will not fix a lost channel.
An export verification failure can coexist with usable partial assets. Preserve those files and inspect the reported issue; do not call the whole workflow successful just because a video was produced.
Budget and deliverables
Advanced formats require export entitlement, and processing may consume credits. A short compatible test should precede a large delivery. Keep a portable PNG baseline and the matching metadata when a downstream pipeline needs a fallback.
Continue with output formats and transparent export troubleshooting. The documentation does not certify every browser or engine version; validate your actual target environment.
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