WebCodecs Origin Trial in Chrome 93: Breaking changes and new features

[Chris Cunningham]

To WebCodecs origin trial / experimental users: 

Chrome 93 is expected to release to stable channel on August 31st. Please see below for breaking changes and new features for WebCodecs in this release. 

We know this is a long list! Apologies for the disruption. WebCodecs will ship in M94, which means we'll send one final email of this sort (but shorter) for M94. 

Breaking changes in M93

• VideoFrame

• VideoFrame.readInto() is renamed to VideoFrame.copyTo() for consistency with other interfaces.

• The VideoFrame Planes interface is entirely deleted, including the VideoFrame planes attribute and the VideoFrame planes constructor. 

• frame.planes.readInto() is replaced by frame.copyTo(dest, ...), offering simpler and more efficient readback. 

• new VideoFrame(planes, ...) is replaced by new VideoFrame(BufferSource data, ...).

• VideoFrameRegion is replaced by DOMRect for better coherence with other APIs. Attribute / dictionary names are updated to match. 

• VideoFrame visibleRegion and codedRegion are renamed to visibleRect and codedRect, both returning a DOMRectReadOnly.

• VideoFrameCopyToOptions rect is now a DOMRectInit

• Attributes cropLeft, cropTop, cropWidth, and cropHeight are all removed in favor of visibleRect.

• VideoPixelFormat names are updated to be more intuitive / descriptive.

• RGB format names have been reversed such that letter order in the name now matches channel order in the array (e.g. RGBA = [R, G, B, A, ...])

• A new YUV format, I420A, was added for I420 + an alpha plane.

• VideoFrames created from Canvas will now be RGBA when constructed with alpha=keep. This is not formally a break (folks should always be prepared to handle any VideoPixelFormat, including `null` for unknown), but worth noting. Users should instead use alpha=discard if they don't need alpha data.  

• AudioData

• Everything changed! AudioData was completely redesigned, decoupling from WebAudio's AudioBuffer to offer lower level audio primitives. 

• Encoded{Audio|Video}Chunk

• These interfaces were made immutable, removing the chunk.data attribute in favor of a chunk.copyTo(dest) method. 

• VideoEncoder

• We implemented VideoEncoderConfig.bitrateMode, which defaults to "variable" bitrate. Sites that desire "constant" bitrate should now take care to set this field accordingly. Previously, the default behavior was platform/codec specific.

• VideoDecoder

• The VideoDecoderConfig members displayWidth, displayHeight, and all crop* members were removed. They are replaced by new attributes displayApsectWidth and displayAspectHeight.

• The chunk provided to decode(chunk) following any call to flush() or configure() must be a key frame. Failing to provide a key frame will throw a DataError.

• General

• [EnforceRange] is now added to numeric dictionary members. Out of range values will cause an exception to be thrown (ex: VideoDecoderConfig's codedWidth must be in the range of unsigned long)

• We've updated a few input validation exceptions to throw TypeError rather than ConstraintError, matching the spec.

Noteworthy additions in M93

• DevTools support for WebCodecs usage in DedicatedWorkers (Window already supported)

• AudioDecoding support for "alaw" and "mulaw" PCM

• VideoFrame color space metadata 

• Encoded{Audio|Video}Chunks are serializable, meaning you can postMessage(chunk)

Best,
Chris