1. Fully qualified codec strings

The codec string begins with the prefix "hev1." or "hvc1.", with a suffix of four dot-separated fields as described in Section E.3 of [iso14496-15].

2. EncodedVideoChunk data

EncodedVideoChunk [[internal data]] is expected to be an access unit as defined in [ITU-T-REC-H.265] section 7.4.2.4.

NOTE: An access unit contains exactly one base layer coded picture.

If the bitstream is in hevc format, [[internal data]] is assumed to be in canonical format, as defined in [iso14496-15] section 8.3.2.

If the bitstream is in annexb format, [[internal data]] is assumed to be in Annex B format, as defined in [ITU-T-REC-H.265] Annex B.

NOTE: Since [[internal data]] is inherently byte-aligned, implementations are not required to recover byte-alignment.

3. VideoDecoderConfig description

If the description is present, it is assumed to be an HEVCDecoderConfigurationRecord, as defined by [iso14496-15], section 8.3.3.1, and the bitstream is assumed to be in hevc format.

NOTE: This format is commonly used in .MP4 files, where the player generally has random access to the media data.

If the description is not present, the bitstream is assumed to be in annexb format.

NOTE: "annexb" format is described in greater detail by [ITU-T-REC-H.265], Annex B. This format is commonly used in live-streaming applications, where including the VPS, SPS, and PPS data periodically allows users to easily start from the middle of the stream.

4. EncodedVideoChunk type

If an EncodedVideoChunk’s [[type]] is key, and the bitstream is in hevc format, then the EncodedVideoChunk is expected to contain a base layer primary coded picture that is an instantaneous decoding refresh (IDR), clean random access (CRA), or broken link access (BLA) picture.

NOTE: If the bitstream is in hevc format, parameter sets necessary for decoding are included in VideoDecoderConfig.description.

If an EncodedVideoChunk’s [[type]] is key, and the bitstream is in annexb format, then the EncodedVideoChunk is expected to contain both a base layer coded picture that is an instantaneous decoding refresh (IDR), clean random access (CRA), or broken link access (BLA) picture, and all parameter sets necessary to decode all video data NAL units in the EncodedVideoChunk.

5. VideoEncoderConfig extensions

 partial   dictionary   VideoEncoderConfig  {
   HevcEncoderConfig   hevc ;
};

hevc , of type HevcEncoderConfig

Contains codec specific configuration options for the HEVC (H.265) codec.

5.1. HevcEncoderConfig

 dictionary    HevcEncoderConfig   {
   HevcBitstreamFormat   format  = "hevc";
};

format , of type HevcBitstreamFormat, defaulting to "hevc"

Configures the format of output EncodedVideoChunks. See HevcBitstreamFormat.

5.2. HevcBitstreamFormat

 enum    HevcBitstreamFormat   {
   "annexb" ,
   "hevc" ,
};

The HevcBitstreamFormat determines the location of HEVC parameter sets, and mechanisms for packaging the bitstream.

annexb

Parameter sets are included periodically throughout the bitstream.

NOTE: This format is described in greater detail by [ITU-T-REC-H.265], Annex B. This format is commonly used in live-streaming applications, where including the parameter set data periodically allows users to easily start from the middle of the stream.

hevc

Parameter sets are not included in the bitstream and are instead emitted via the [[output callback]] as the description of the EncodedVideoChunkMetadata.decoderConfig.

NOTE: This format is described in greater detail by [iso14496-15], section 8.3. This format is commonly used in .MP4 files, where the player generally has random access to the media data.

6. VideoEncoderEncodeOptions extensions

 partial   dictionary   VideoEncoderEncodeOptions  {
   VideoEncoderEncodeOptionsForHevc   hevc ;
};

hevc , of type VideoEncoderEncodeOptionsForHevc

Contains codec specific encode options for the [ITU-T-REC-H.265] codec.

6.1. VideoEncoderEncodeOptionsForHevc

 dictionary    VideoEncoderEncodeOptionsForHevc   {
   unsigned   short ?  quantizer ;
};

quantizer , of type unsigned short, nullable

Sets per-frame quantizer value. In [ITU-T-REC-H.265] the quantizer threshold can be varied from 0 to 51.

7. Privacy Considerations

Please refer to the section Privacy Considerations in [WEBCODECS].

8. Security Considerations

Please refer to the section Security Considerations in [WEBCODECS].