v0.54.0

Added

• AV1 bitstream parsing in the av1 package: OBU splitting (SplitOBUs,
  ParseOBUHeader, ReadLEB128), sequence headers (ParseSequenceHeader,
  SequenceHeader, CodecConfRec.SequenceHeader), frame-header decoding
  (FrameHeaderDecoder, FrameHeader) with per-frame resolution and tile layout,
  random-access detection (FrameType, ParseFrameHeaderStart, IsRAPSample) and
  tile-data location (GetTileRanges, verified byte-exact against shaka-packager)
• AV1 RFC 6381 codecs string: CodecConfRec.CodecString, SequenceHeader.CodecString
  and av1.CodecString; the av1C box Info and mp4ff-pslister now show the
  sequence header, coded resolution, color configuration and codecs string for av01
• AV1 common encryption (cenc/cbcs): mp4.GetAV1ProtectRanges protects only tile data
  (OBU/frame/tile-group headers and tile-size fields stay clear) per the AV1 ISOBMFF
  binding; mp4ff-encrypt/mp4ff-decrypt support av01 tracks
• EncryptFragments and FragmentEncryptor (from InitProtectData.NewFragmentEncryptor)
  encrypt a decode sequence with a fresh per-sequence sample protector; InitProtectData is
  immutable and safe to share across goroutines
• ivf package to read and write the IVF container used for raw VP8/VP9/AV1 bitstreams (the
  VPx/AV1 counterpart of Annex B), and an ivf-to-mp4 example that muxes AV1 and VP9 IVF files
  into fragmented MP4. Supported by av1.OBU.Encode/Size, av1.CodecConfRecFromSequenceHeader
  and mp4.TrakBox.SetAV1Descriptor
• vp9 package parsing the VP9 uncompressed frame header (key-frame/random-access detection,
  color configuration and picture size) with vpcC level computation, plus
  mp4.TrakBox.SetVPxDescriptor to build vp08/vp09 sample entries from a vpcC box
• vp8 package parsing the VP8 frame tag and key-frame header (key-frame detection and picture
  size); ivf-to-mp4 now also muxes VP8 IVF into fragmented MP4

Fixed

• Panic in hevc.ParseSPSNALUnit on malformed input where cpb_cnt_minus1 in
  the sub-layer HRD parameters is 255 (found by fuzzing)