v0.55.0

Added

• Dec3Box.JOCComplexity from the JOC (Joint Object Coding) extension of the dec3 box
  (ETSI TS 103 420 C.3) to detect Dolby Atmos in E-AC-3 tracks
• avc.CreateSEINalu and hevc.CreateSEINalu to build a full SEI NAL unit (codec
  NAL header + EBSP payload) from sei.SEIMessage values; the encode-side inverse of
  ParseSEINalu
• tkhd: the transformation matrix is parsed into TkhdBox.Matrix and preserved
  on encode, so rotation metadata survives round trips; a zero-value Matrix
  still encodes as the unity matrix. New helper mp4.UnityMatrix()
• AV1 metadata OBUs in the av1 package, in reusable layers: MetadataOBU
  (metadata_type + payload) with ParseMetadataOBU, ParseMetadataOBUFromOBU,
  Encode and Size, handling the mandatory trailing_bits and the reverse scan
  for the last non-zero payload byte (AV1 spec 6.7.1), and MetadataType constants
  for HDR CLL/MDCV, scalability, ITU-T T.35 and timecode. A payload that is not
  byte-aligned shares its last byte with trailing_bits; PayloadHasTrailingBits
  marks it so that Encode does not add a second trailing_one_bit
• av1.ITUTT35 for the metadata_itu_t_t35 body (country code, its 0xff
  extension byte, and payload) with ParseITUTT35, Encode, Size and
  MetadataOBU; it carries CTA-608 captions as well as HDR10+
• CTA-608 closed captions in AV1: av1.CreateCTA608MetadataOBU builds a complete
  caption metadata OBU from a cc_data() structure and av1.ExtractCTA608 reads the
  field 1 and field 2 byte pairs back from the OBUs of a temporal unit, plus
  ITUTT35.ITUData and ITUTT35.CTA608CCData. The payload is identical to the
  AVC/HEVC SEI one, so only the envelope differs between the codecs
• sei.CreateCTA608SEIMessage builds a CTA-608 user_data_registered_itu_t_t35
  (type 4) SEI message from a cc_data() structure, the encode-side counterpart of
  sei.ExtractCTA608sei. Wrap it with avc.CreateSEINalu or hevc.CreateSEINalu.
  Supporting helpers: sei.CTA608ITUData, sei.CreateCTA608Payload,
  sei.ITUData.Encode and sei.ITUDataSize
• Motion JPEG support: mjpg sample entry (JPEG image sequences, ISO/IEC 23008-12 Annex H)
  with the jpgC (JPEGConfigurationBox) and fiel (field handling) boxes.
  mp4.TrakBox.SetMJpegDescriptor creates an mjpg sample entry with an optional jpgC JPEG prefix
• Decode support for the legacy motion JPEG sample entries mp4v (with esds JPEG object type,
  ISO/IEC 14496-14) and jpeg (QuickTime), and Esds child access in VisualSampleEntryBox

Changed

• CEA-608 is renamed to its current designation CTA-608 in the sei API:
  sei.CEA608sei, sei.ParseCEA608, sei.ExtractCEA608sei and
  sei.ITUData.IsCEA608 become sei.CTA608sei, sei.ParseCTA608,
  sei.ExtractCTA608sei and sei.ITUData.IsCTA608. This is a breaking change; the
  old names are gone

Fixed

• avcC encode now writes the 4 trailing-info bytes for all AVC profiles outside
  66/77/88, symmetric with Size() and decode (e.g. profile 244)
• unknown bytes after the avcC trailing info are preserved through decode/encode
  in the new DecConfRec.TrailingBytes field instead of being dropped
• visual sample entries with a too long compressor name length byte are decoded
  by clamping the length to 31 like ffmpeg does, instead of failing
• Panic in hevc.ParseSEINalu and avc.ParseSEINalu on NAL units shorter than
  the codec's NAL unit header (e.g. an empty or single-byte HEVC SEI NALU);
  such input now returns ErrNotSEINalu
• sei.DecodeUserDataRegisteredSEI, sei.ExtractCTA608sei and sei.ParseCTA608 no
  longer panic on a short/truncated type-4 (user_data_registered_itu_t_t35) SEI
  payload; they return an error that propagates through avc/hevc.ParseSEINalu
• the build date in the --version output of the command line tools is rendered in
  UTC, so that a commit made close to midnight is no longer reported as the
  neighbouring day for users west of UTC