MKVToolNix 81.0 “Milliontown”

# Version 81.0 "Milliontown" 2023-12-02

## New features and enhancements

* mkvmerge: MPEG transport stream reader: HEVC/H.265: added support for
  reading single-layer Dolby Vision from Annex B type bitstream read from MPEG
  transport streams. Partially implements #3113.
* mkvmerge: MPEG transport stream reader, HEVC/H.265 elementary stream reader:
  added support for reading dual-layer Dolby Vision with both the base &
  enhancement layers in the same track from Annex B type bitstreams in MPEG
  transport files & elementary stream files. Implements #3126.
* mkvmerge: MPEG transport stream reader: HEVC/H.265: implemented combining
  dual-layer Dolby Vision with base & enhancement layers in different
  tracks. Implements #3127.
* MKVToolNix GUI: multiplexer: added a new option in the preferences for
  always enabling 'forced' subtitle tracks. A subtitle track is considered to
  be 'forced' if: the corresponding property is set in the source file; the
  track's name contains the word 'forced' (in English); deriving the 'forced
  display' flag from file names is active & the file name matches the
  corresponding pattern. The option is disabled by default. Implements #3627.
* MKVToolNix GUI: multiplexer: the functionality for detecting file name
  sequences when adding files can now recognize the patterns used by GoPro's
  cameras for chaptered video files. Implements #3633.
* xyzvc_dump: the end position of the current NALU will be output in
  non-portable format as well.
* xyzvc_dump: HEVC: the tool will now also output the inner NALU type of Dolby
  Vision NALUs (`unspec62` and `unspec63`).

## Bug fixes

* mkvmerge: when the user requests processing be stopped after the video ends
  `mkvmerge` will now take appending files into account properly. It won't
  stop processing unconditionally after the first file ends anymore. Fixes
  #3618.
* mkvmerge: AV1 handling in readers: the readers will now provide the pixel
  dimensions to the AV1 packetizer as early as possible, just like for other
  video packetizers. That way the pixel dimensions are available for
  calculating the display dimensions when command-line options such as
  `--aspect-ratio` & `--aspect-ratio-factor` are used. Before the change the
  calculation was done based on initial pixel dimension values of 0x0,
  resulting in display dimensions of 0x0, too. Fixes #3611.
* mkvmerge: HEVC/H.265 packetizer: when reading & appending HEVC/H.265 from
  Matroska, MP4/MOV or FLV files the first frame of all the appended files was
  sometimes dropped, resulting in broken video at the point where video is
  appended. Fixes #3479.
* mkvmerge: MPEG transport stream reader: when reading MPEG transport streams
  from Blu-rays the four-byte long `TP_extra_header` structure in front of the
  transport packets are now skipped properly. Before the fix a stray byte with
  value of `0x47` inside that `TP_extra_header` structure could have thrown
  off the detection of where the transport packets start, leading to mkvmerge
  dropping a few audio and/or video frames at the start of the file. Fixes
  #3632.
* mkvextract: AAC extractor: when an invalid program config element in the
  GA-specific config element is encountered, the program config element will
  be disregarded, which avoids mkvextract aborting with an exception. Fixes
  #3606.
* xyzvc_dump: fixed the tool aborting with an exception when the last NALU in
  an Annex B type file was shorter than four bytes.

## Other changes

* AVC & HEVC dumper development tool: the tool has been renamed from
  `xvc_dump` to `xyzvc_dump` as `xvc` is an abbreviation for an existing video
  codec (Extreme Video Coding), and the tool has nothing to do with that
  codec.