New features and enhancements

• mkvmerge: AVC/h.264 parser: mkvmerge will now drop all frames before the first key frame as they cannot be decoded properly anyway. See #1908.
• mkvmerge: HEVC/h.265 parser: mkvmerge will now drop all frames before the first key frame as they cannot be decoded properly anyway. See #1908.
• mkvmerge: HEVC/h.265 parser: added a workaround for invalid values for the "default display window" in the VUI parameters of sequence parameter sets. Fixes #1907.

Bug fixes

• mkvmerge: MP4 reader: fixed track offsets being wrong in certain situations regarding the presence or absence of edit lists ('elst' atoms) & composition timestamps ('ctts' atoms). Fixes #1889.
• mkvmerge: MP4 reader: offsets in "ctts" are now always treated as signed integers, even with version 0 atoms.
• mkvinfo: the timestamps of SimpleBlocks with negative timestamps are now shown correctly.
• mkvmerge: Matroska reader: fixed handling BlockGroups and SimpleBlocks with negative timestamps.
• mkvmerge: MP3 packetizer: the MP3 packetizer will no longer drop timestamps from source containers if they go backwards. This keeps A/V in sync for files where the source was in sync even though their timestamps aren't monotonic increasing. Fixes #1909.
• mkvmerge: AVC/h.264 parser: mkvmerge will now drop timestamps from the source container if no frame is emitted for that timestamp. Fixes #1908.
• mkvmerge: HEVC/h.265 parser: mkvmerge will now drop timestamps from the source container if no frame is emitted for that timestamp. Fixes the HEVC equivalent of the problem with AVC described in #1908.
• mkvextract: SSA/ASS: fixed extraction when the "Format" line in the "[Events]" section contains less fields than the default for SSA/ASS would indicate. Fixes #1913.