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• avformat/matroskaenc : Ensure that ChapterUID are != 0

  26 novembre 2019, par Andreas Rheinhardt

  avformat/matroskaenc : Ensure that ChapterUID are != 0
  AVChapters have an int as id field and therefore this value can appear
  
  <= 0. When remuxing from Matroska, this value actually contains
  
  the lower 32 bits of the original ChapterUID (which can be 64 bits).
  In order to ensure that the ChapterUID is always > 0, they were offset
  
  as follows (since 07704c61) : First max(0, 1LL - chapter[i].id) was computed
  
  and stored in an uint32_t. And then the IDs were offset using this value.
  This has two downsides :
  
  1. It does not ensure that the UID is actually != 0 : Namely if there is
  
  a chapter with id == INT_MIN, then the offset will be 2^31 + 1 and a
  
  chapter with id == INT_MAX will become 2^31 - 1 + 2^31 + 1 = 2^32 = 0,
  
  because the actual calculation was performed in 32 bits.
  
  2. As soon as a chapter id appears to be negative, a nontrivial offset
  
  is used, so that not even a ChapterUID that only uses 32 bits is
  
  preserved.
  So change this by treating the id as an unsigned value internally and
  
  only offset (by 1) if an id vanishes. The actual offsetting then has to
  
  be performed in 64 bits in order to make sure that no UINT32_MAX wraps
  
  around.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c

• avformat/matroskaenc : Move adding SeekEntry into end_ebml_master_crc32()

  27 avril 2020, par Andreas Rheinhardt

  avformat/matroskaenc : Move adding SeekEntry into end_ebml_master_crc32()
  Up until now, SeekEntries were already added before
  
  start_ebml_master_crc32() was even called and before we were actually
  
  sure that we really write the element the SeekHead references : After
  
  all, we might also error out later ; and given that the allocations
  
  implicit in dynamic buffers should be checked, end_ebml_master_crc32()
  
  will eventually have to return errors itself, so that it is the right
  
  place to add SeekHead entries.
  The earlier behaviour is of course a remnant of the time in which
  
  start_ebml_master_crc32() really did output something, so that the
  
  position before start_ebml_master_crc32() needed to be recorded.
  
  Erroring out later is also not as dangerous as it seems because in
  
  this case no SeekHead will be written (if it happened when writing
  
  the header, the whole muxing process would abort ; if it happened
  
  when writing the trailer (when writing chapters not available initially),
  
  writing the trailer would be aborted and no SeekHead containing the
  
  bogus chapter entry would be written).
  This commit does not change the way the SeekEntries are added for those
  
  elements that are output preliminarily ; this is so because the SeekHead
  
  is written before those elements are finally output and doing it
  
  otherwise would increase the amount of seeks.
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavformat/matroskaenc.c

• FFmpeg video metadata change

  5 avril 2022, par Warren

  I am trying to change the video stream metadata. See (Change This Metadata) below. I can change the title of the movie ok but not any others. What is the ffmpeg line to change this.

  



  This line below changes "Title Of The Movie" only

  



  ffmpeg -i Input.mkv -metadata title="New Title" -c:v copy -c:a copy -c:s copy Output.mkv

  



  Input #0, matroska,webm, from 'Input.mkv':
Metadata:
title           : Title Of The Movie
encoder         : libebml v1.2.3 + libmatroska v1.3.0
creation_time   : 2014-08-02 12:58:30
Duration: 02:15:54.21, start: 0.000000, bitrate: 8177 kb/s
Chapter #0.0: start 0.000000, end 208.666778
Metadata:
  title           : Chapter 01
Chapter #0.1: start 208.666778, end 811.727578
Metadata:
  title           : Chapter 02
Chapter #0.2: start 811.727578, end 1077.868444
Metadata:
  title           : Chapter 03
Chapter #0.3: start 1077.868444, end 1345.302289
Metadata:
  title           : Chapter 04
Chapter #0.4: start 1345.302289, end 2000.415067
Metadata:
  title           : Chapter 05
Chapter #0.5: start 2000.415067, end 2487.276444
Metadata:
  title           : Chapter 06
Chapter #0.6: start 2487.276444, end 3097.302533
Metadata:
  title           : Chapter 07
Chapter #0.7: start 3097.302533, end 3503.958778
Metadata:
  title           : Chapter 08
Chapter #0.8: start 3503.958778, end 4060.347956
Metadata:
  title           : Chapter 09
Chapter #0.9: start 4060.347956, end 4582.202622
Metadata:
  title           : Chapter 10
Chapter #0.10: start 4582.202622, end 5083.078000
Metadata:
  title           : Chapter 11
Chapter #0.11: start 5083.078000, end 5537.698822
Metadata:
  title           : Chapter 12
Chapter #0.12: start 5537.698822, end 5826.612444
Metadata:
  title           : Chapter 13
Chapter #0.13: start 5826.612444, end 6553.088200
Metadata:
  title           : Chapter 14
Chapter #0.14: start 6553.088200, end 6903.730156
Metadata:
  title           : Chapter 15
Chapter #0.15: start 6903.730156, end 7271.055444
Metadata:
  title           : Chapter 16
Chapter #0.16: start 7271.055444, end 7582.241333
Metadata:
  title           : Chapter 17
Chapter #0.17: start 7582.241333, end 8153.937444
Metadata:
  title           : Chapter 18
Chapter #0.18: start 8153.937444, end 8154.208000
Metadata:
  title           : Chapter 19
Stream #0:0(eng): Video: h264 (High), yuv420p, 1920x800 [SAR 1:1 DAR 12:5], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc (default)
Metadata:
  title           : Change This Metadata
Stream #0:1(eng): Audio: ac3, 48000 Hz, 5.1(side), fltp, 448 kb/s (default)
Metadata:
  title           : Eng
Stream #0:2(eng): Subtitle: subrip (default)
Metadata:
  title           : Eng