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  • FFmpeg skipping time after concat

    19 septembre 2017, par Manul Hüttinger

    I am trying to concatenate videos and in my resulting Videos I have the issue that at the concat edges my video is skipping/glitching.

    General Workflow

    in general my workflow looks like this

    1. Stream via ffmpeg
    2. capture stream and segment all 2 mins in to TS files
    3. concat TS file to MP4 video
    4. cut MP4 video at the desired Timestamps

    Detailed Look at Step 4

    as I am handling 2-hours+ videos I don’t want to re-encode the whole video. So I am looking for the closest I Frames to my In and Outpoint and cut 1 Frame before/after. As my result I get 3 Videos (front/middle/back). Now it is only needed to re-encode front and back and concat all three Videos.
    So far the theory

    General Observations

    As I look at my resulting video, I obeservated the following.
    frontpart duration is e.g. 3.2 secs. I skip framewise through the Video and get nice and clean timestamps ( 00:00:02.620, 00:00:02:660 )
    As soon as I get to my cutting edge the timestamps are skipping some frames and changing (00:00:03.200, 00:00:03.408 ,00:00:03.409). When I look only at the single frame images, their are no missing/dropped frames

    when I concat my TS files, the results contains a messed up frame rate e.g from constant 25 F/s to 25.0096 F/s

    FFMPEG instructions

    FRONT Video

    ffmpeg -ss 232.52 -i src.mp4 -t 3.24 -filter_complex "setpts=PTS-STARTPTS" -vcodec libx264 -profile:v baseline -level 31 -bf 0  -f mp4 -y front.mp4
    
ffmpeg version n3.3 Copyright (c) 2000-2017 the FFmpeg developers
    
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
    
  configuration: --prefix=/usr --extra-cflags=-I/usr/include --extra-ldflags=-L/usr/lib --bindir=/usr/local/bin --extra-libs=-ldl --enable-gpl --enable-libass --enable-libfdk-aac --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree --enable-libssh --enable-openssl
    
  libavutil      55. 58.100 / 55. 58.100
    
  libavcodec     57. 89.100 / 57. 89.100
    
  libavformat    57. 71.100 / 57. 71.100
    
  libavdevice    57.  6.100 / 57.  6.100
    
  libavfilter     6. 82.100 /  6. 82.100
    
  libswscale      4.  6.100 /  4.  6.100
    
  libswresample   2.  7.100 /  2.  7.100
    
  libpostproc    54.  5.100 / 54.  5.100
    
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'src.mp4':
    
  Metadata:
    
    major_brand     : isom
    
    minor_version   : 512
    
    compatible_brands: isomiso2avc1mp41
    
    encoder         : Lavf55.33.100
    
  Duration: 01:06:00.33, start: 0.000000, bitrate: 610 kb/s
    
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 1280x464 [SAR 1:1 DAR 80:29], 537 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc (default)
    
    Metadata:
    
      handler_name    : VideoHandler
    
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 65 kb/s (default)
    
    Metadata:
    
      handler_name    : SoundHandler
    
Stream mapping:
    
  Stream #0:0 (h264) -> setpts (graph 0)
    
  setpts (graph 0) -> Stream #0:0 (libx264)
    
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
    
Press [q] to stop, [?] for help
    
[libx264 @ 0x31ea160] using SAR=1/1
    
[libx264 @ 0x31ea160] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX LZCNT
    
[libx264 @ 0x31ea160] profile Constrained Baseline, level 3.1
    
[libx264 @ 0x31ea160] 264 - core 148 - H.264/MPEG-4 AVC codec - Copyleft 2003-2016 - http://www.videolan.org/x264.html - options: cabac=0 ref=3 deblock=1:0:0 analyse=0x1:0x111 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=3 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
    
Output #0, mp4, to 'front.mp4':
    
  Metadata:
    
    major_brand     : isom
    
    minor_version   : 512
    
    compatible_brands: isomiso2avc1mp41
    
    encoder         : Lavf57.71.100
    
    Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1280x464 [SAR 1:1 DAR 80:29], q=-1--1, 25 fps, 12800 tbn, 25 tbc (default)
    
    Metadata:
    
      encoder         : Lavc57.89.100 libx264
    
    Side data:
    
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
    
    Stream #0:1(und): Audio: aac (LC) ([64][0][0][0] / 0x0040), 44100 Hz, mono, fltp, 69 kb/s (default)
    
    Metadata:
    
      handler_name    : SoundHandler
    
      encoder         : Lavc57.89.100 aac
    
frame=   81 fps= 31 q=-1.0 Lsize=     151kB time=00:00:03.25 bitrate= 379.5kbits/s speed=1.23x
    
video:119kB audio:28kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 2.531915%
    
[libx264 @ 0x31ea160] frame I:1     Avg QP:17.43  size: 38268
    
[libx264 @ 0x31ea160] frame P:80    Avg QP:21.05  size:  1038
    
[libx264 @ 0x31ea160] mb I  I16..4: 71.4%  0.0% 28.6%
    
[libx264 @ 0x31ea160] mb P  I16..4:  0.2%  0.0%  0.0%  P16..4:  7.8%  1.8%  0.6%  0.0%  0.0%    skip:89.6%
    
[libx264 @ 0x31ea160] coded y,uvDC,uvAC intra: 21.8% 40.8% 23.1% inter: 1.6% 4.2% 0.2%
    
[libx264 @ 0x31ea160] i16 v,h,dc,p: 66% 25%  5%  4%
    
[libx264 @ 0x31ea160] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 30% 28% 15%  4%  4%  5%  4%  5%  4%
    
[libx264 @ 0x31ea160] i8c dc,h,v,p: 51% 24% 21%  4%
    
[libx264 @ 0x31ea160] ref P L0: 74.3% 15.2% 10.5%
    
[libx264 @ 0x31ea160] kb/s:299.56
    
[aac @ 0x31edfa0] Qavg: 123.323

    MIDDLE Video

    ffmpeg -ss 235.88 -i src.mp4 -c copy -t 1492.96 -f mp4 -y middle.mp4 
    
ffmpeg version n3.3 Copyright (c) 2000-2017 the FFmpeg developers
    
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
    
  configuration: --prefix=/usr --extra-cflags=-I/usr/include --extra-ldflags=-L/usr/lib --bindir=/usr/local/bin --extra-libs=-ldl --enable-gpl --enable-libass --enable-libfdk-aac --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree --enable-libssh --enable-openssl
    
  libavutil      55. 58.100 / 55. 58.100
    
  libavcodec     57. 89.100 / 57. 89.100
    
  libavformat    57. 71.100 / 57. 71.100
    
  libavdevice    57.  6.100 / 57.  6.100
    
  libavfilter     6. 82.100 /  6. 82.100
    
  libswscale      4.  6.100 /  4.  6.100
    
  libswresample   2.  7.100 /  2.  7.100
    
  libpostproc    54.  5.100 / 54.  5.100
    
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'src.mp4':
    
  Metadata:
    
    major_brand     : isom
    
    minor_version   : 512
    
    compatible_brands: isomiso2avc1mp41
    
    encoder         : Lavf55.33.100
    
  Duration: 01:06:00.33, start: 0.000000, bitrate: 610 kb/s
    
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 1280x464 [SAR 1:1 DAR 80:29], 537 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc (default)
    
    Metadata:
    
      handler_name    : VideoHandler
    
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 65 kb/s (default)
    
    Metadata:
    
      handler_name    : SoundHandler
    
Output #0, mp4, to 'middle.mp4':
    
  Metadata:
    
    major_brand     : isom
    
    minor_version   : 512
    
    compatible_brands: isomiso2avc1mp41
    
    encoder         : Lavf57.71.100
    
    Stream #0:0(und): Video: h264 (Main) ([33][0][0][0] / 0x0021), yuv420p, 1280x464 [SAR 1:1 DAR 80:29], q=2-31, 537 kb/s, 25 fps, 25 tbr, 90k tbn, 90k tbc (default)
    
    Metadata:
    
      handler_name    : VideoHandler
    
    Stream #0:1(und): Audio: aac (LC) ([64][0][0][0] / 0x0040), 44100 Hz, mono, fltp, 65 kb/s (default)
    
    Metadata:
    
      handler_name    : SoundHandler
    
Stream mapping:
    
  Stream #0:0 -> #0:0 (copy)
    
  Stream #0:1 -> #0:1 (copy)
    
Press [q] to stop, [?] for help
    
frame=37329 fps=16333 q=-1.0 Lsize=  113774kB time=00:24:52.95 bitrate= 624.3kbits/s speed= 653x
    
video:100359kB audio:12095kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.173957%

    BACK Video

    ffmpeg -ss 1728.88 -i 'src.mp4' -t 3.9199999999998 -filter_complex "setpts=PTS-STARTPTS" -vcodec libx264 -profile:v baseline -level 31 -bf 0  -f mp4 -y back.mp4
    
ffmpeg version n3.3 Copyright (c) 2000-2017 the FFmpeg developers
    
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
    
  configuration: --prefix=/usr --extra-cflags=-I/usr/include --extra-ldflags=-L/usr/lib --bindir=/usr/local/bin --extra-libs=-ldl --enable-gpl --enable-libass --enable-libfdk-aac --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree --enable-libssh --enable-openssl
    
  libavutil      55. 58.100 / 55. 58.100
    
  libavcodec     57. 89.100 / 57. 89.100
    
  libavformat    57. 71.100 / 57. 71.100
    
  libavdevice    57.  6.100 / 57.  6.100
    
  libavfilter     6. 82.100 /  6. 82.100
    
  libswscale      4.  6.100 /  4.  6.100
    
  libswresample   2.  7.100 /  2.  7.100
    
  libpostproc    54.  5.100 / 54.  5.100
    
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'src.mp4':
    
  Metadata:
    
    major_brand     : isom
    
    minor_version   : 512
    
    compatible_brands: isomiso2avc1mp41
    
    encoder         : Lavf55.33.100
    
  Duration: 01:06:00.33, start: 0.000000, bitrate: 610 kb/s
    
    Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p, 1280x464 [SAR 1:1 DAR 80:29], 537 kb/s, 25 fps, 25 tbr, 90k tbn, 50 tbc (default)
    
    Metadata:
    
      handler_name    : VideoHandler
    
    Stream #0:1(und): Audio: aac (LC) (mp4a / 0x6134706D), 44100 Hz, mono, fltp, 65 kb/s (default)
    
    Metadata:
    
      handler_name    : SoundHandler
    
Stream mapping:
    
  Stream #0:0 (h264) -> setpts (graph 0)
    
  setpts (graph 0) -> Stream #0:0 (libx264)
    
  Stream #0:1 -> #0:1 (aac (native) -> aac (native))
    
Press [q] to stop, [?] for help
    
[libx264 @ 0x2672160] using SAR=1/1
    
[libx264 @ 0x2672160] using cpu capabilities: MMX2 SSE2Fast SSSE3 SSE4.2 AVX LZCNT
    
[libx264 @ 0x2672160] profile Constrained Baseline, level 3.1
    
[libx264 @ 0x2672160] 264 - core 148 - H.264/MPEG-4 AVC codec - Copyleft 2003-2016 - http://www.videolan.org/x264.html - options: cabac=0 ref=3 deblock=1:0:0 analyse=0x1:0x111 me=hex subme=7 psy=1 psy_rd=1.00:0.00 mixed_ref=1 me_range=16 chroma_me=1 trellis=1 8x8dct=0 cqm=0 deadzone=21,11 fast_pskip=1 chroma_qp_offset=-2 threads=3 lookahead_threads=1 sliced_threads=0 nr=0 decimate=1 interlaced=0 bluray_compat=0 constrained_intra=0 bframes=0 weightp=0 keyint=250 keyint_min=25 scenecut=40 intra_refresh=0 rc_lookahead=40 rc=crf mbtree=1 crf=23.0 qcomp=0.60 qpmin=0 qpmax=69 qpstep=4 ip_ratio=1.40 aq=1:1.00
    
Output #0, mp4, to 'back.mp4':
    
  Metadata:
    
    major_brand     : isom
    
    minor_version   : 512
    
    compatible_brands: isomiso2avc1mp41
    
    encoder         : Lavf57.71.100
    
    Stream #0:0: Video: h264 (libx264) ([33][0][0][0] / 0x0021), yuv420p, 1280x464 [SAR 1:1 DAR 80:29], q=-1--1, 25 fps, 12800 tbn, 25 tbc (default)
    
    Metadata:
    
      encoder         : Lavc57.89.100 libx264
    
    Side data:
    
      cpb: bitrate max/min/avg: 0/0/0 buffer size: 0 vbv_delay: -1
    
    Stream #0:1(und): Audio: aac (LC) ([64][0][0][0] / 0x0040), 44100 Hz, mono, fltp, 69 kb/s (default)
    
    Metadata:
    
      handler_name    : SoundHandler
    
      encoder         : Lavc57.89.100 aac
    
frame=   98 fps= 27 q=-1.0 Lsize=     268kB time=00:00:03.92 bitrate= 559.2kbits/s speed=1.07x
    
video:230kB audio:33kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.538479%
    
[libx264 @ 0x2672160] frame I:1     Avg QP:19.57  size:112129
    
[libx264 @ 0x2672160] frame P:97    Avg QP:21.68  size:  1270
    
[libx264 @ 0x2672160] mb I  I16..4: 35.4%  0.0% 64.6%
    
[libx264 @ 0x2672160] mb P  I16..4:  0.2%  0.0%  0.1%  P16..4:  6.9%  2.0%  0.8%  0.0%  0.0%    skip:90.1%
    
[libx264 @ 0x2672160] coded y,uvDC,uvAC intra: 54.4% 69.1% 54.2% inter: 2.0% 3.6% 0.3%
    
[libx264 @ 0x2672160] i16 v,h,dc,p: 63% 23%  8%  6%
    
[libx264 @ 0x2672160] i4 v,h,dc,ddl,ddr,vr,hd,vl,hu: 26% 17% 11%  6%  8%  9%  7%  8%  8%
    
[libx264 @ 0x2672160] i8c dc,h,v,p: 50% 18% 24%  7%
    
[libx264 @ 0x2672160] ref P L0: 81.8% 11.5%  6.7%
    
[libx264 @ 0x2672160] kb/s:480.15
    
[aac @ 0x2675fa0] Qavg: 119.994

    CONCAT Videos

    ffmpeg -f concat -safe 0 -i concat.txt -c copy -r 25 -y /concat.mp4 
    
ffmpeg version n3.3 Copyright (c) 2000-2017 the FFmpeg developers
    
  built with gcc 5.4.0 (Ubuntu 5.4.0-6ubuntu1~16.04.4) 20160609
    
  configuration: --prefix=/usr --extra-cflags=-I/usr/include --extra-ldflags=-L/usr/lib --bindir=/usr/local/bin --extra-libs=-ldl --enable-gpl --enable-libass --enable-libfdk-aac --enable-libmp3lame --enable-libopus --enable-libtheora --enable-libvorbis --enable-libvpx --enable-libx264 --enable-nonfree --enable-libssh --enable-openssl
    
  libavutil      55. 58.100 / 55. 58.100
    
  libavcodec     57. 89.100 / 57. 89.100
    
  libavformat    57. 71.100 / 57. 71.100
    
  libavdevice    57.  6.100 / 57.  6.100
    
  libavfilter     6. 82.100 /  6. 82.100
    
  libswscale      4.  6.100 /  4.  6.100
    
  libswresample   2.  7.100 /  2.  7.100
    
  libpostproc    54.  5.100 / 54.  5.100
    
Input #0, concat, from 'concat.txt':
    
  Duration: N/A, start: 0.000000, bitrate: N/A
    
    Stream #0:0: Video: h264 (Constrained Baseline) ([27][0][0][0] / 0x001B), yuv420p(progressive), 1280x464 [SAR 1:1 DAR 80:29], 25 fps, 25 tbr, 90k tbn, 50 tbc
    
    Stream #0:1(und): Audio: aac (LC) ([15][0][0][0] / 0x000F), 44100 Hz, mono, fltp, 74 kb/s
    
Output #0, mp4, to 'concat.mp4':
    
  Metadata:
    
    encoder         : Lavf57.71.100
    
    Stream #0:0: Video: h264 (Constrained Baseline) ([33][0][0][0] / 0x0021), yuv420p(progressive), 1280x464 [SAR 1:1 DAR 80:29], q=2-31, 25 fps, 25 tbr, 12800 tbn, 25 tbc
    
    Stream #0:1(und): Audio: aac (LC) ([64][0][0][0] / 0x0040), 44100 Hz, mono, fltp, 74 kb/s
    
Stream mapping:
    
  Stream #0:0 -> #0:0 (copy)
    
  Stream #0:1 -> #0:1 (copy)
    
Press [q] to stop, [?] for help
    
frame=37508 fps=7256 q=-1.0 Lsize=  114285kB time=00:25:00.59 bitrate= 623.9kbits/s speed= 290x
    
video:100672kB audio:12598kB subtitle:0kB other streams:0kB global headers:1kB muxing overhead: 0.896435%

    If needed I can provide samples.

  • Dreamcast Serial Extractor

    31 décembre 2017, par Multimedia Mike — Sega Dreamcast

    It has not been a very productive year for blogging. But I started the year by describing an unfinished project that I developed for the Sega Dreamcast, so I may as well end the year the same way. The previous project was a media player. That initiative actually met with some amount of success and could have developed into something interesting if I had kept at it.

    By contrast, this post describes an effort that was ultimately a fool’s errand that I spent way too much time trying to make work.

    Problem Statement
    In my neverending quest to analyze the structure of video games while also hoarding a massive collection of them (though I’m proud to report that I did play at least a few of them this past year), I wanted to be able to extract the data from my many Dreamcast titles, both games and demo discs. I had a tool called the DC Coder’s Cable, a serial cable that enables communication between a Dreamcast and a PC. With the right software, you could dump an entire Dreamcast GD-ROM, which contained a gigabyte worth of sectors.

    Problem : The dumping software (named ‘dreamrip’ and written by noted game hacker BERO) operated in a very basic mode, methodically dumping sector after sector and sending it down the serial cable. This meant that it took about 28 hours to extract all the data on a single disc by running at the maximum speed of 115,200 bits/second, or about 11 kilobytes/second. I wanted to create a faster method.

    The Pitch
    I formed a mental model of dreamrip’s operation that looked like this :



    As an improvement, I envisioned this beautiful architecture :



    Architectural Assumptions
    My proposed architecture was predicated on the assumption that the disc reading and serial output functions were both I/O-bound operations and that the CPU would be idle much of the time. My big idea was to use that presumably idle CPU time to compress the sectors before sending them over the wire. As long as the CPU can compress the data faster than 11 kbytes/sec, it should be a win. In order to achieve this, I broke the main program into 3 threads :

    1. The first thread reads the sectors ; more specifically, it asks the drive firmware to please read the sectors and make the data available in system RAM
    2. The second thread waits for sector data to appear in memory and then compresses it
    3. The third thread takes the compressed data when it is ready and shuffles it out through the serial cable

    Simple and elegant, right ?

    For data track compression, I wanted to start with zlib in order to prove the architecture, but then also try bzip2 or lzma. As long as they could compress data faster than the serial port could write it, then it should be a win. For audio track compression, I wanted to use the Flake FLAC encoder. According to my notes, I did get both bzip2 compression and the Flake compressor working on the Dreamcast. I recall choosing Flake over the official FLAC encoder because it was much simpler and had fewer dependencies, always an important consideration for platforms such as this.

    Problems
    I worked for quite awhile on this project. I have a lot of notes recorded but a lot of the problems I had remain a bit vague in my memory. However, there was one problem I discovered that eventually sunk the entire initiative :

    The serial output operation is CPU-bound.

    My initial mental model was that the a buffer could be “handed off” to the serial subsystem and the CPU could go back to doing other work. Nope. Turns out that the CPU was participating at every step of the serial transfer.

    Further, I eventually dug into the serial driver code and learned that there was already some compression taking place via the miniLZO library.

    Lessons Learned

    • Recognize the assumptions that you’re making up front at the start of the project.
    • Prototype in order to ensure plausibility
    • Profile to make sure you’re optimizing the right thing (this is something I have learned again and again).

    Another interesting tidbit from my notes : it doesn’t matter how many sectors you read at a time, the overall speed is roughly the same. I endeavored to read 1000 2048-byte data sectors, 1 or 10 or 100 at a time, or all 1000 at once. My results :

    • 1 : 19442 ms
    • 10 : 19207 ms
    • 100 : 19194 ms
    • 1000 : 19320 ms

    No difference. That surprised me.

    Side Benefits
    At one point, I needed to understand how BERO’s dreamrip software was operating. I knew I used to have the source code but I could no longer find it. Instead, I decided to try to reverse engineer what I needed from the SH-4 binary image that I had. It wasn’t an ELF image ; rather, it was a raw binary meant to be loaded at a particular memory location which makes it extra challenging for ‘objdump’. This led to me asking my most viewed and upvoted question on Stack Overflow : “Disassembling A Flat Binary File Using objdump”. The next day, it also led me to post one of my most upvoted answers when I found the solution elsewhere.

    Strangely, I have since tried out the command line shown in my answer and have been unable to make it work. But people keep upvoting both the question and the answer.

    Eventually this all became moot when I discovered a misplaced copy of the source code on one of my computers.

    I strongly recall binging through the Alias TV show while I was slogging away on this project, so I guess that’s a positive association since I got so many fun screenshots out of it.

    The Final Resolution
    Strangely, I was still determined to make this project work even though the Dreamcast SD adapter arrived for me about halfway through the effort. Part of this was just stubbornness, but part of it was my assumptions about serial port speeds, in particular, my assumption that there was a certain speed-of-light type of limitation on serial port speeds so that the SD adapter, operating over the DC’s serial port, would not be appreciably faster than the serial cable.

    This turned out to be very incorrect. In fact, the SD adapter is capable of extracting an entire gigabyte disc image in 35-40 minutes. This is the method I have since been using to extract Dreamcast disc images.

    The post Dreamcast Serial Extractor first appeared on Breaking Eggs And Making Omelettes.

  • matroskadec : export cover art correctly

    3 avril 2015, par wm4
    matroskadec : export cover art correctly

    Generally, libavformat exports cover art pictures as video streams with
    
1 packet and AV_DISPOSITION_ATTACHED_PIC set. Only matroskadec exported
    
it as attachment with codec_id set to AV_CODEC_ID_MJPEG.
    

    Obviously, this should be consistent, so change the Matroska demuxer to
    
export a AV_DISPOSITION_ATTACHED_PIC pseudo video stream.
    

    Matroska muxing is probably incorrect too. I know that it can create
    
broken files with an audio track and just 1 video frame when e.g.
    
remuxing mp3 with APIC to mkv. But for now this commit does not change
    
anything about muxing, and also continues to write attachments with
    
AV_CODEC_ID_MJPEG should the muxer application have special knowledge
    
that the Matroska is broken in this way.
    

    Signed-off-by : Anton Khirnov <anton@khirnov.net>
    • [DBH] libavformat/matroska.c
    • [DBH] libavformat/matroska.h
    • [DBH] libavformat/matroskadec.c
    • [DBH] libavformat/matroskaenc.c

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