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• Adding chapters to MP4 files, and being identified on iOS 12 podcast app

  5 avril 2019, par Craig Francis

  I have an MP4 file, where I’ve added chapters via ffmpeg.

  But in the iOS 12 Podcasts app, from Apple, the chapters don’t appear. This should happen, as noted by idownloadblog.com

  

  In comparison, when using QuickLook on MacOS, the list of chapters can be seen by clicking the chapters button (in the bottom right hand side of the window).

  

  And opening in QuickTime Player, while there isn’t a list of chapters to view, you can use the "View > Next Chapter" menu item.

  So I’m assuming this is a bug in iOS... but I’m wondering if there is another way to add chapters ? or if I’ve made a mistake ?

  ---

  My current process is to create a "ffmetadata" file, as noted in the ffmpeg documentation :

  ;FFMETADATA1
  
  title=Example
  
  
  
  [CHAPTER]
  
  TIMEBASE=1/1000
  
  START=0
  
  END=221913
  
  title=Chapter 1
  
  
  
  [CHAPTER]
  
  TIMEBASE=1/1000
  
  START=221913
  
  END=1169241
  
  title=Chapter 2

  https://ffmpeg.org/ffmpeg-formats.html#Metadata-1

  Then I’ve tried each of the following commands :

  ffmpeg -i 2019-01-02.mp4 -i 2019-01-02.meta -map_metadata 1 -codec copy 2019-01-02-chapters.mp4
  
  ffmpeg -i 2019-01-02.mp4 -i 2019-01-02.meta -map_metadata 1 2019-01-02-chapters.mp4
  
  ffmpeg -i 2019-01-02.mp4 -i 2019-01-02.meta -map_metadata 1 2019-01-02-chapters.mp3

  • The first one is from the ffmpeg documentation, where -codec copy means the audio file is not re-encoded.
  • The second one takes longer, while it re-encodes the audio data.
  • The third one requires re-encoding to convert it into an MP3 file (which uses ID3 tags for the chapter data).

  ---

  On a slightly unrelated note, the third party app "RSSRadio" does list the chapters, but the feature added in version 4 that allows you to "skip directly to the start of the next chapter", if the next chapter starts within the next 3 minutes, does not seem to work.

• Problems transcoding GoToMeeting output using FFmpeg

  20 avril 2014, par user3466413

  I’m having a nightmare of a time transcoding output from GoToMeeting, recorded using the latest OS X version, to something web-playable. No matter what settings I use, I end up with time syncing problems, at least with this particular recording.

  The .mov file looks like this. Note that it’s variable framerate, and because it’s mostly just a screencast of a PowerPoint presentation with occasional mouse movement, the output should be VFR too to produce a small file yet still preserve occasional motion.

  $ ffmpeg -i original.mov
  
  ffmpeg version N-58273-g18df75f Copyright (c) 2000-2013 the FFmpeg developers
  
    built on Nov 19 2013 10:34:42 with Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
  
    configuration: --enable-gpl --enable-version3 --enable-nonfree --enable-postproc --enable-libass --enable-libcelt --enable-libfaac --enable-libfdk-aac --enable-libfreetype --enable-libmp3lame --enable-libopencore-amrnb --enable-libopencore-amrwb --enable-libopenjpeg --enable-openssl --enable-libopus --enable-libschroedinger --enable-libspeex --enable-libtheora --enable-libvo-aacenc --enable-libvorbis --enable-libvpx --enable-libx264 --enable-libxvid --prefix=/usr/local
  
    libavutil      52. 53.100 / 52. 53.100
  
    libavcodec     55. 43.101 / 55. 43.101
  
    libavformat    55. 21.100 / 55. 21.100
  
    libavdevice    55.  5.100 / 55.  5.100
  
    libavfilter     3. 91.100 /  3. 91.100
  
    libswscale      2.  5.101 /  2.  5.101
  
    libswresample   0. 17.104 /  0. 17.104
  
    libpostproc    52.  3.100 / 52.  3.100
  
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0x7f822980a000] decoding for stream 0 failed
  
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'original.mov':
  
    Metadata:
  
      major_brand     : qt
  
      minor_version   : 537199360
  
      compatible_brands: qt
  
      creation_time   : 2014-03-20 02:09:22
  
    Duration: 03:08:26.72, start: 0.000000, bitrate: 75 kb/s
  
      Stream #0:0(und): Video: h264 (Main) (avc1 / 0x31637661), yuv420p(tv), 1368x728 [SAR 1:1 DAR 171:91], 20 kb/s, 0.60 fps, 600 tbr, 600 tbn, 1200 tbc (default)
  
      Metadata:
  
        creation_time   : 2014-03-20 02:09:22
  
        handler_name    : Apple Alias Data Handler
  
      Stream #0:1(eng): Audio: aac (mp4a / 0x6134706D), 16000 Hz, mono, fltp, 47 kb/s (default)
  
      Metadata:
  
        creation_time   : 2014-03-20 02:09:22
  
        handler_name    : Apple Alias Data Handler
  
      Stream #0:2(eng): Data: none (rtp  / 0x20707472), 6 kb/s
  
      Metadata:
  
        creation_time   : 2014-03-20 02:09:22
  
        handler_name    : Apple Alias Data Handler
  
      Stream #0:3(und): Data: none (rtp  / 0x20707472), 0 kb/s
  
      Metadata:
  
        creation_time   : 2014-03-20 02:09:22
  
        handler_name    : Apple Alias Data Handler

  The .mov file (which I unfortunately cannot publicly post) plays back properly in any application I use : VLC, Media Player Classic, and QuickTime. However, playing the transcoded output always exhibits the following symptoms :

  • Audio out of sync with what the video is showing, sometimes to the order of minutes off towards the end of this three hour recording
  • In the case of Media Player Classic, clicking a spot on the timeline actually moves the playhead to a spot on the timeline near where I clicked, but not directly on it.

  There are the arguments I’m using for a .mp4 encoding that is playable in all browsers that support H.264. Note that this is on Windows but Linux exhibits the same problems.

  ffmpeg.exe -y -i original.mov -i watermark.png -filter_complex "[0:v] crop=1184:720:178:6,scale=1184:720,setsar=1/1; [0:v][1:v] overlay=1242:648 [0:v]" -vcodec libx264 -acodec libvo_aacenc -q:a 80 -crf 30 -ac 1 -ar 16000 -strict -2 -profile:v baseline -level 3 outout.mkv

  The arguments, other than those that are self-explanatory or trivial :

  • -filter_complex : Crop excess letterboxing/pillarboxing from the video and set the aspect ratio to 1:1 for square pixels (something Safari needed), then overlay a watermark from a PNG and resize the output to 720p
  • -crf 30 : encode the video at constant quality, variable bitrate
  • -ac 1 -ar 16000 : encode with mono audio at 16 KHz
  • -strict -2 -profile:v baseline -level 3 : encode using FFmpeg’s "experimental" H.264 encoder using the Baseline level 3 profile for web compatibility

  Note that yes, this goes to an MKV container initially because, for some reason, encoding directly to a .mp4 container hangs FFmpeg. I then use -acodec copy -vcodec copy to copy the audio and video streams directly into a .mp4 container. Finally I pass the output through MP4Box to interleave it so it can be progressively downloaded.

  When transcoding, FFmpeg does drop frames, which I suspect is related to the problem, with output like this :

  FFmpeg: frame=  232 fps= 26 q=24.0 size=    5983kB time=00:32:44.57 bitrate=  24.9kbits/s dup=0 drop=1487

  When I then later attempt to mux it into the .mp4 container from this temporary .mkv container, I get a flood of warnings like this :

  [mp4 @ 0297cd00] Non-monotonous DTS in output stream 0:0; previous: 6341306, current: 6007024; changing to 6341307. This may result in incorrect timestamps in the output file.

  Now I wouldn’t be surprised if there is indeed some problem with the source file. However, if so, I need to definitively prove just how it’s broken.

  Any thoughts ?

• Segmentation Fault when running ffmpeg+sdl program

  23 juin 2015, par user2270995

  I started with Dranger’s tutorials on building a video player using FFMPEG and SDL. The code tutorial4 compiles fine but when i run it i get a segmentation fault error. here’s the code for tutorial4.

  I am using gcc

  Apple LLVM version 6.1.0 (clang-602.0.49) (based on LLVM 3.6.0svn)
  
  Target: x86_64-apple-darwin14.3.0
  
  Thread model: posix 

  on Mac 10.10.3.

  Here’s GDB Backtrace :

   Program received signal SIGSEGV, Segmentation fault.
  
  [Switching to Thread 0x1813 of process 84136]
  
  0x00007fff955d4432 in stack_not_16_byte_aligned_error ()
  
  from /usr/lib/system/libdyld.dylib
  
  (gdb) backtrace 
  
  #0  0x00007fff955d4432 in stack_not_16_byte_aligned_error ()
  
  from /usr/lib/system/libdyld.dylib
  
  #1  0x000000010a2f1ee0 in ?? ()
  
  #2  0x0000000101341008 in ?? () from /usr/local/lib/libSDL-1.2.0.dylib
  
  #3  0x00000000000005d0 in ?? ()
  
  #4  0x00000001013362e9 in RunThread () from /usr/local/lib/libSDL-1.2.0.dylib
  
  #5  0x00000001013362e2 in RunThread () from /usr/local/lib/libSDL-1.2.0.dylib
  
  #6  0x00007fff8d1d4268 in ?? () from /usr/lib/system/libsystem_pthread.dylib
  
  #7  0x0000000000006f23 in ?? ()
  
  #8  0x000000010a2f2000 in ?? ()
  
  #9  0x000000010a2f1f50 in ?? ()  
  
  #10 0x00007fff8d1d41e5 in ?? () from /usr/lib/system/libsystem_pthread.dylib
  
  #11 0x0000000000000000 in ?? ()
  
  (gdb) 

  Backtrace for another SIGSEGV :

  Program received signal SIGSEGV, Segmentation fault.
  
  [Switching to Thread 0x15eb of process 11453]
  
  0x00000001012c9475 in av_log_format_line ()
  
  from /usr/local/lib/libavutil.54.dylib
  
  (gdb) bt
  
  #0  0x00000001012c9475 in av_log_format_line ()
  
  from /usr/local/lib/libavutil.54.dylib
  
  #1  0x00000001012f7338 in av_pix_fmt_descriptors ()
  
  from /usr/local/lib/libavutil.54.dylib
  
  #2  0x00000018012f7358 in ?? ()
  
  #3  0x000000010a2f3010 in ?? ()
  
  #4  0x000000010a2f2c10 in ?? ()
  
  #5  0x000000010011d65a in ?? () from  /usr/local/lib/libavformat.56.dylib
  
  #6  0x000000010a2f3900 in ?? ()
  
  #7  0x0000000000000018 in ?? ()
  
  #8  0x0000000000000018 in ?? ()
  
  #9  0x000000010011d65a in ?? () from /usr/local/lib/libavformat.56.dylib
  
  #10 0x000000010a2f3900 in ?? ()
  
  #11 0x910016d093cdc267 in ?? ()
  
  #12 0x000000010a2f3eb0 in ?? ()
  
  #13 0x00000001012c96e8 in av_log_default_callback ()
  
  from /usr/local/lib/libavutil.54.dylib
  
  #14 0x0000000000000000 in ?? ()
  
  (gdb) 

  The call to SDL_WaitEvent in main method is where these errors occur in my debugging.

  for(;;) {
  
  SDL_WaitEvent(&event);
  
  switch(event.type) {
  
  case FF_QUIT_EVENT:
  
  case SDL_QUIT:
  
    is->quit = 1;
  
    SDL_Quit();
  
    return 0;
  
    break;
  
  case FF_REFRESH_EVENT:
  
    video_refresh_timer(event.user.data1);
  
    break;
  
  default:
  
    break;
  
   }
  
  }

  is this related to pthread library or sdl And how do i resolve it ?