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• "Non-monotonous DTS" and jerky video when copying streams

  2 décembre 2017, par forthrin

  I’m switching containers from MKV to mp4 for a set of video files. This has worked for all videos before, but now I’m getting weird problems (also when converting from MKV to another MKV !)

  1. I’m getting a million Non-monotonous DTS in output stream messages
  2. With QuickTime on macOS the video is jerking back and forth very fast while playing
  3. With VLC on macOS, the video is skipping a lot of frames

  How can I fix this, without re-encoding the video stream ? (Re-encoding audio would be acceptable.) Somehow it must be possible since the original MKV works perfectly !

  $ ffmpeg -i in.mkv -codec copy out.mp4
  
  ffmpeg version 3.3.4 Copyright (c) 2000-2017 the FFmpeg developers
  
    built with Apple LLVM version 9.0.0 (clang-900.0.37)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/3.3.4 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-ffplay --enable-libass --enable-libmp3lame --enable-libx264 --enable-libx265 --enable-libxvid --enable-opencl --enable-videotoolbox --disable-lzma --enable-vda
  
    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
  
    libavresample   3.  5.  0 /  3.  5.  0
  
    libswscale      4.  6.100 /  4.  6.100
  
    libswresample   2.  7.100 /  2.  7.100
  
    libpostproc    54.  5.100 / 54.  5.100
  
  Input #0, matroska,webm, from 'in.mkv':
  
    Metadata:
  
      ENCODER         : Lavf54.63.104
  
    Duration: 00:37:59.98, start: 0.200000, bitrate: 2536 kb/s
  
      Stream #0:0: Video: h264 (High), yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], 23.98 fps, 23.98 tbr, 1k tbn, 47.95 tbc
  
      Stream #0:1(eng): Audio: ac3, 48000 Hz, 5.1(side), fltp, 384 kb/s (default)
  
  [mp4 @ 0x7f93c9006c00] track 1: codec frame size is not set
  
  Output #0, mp4, to 'out.mp4':
  
    Metadata:
  
      encoder         : Lavf57.71.100
  
      Stream #0:0: Video: h264 (High) ([33][0][0][0] / 0x0021), yuv420p(progressive), 1280x720 [SAR 1:1 DAR 16:9], q=2-31, 23.98 fps, 23.98 tbr, 16k tbn, 1k tbc
  
      Stream #0:1(eng): Audio: ac3 ([165][0][0][0] / 0x00A5), 48000 Hz, 5.1(side), fltp, 384 kb/s (default)
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (copy)
  
    Stream #0:1 -> #0:1 (copy)
  
  Press [q] to stop, [?] for help
  
  [mp4 @ 0x7f93c9006c00] Non-monotonous DTS in output stream 0:0; previous: 60720, current: 60064; changing to 60721. This may result in incorrect timestamps in the output file.
  
  [mp4 @ 0x7f93c9006c00] Non-monotonous DTS in output stream 0:0; previous: 63392, current: 62736; changing to 63393. This may result in incorrect timestamps in the output file.
  
  (...repeats a million times...)

  MP4Box :

  $ MP4Box -add in.mkv out.mp4
  
  [MPEG-2 TS] TS Packet 1 is scrambled - not supported
  
  [MPEG-2 TS] TS Packet 3 does not start with sync marker
  
  ...
  
  [MPEG-2 TS] TS Packet 999 does not start with sync marker
  
  [Importer] Unknown input file type
  
  Error importing in.mkv: Corrupted Data in file/stream

  So the file is maybe corrupt ? (Though it plays perfectly to begin with, in VLC at least !) Is there any way I can repair it and convert it to an mp4 file, again without re-encoding the video stream ?

• ffmpeg lose frames when extracting them

  11 octobre 2019, par Francisco Isoardi Prieto

  When I extract all frames from a video, FFmpeg lose one frame. I tried multiple options, like adding more parameters to the function, but none of them worked.

  ffmpeg -i Multicam420-30a.mp4 -framerate 30 frame%08d.jpg

  ffmpeg version N-94077-g01d8c72b95 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 9.1.1 (GCC) 20190621
  configuration : —enable-gpl —enable-version3 —enable-sdl2 —enable-fontconfig —enable-gnutls —enable-iconv —enable-libass —enable-libdav1d —enable-libbluray —enable-libfreetype —enable-libmp3lame —enable-libopencore-amrnb —enable-libopencore-amrwb —enable-libopenjpeg —enable-libopus —enable-libshine —enable-libsnappy —enable-libsoxr —enable-libtheora —enable-libtwolame —enable-libvpx —enable-libwavpack —enable-libwebp —enable-libx264 —enable-libx265 —enable-libxml2 —enable-libzimg —enable-lzma —enable-zlib —enable-gmp —enable-libvidstab —enable-libvorbis —enable-libvo-amrwbenc —enable-libmysofa —enable-libspeex —enable-libxvid —enable-libaom —enable-libmfx —enable-amf —enable-ffnvcodec —enable-cuvid —enable-d3d11va —enable-nvenc —enable-nvdec —enable-dxva2 —enable-avisynth —enable-libopenmpt
  libavutil 56. 29.100 / 56. 29.100
  libavcodec 58. 53.100 / 58. 53.100
  libavformat 58. 28.100 / 58. 28.100
  libavdevice 58. 7.100 / 58. 7.100
  libavfilter 7. 55.100 / 7. 55.100
  libswscale 5. 4.101 / 5. 4.101
  libswresample 3. 4.100 / 3. 4.100
  libpostproc 55. 4.100 / 55. 4.100
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0000023af91f9e80] st : 0 edit list : 1 Missing key frame while searching for timestamp : 0
  [mov,mp4,m4a,3gp,3g2,mj2 @ 0000023af91f9e80] st : 0 edit list 1 Cannot find an index entry before timestamp : 0.
  Input #0, mov,mp4,m4a,3gp,3g2,mj2, from ’Multicam420-30a.mp4’ :
  Metadata :
  major_brand : isom
  minor_version : 512
  compatible_brands : mp41mp42
  creation_time : 2019-08-20T01:30:57.000000Z
  Duration : 00:00:01.00, start : 0.000000, bitrate : 11208 kb/s
  Stream #0:0(eng) : Video : h264 (High) (avc1 / 0x31637661), yuv420p(tv, bt709), 1920x1080 [SAR 1:1 DAR 16:9], 11007 kb/s, 30 fps, 30 tbr, 30k tbn, 60 tbc (default)
  Metadata :
  creation_time : 2019-08-20T01:30:57.000000Z
  encoder : AVC Coding
  Stream #0:1(eng) : Audio : aac (LC) (mp4a / 0x6134706D), 48000 Hz, stereo, fltp, 192 kb/s (default)
  Metadata :
  creation_time : 2019-08-20T01:30:57.000000Z
  Stream mapping :
  Stream #0:0 -> #0:0 (h264 (native) -> mjpeg (native))
  Press [q] to stop, [?] for help
  [swscaler @ 0000023afb923740] deprecated pixel format used, make sure you did set range correctly
  Output #0, image2, to ’frame%08d.jpg’ :
  Metadata :
  major_brand : isom
  minor_version : 512
  compatible_brands : mp41mp42
  encoder : Lavf58.28.100
  Stream #0:0(eng) : Video : mjpeg, yuvj420p(pc), 1920x1080 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 30 fps, 30 tbn, 30 tbc (default)
  Metadata :
  creation_time : 2019-08-20T01:30:57.000000Z
  encoder : Lavc58.53.100 mjpeg
  Side data :
  cpb : bitrate max/min/avg : 0/0/200000 buffer size : 0 vbv_delay : -1
  frame= 29 fps= 17 q=24.8 Lsize=N/A time=00:00:00.96 bitrate=N/A speed=0.557x
  video:3153kB audio:0kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead : unknown

  As you can see, the original video has 30 frames and last 1 second, and the output frames are 29 and less than a second.

• ffmpeg creating mpeg-dash chunk files too slowly resulting in 404 errors

  17 juillet 2021, par Danny

  I have a hardware encoder feeding FFmpeg to create a MPEG-DASH Low Latency stream. It works well for a while, but after letting FFmpeg run for a while and reloading the page there are many 404 errors.

  


  When that happens, the dash.js player tries to fetch the segment file on the "live edge" but the file has not been created yet by FFmpeg. For example, after running for 20-30 minutes and loading the web page player, debug code in the web server shows :

  


  2021-07-16 16:46:30.64 : GET REQUEST : /data/ott/chunk-stream0-00702.m4s
2021-07-16 16:46:30.67 : NOT FOUND. Latest files on filesystem:
    chunk-stream0-00699.m4s.tmp
    chunk-stream0-00698.m4s
    chunk-stream0-00697.m4s
    chunk-stream0-00696.m4s
    ...


  


  So you can see the browser requested chunk 702 but the latest on the server is (part of) 699. With 2 second chunks, that is 3-5 seconds of content not yet available.

  


  To analyze, I modified FFmpeg's dashenc.c to add a timestamp every time a file is opened which displays like :

  


  [dash @ 0x9b17c0] 21:48:52.935 1626443332.935  : dashenc_io_open() - opened /data/ott/chunk-stream0-00060.m4s.tmp


  


  And loaded the timestamps into Excel.

  


  Despite a segment duration of 2.000 seconds, the average time between file opens is 2.011 seconds. Over two hours this accumulated to a 45 second difference between the calculated live edge and the latest file on the server.

  


  The HW encoder is set to 25 fps and a GOP size of 5. I've confirmed both by analyzing the H.264 NALUs output by the HW encoder.

  


  My Question : Is this a bug in FFmpeg or can I avoid this problem by adjusting the settings of either the HW encoder and/or FFmpeg options ?

  


  REFERENCE

  


  FFmpeg: Version 4.4 
Centos 8 
Apache 2.4.37


  


  FFmpeg command line (pipe is fed by process reading HW encoder)

  


  ffmpeg -re -loglevel verbose -an -f h264 -i pipe:17 -c:v copy \
-f dash -dash_segment_type mp4 -b:v 1000000 -seg_duration 2.000000 \
-frag_type duration -frag_duration 0.200000 -target_latency 1 \
-window_size 10 -extra_window_size 5 -remove_at_exit 1 -streaming 1 \
-ldash 1 -use_template 1 -use_timeline 0 -write_prft 1 -avioflags direct \
-fflags +nobuffer+flush_packets -format_options movflags=+cmaf \
-utc_timing_url /web/be/time.php /data/ott/master.mpd


  


  Modified dash_io_open() from dashenc.c

  


  static int 
dashenc_io_open(AVFormatContext *s, AVIOContext **pb, char *filename, AVDictionary **options)
{
    DASHContext *c = s->priv_data;
    int http_base_proto = filename ? ff_is_http_proto(filename) : 0;
    int err = AVERROR_MUXER_NOT_FOUND;
    if (!*pb || !http_base_proto || !c->http_persistent)
    {
        err = s->io_open(s, pb, filename, AVIO_FLAG_WRITE, options);

        // My Debug
        {
            char buf[20], milli[60];
            struct timeb tp;

            ftime(&tp); // sec + ms
            struct tm *tmInfo = localtime(&tp.time);

            // 2020-05-15 21:15:12.123
            strftime(buf, sizeof(buf), "%H:%M:%S", tmInfo);
            snprintf(milli, 59, "%s.%03d %d.%03d ", buf, tp.millitm, tp.time, tp.millitm);

            av_log(s, AV_LOG_INFO, "%s : dashenc_io_open() - opened %s\n", milli, filename);
        }
    }
    return err;
}