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• libavformat : get formats Mime Type in C++

  9 août 2017, par ZeroTek

  I work on an C++ Application running on Arch Linux that should use libavformat to obtain a media files mime type. Currently using the following lines :

  std::string path = "/path/to/file.extension";
  
  
  
  av_register_all();
  
  AVFormatContext* pFormatCtx = avformat_alloc_context();
  
  avformat_open_input(&pFormatCtx, path.c_str(), NULL, NULL);
  
  avformat_find_stream_info(pFormatCtx, NULL);
  
  
  
  std::string mimeType(pFormatCtx->iformat->mime_type);

  Now, that will work as expected with *.mkv (Matroska) files. Returning the expected Comma seperated mimeType String "video/x-matroska,...". But with any other File Format like *.mp4 or *.avi the iformat->mime_type will always return NULL.

  How do i get the Mime Types of the other Container Formats ?

• C# Problem Reading Console Output to string

  25 septembre 2012, par MoreThanChaos

  i want to launch ffmpeg from my app and retrive all console output that ffmpeg produces. Thing seems obvious, i followed many forum threads/articles like this one but i have problem, though i follow all information included there I seem to end up in dead end.

  String that should contain output from ffmpeg is always empty. I've tried to see where is the problem so i made simple c# console application that only lists all execution parameters that are passed to ffmpeg, just to check if problem is caused by ffmpeg itself. In that case everything work as expected.

  I also did preview console window of my app. When i launch ffmpeg i see all the output in console but the function that should recieve that output for further processing reports that string was empty. When my param-listing app is launched the only thing I see is the expected report from function that gets output.

  So my question is what to do to get ffmpeg output as i intended at first place.

  Thanks in advance
  MTH

• getting a lot of errors when reading udp stream with avconv

  5 août 2015, par eladm26

  I’m trying to read a udp video stream and I’m getting mostly errors :)
  here is my input and output :

  avconv   -i udp://**.**.**.**:**** output.ts
  
  avconv version 11.4, Copyright (c) 2000-2014 the Libav developers
  
    built on Jul 14 2015 12:43:36 with gcc 4.8 (Ubuntu 4.8.4-2ubuntu1~14.04)
  
  [mpeg2video @ 0x25a7060] Invalid frame dimensions 0x0.
  
      Last message repeated 13 times
  
  [mpegts @ 0x2582040] Estimating duration from bitrate, this may be inaccurate
  
  Input #0, mpegts, from 'udp://239.1.1.1:59001':
  
    Duration: N/A, start: 17336.030511, bitrate: 24640 kb/s
  
    Program 3
  
      Stream #0.0[0x31]: Video: mpeg2video (Main), yuv420p, 1920x1080 [PAR 1:1 DAR 16:9], 24000 kb/s, 29.97 fps, 90k tbn, 59.94 tbc
  
      Stream #0.1[0x34](eng): Audio: ac3, 48000 Hz, 5.1, fltp, 448 kb/s
  
      Stream #0.2[0x35](spa): Audio: ac3, 48000 Hz, stereo, fltp, 192 kb/s
  
  File 'output.ts' already exists. Overwrite ? [y/N] y
  
  Output #0, mpegts, to 'output.ts':
  
    Metadata:
  
      encoder         : Lavf56.1.0
  
      Stream #0.0: Video: mpeg2video, yuv420p, 1920x1080 [PAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.97 fps, 90k tbn, 29.97 tbc
  
      Metadata:
  
        encoder         : Lavc56.1.0 mpeg2video
  
      Stream #0.1(eng): Audio: mp2, 48000 Hz, stereo, s16, 384 kb/s
  
      Metadata:
  
        encoder         : Lavc56.1.0 mp2
  
  Stream mapping:
  
    Stream #0:0 -> #0:0 (mpeg2video (native) -> mpeg2video (native))
  
    Stream #0:1 -> #0:1 (ac3 (native) -> mp2 (native))
  
  Press ctrl-c to stop encoding
  
  [mpeg2video @ 0x25c85e0] warning: first frame is no keyframe
  
  Continuity check failed for pid 49 expected 12 got 5 bitrate=3922.8kbits/s
  
  [mpegts @ 0x2582040] Continuity check failed for pid 52 expected 6 got 1
  
  [mpegts @ 0x2582040] Continuity check failed for pid 53 expected 7 got 14
  
  [mpegts @ 0x2582040] Continuity check failed for pid 0 expected 4 got 1
  
  [mpeg2video @ 0x25c85e0] ac-tex damaged at 2 53
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 19 38
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 18 54
  
  [mpeg2video @ 0x25c85e0] ac-tex damaged at 1 39
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 48 55
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 2 56
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 17 40
  
  [mpeg2video @ 0x25c85e0] ac-tex damaged at 5 60
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 1 61
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 16 41
  
  [mpeg2video @ 0x25c85e0] ac-tex damaged at 15 46
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 6 62
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 24 42
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 16 47
  
  [mpeg2video @ 0x25c85e0] mb incr damaged
  
  [mpeg2video @ 0x25c85e0] ac-tex damaged at 3 44
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 8 63
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 11 65
  
  [mpeg2video @ 0x25c85e0] ac-tex damaged at 1 66
  
  [mpeg2video @ 0x25c85e0] invalid mb type in P Frame at 42 50
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 9 51
  
  [mpeg2video @ 0x25c85e0] ac-tex damaged at 45 67
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 48 52
  
  [mpeg2video @ 0x25c85e0] MVs not available, ER not possible.
  
  [mpegts @ 0x2582040] PES packet size mismatch
  
      Last message repeated 1 times
  
  [ac3 @ 0x25c8b00] exponent out-of-range
  
  [ac3 @ 0x25c8b00] error decoding the audio block
  
  [mpegts @ 0x2582040] Continuity check failed for pid 49 expected 13 got 5
  
  [mpegts @ 0x2582040] Continuity check failed for pid 52 expected 12 got 14
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 97 65
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 1 4
  
  [mpeg2video @ 0x25c85e0] invalid cbp at 18 5
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 1 6
  
  [mpeg2video @ 0x25c85e0] mb incr damaged
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 34 8
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 8 9
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 6 11
  
  [mpeg2video @ 0x25c85e0] invalid cbp at 5 18
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 13 19
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 3 20
  
  [mpeg2video @ 0x25c85e0] 00 motion_type at 16 21
  
  [mpeg2video @ 0x25c85e0] invalid cbp at 3 22
  
  [mpeg2video @ 0x25c85e0] invalid mb type in B Frame at 4 23
  
  [mpeg2video @ 0x25c85e0] invalid mb type in B Frame at 3 24

  I’ve searched stack overflow and couldn’t find any similar.
  maybe it has something to do with avconv cant handle the udp frames fast enough ?
  I lost any hope so any help is very welcomed.

  Thanks.