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• How to use FFTools to determine actual FPS of an RTMP stream

  17 mai 2016, par Dexter1759

  I’m trying to determine the best way to analyse any RTMP stream. I’m currently settled upon the FFMPEG suite of tools, however, I find myself in need of help before I drive myself crazy.

  I’m trying to validate a stream, I’ve been asked to determine the following :

  • Can I connect to the stream ? - this can be done easily with FFProbe
  • Is there video ? (i.e. it’s not all black) - I’ve managed to build a POC so don’t think this will be a problem.
  • Is there audio ? (i.e. not all silent) - Again, don’t think this is a problem based on my POC.
  • Actual FPS - here’s where I get stuck because the meta data shows 25fps and that’s what FFTools return.

  However, using FFPlay I can see the odd message of "no frame !" and would prefer to calculate the actual FPS for comparison.

  Any help/advice with this toolset would be useful.

  (Note : I’ve also had other issues/questions with this toolset but have started with this one rather than dump a list here)

  Many thanks.

  EDIT - Forgot to mention the stream is of a live feed so things like "duration" and "nb_frames" return "N/A"

• How to determine the correct format when remuxing streams ?

  1er février 2016, par Nyaruko

  I used ffmpeg(libavcodec) to remuxing a incoming h264 stream. The following is the part where I initialize the output format context :

  int ret;
  
  ffmpeg::AVDictionary *opts2 = NULL;
  
  av_dict_set(&opts2, "preset", "medium", 0);
  
  av_dict_set(&opts2, "crf", "29", 0);
  
  av_dict_set(&opts2, "profile", "baseline", 0);
  
  av_dict_set(&opts2, "level", "30", 0);
  
  av_dict_set(&opts2, "maxrate", "200000", 0);
  
  av_dict_set(&opts2, "minrate", "0", 0);
  
  av_dict_set(&opts2, "bufsize", "2000000", 0);
  
  
  
  ffmpeg::AVOutputFormat* fmt = ffmpeg::av_guess_format("mpeg", NULL, NULL);
  
  // Open the context
  
  //---------------------------------------------------------------------
  
  outFormatCtx = ffmpeg::avformat_alloc_context();
  
  if (!outFormatCtx)
  
  {
  
      return false;
  
  }
  
  
  
  //Set the output format
  
  //----------------------------------------------------------------------
  
  outFormatCtx->oformat = fmt;
  
  
  
  // Open the output file
  
  //-------------------------------------
  
  if (!(outFormatCtx->flags & AVFMT_NOFILE))
  
  {
  
      ret = ffmpeg::avio_open2(&outFormatCtx->pb, "Record.avi", AVIO_FLAG_WRITE, NULL, NULL);
  
      if (ret < 0)
  
      {
  
          return false;
  
      }
  
  }
  
  // Create the output stream
  
  // -------------------------------------
  
  ffmpeg::AVStream* out_stream = ffmpeg::avformat_new_stream(outFormatCtx, inputStream->codec->codec);
  
  if (!out_stream) 
  
  {
  
      return false;
  
  }
  
  
  
  //Set the stream parameters
  
  //-------------------------------------
  
  ret = ffmpeg::avcodec_copy_context(out_stream->codec, inputStream->codec);
  
  if (ret < 0) 
  
  {
  
      return false;
  
  }
  
  
  
  // Check then setup for global headers
  
  //-------------------------------------
  
  if (outFormatCtx->oformat->flags & AVFMT_GLOBALHEADER)
  
      out_stream->codec->flags |= CODEC_FLAG_GLOBAL_HEADER;
  
  
  
  av_dump_format(outFormatCtx, 0, "Record.avi", 1);
  
  
  
  
  
  
  
  //Write the header
  
  //--------------------------------------
  
  ret = ffmpeg::avformat_write_header(outFormatCtx, &opts2);
  
  if (ret < 0) 
  
  {
  
      return false;
  
  }

  Then it says I am not setting the VBV buffer size, and remuxing might fail. And the results actually give black screen.

  How could I choose the correct format instead of guessing it ?
  Or How could I set the VBV buffer size ?

• How to determine webm duration using ffprobe

  19 février 2017, par Lopakhin

  My goal is simple , I have several webm files need to be concated, but first I need to determine their durations.

  It seems webm file are played as streams, so there is no way to tell the length of each file.

  I have been using ffprobe to do the job ,but the duration returned is N/A.The command I use was :

  ffprobe -i input.file -show_format | grep duration

  thanks.

  The complete output of ffprobe list below :

   ffprobe version 2.6.2 Copyright (c) 2007-2015 the FFmpeg developers
  
    built with Apple LLVM version 6.1.0 (clang-602.0.49) (based on LLVM 3.6.0svn)
  
    configuration: --prefix=/usr/local/Cellar/ffmpeg/2.6.2 --enable-shared --enable-pthreads --enable-gpl --enable-version3 --enable-hardcoded-tables --enable-avresample --cc=clang --host-cflags= --host-ldflags= --enable-libx264 --enable-libmp3lame --enable-libvo-aacenc --enable-libxvid --enable-libtheora --enable-libvorbis --enable-libvpx --enable-vda
  
    libavutil      54. 20.100 / 54. 20.100
  
    libavcodec     56. 26.100 / 56. 26.100
  
    libavformat    56. 25.101 / 56. 25.101
  
    libavdevice    56.  4.100 / 56.  4.100
  
    libavfilter     5. 11.102 /  5. 11.102
  
    libavresample   2.  1.  0 /  2.  1.  0
  
    libswscale      3.  1.101 /  3.  1.101
  
    libswresample   1.  1.100 /  1.  1.100
  
    libpostproc    53.  3.100 / 53.  3.100
  
  Input #0, matroska,webm, from '231':
  
    Metadata:
  
      encoder         : GStreamer matroskamux version 1.5.91
  
      creation_time   : 2015-12-05 07:59:29
  
    Duration: N/A, start: 0.000000, bitrate: N/A
  
      Stream #0:0(eng): Video: vp8, yuv420p, 640x480, SAR 1:1 DAR 4:3, 14.99 fps, 14.99 tbr, 1k tbn, 1k tbc (default)
  
      Metadata:
  
        title           : Video
  
      Stream #0:1(eng): Audio: vorbis, 48000 Hz, stereo, fltp (default)
  
      Metadata:
  
        title           : Audio
  
  duration=N/A