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• FFMPEG Cutting Commercials puts audio out of sync

  11 September 2014, by JaBbA

  Ubuntu 14.04.1 with the real ffmpeg loaded (same problem with the avconv version).

  I’m trying to take files created in MythTV with a HDPVR, cut the commercials and put the video into an MP4 container for use with MythRoku.

  the command

  ffmpeg -i $file -acodec copy -vcodec copy -f mp4 file.mp4

  Works fine. Once I update the database, I can watch the file in MythRoku or Plex.

  However, when I try to cut out the commercials, the audio gets out of sync by just over 1 second (audio delayed) whenever I cut past the 0 mark. Totem Video player and VLC both play the resulting video fine, but I can see a "hitch" at the beginning while they are syncing the audio, so I know the information on the audio sync is in the file somewhere. Mythroku and Plex both are out of sync when playing the file. The MythTV Frontend player actually does play it correctly, and I can hear the "hitch" as it syncs the audio.

  After hours of reading posts and playing with settings, I’ve got it down to this:

  If I say:

  ffmpeg -i $file -acodec copy -vcodec copy -f mp4 -ss 0 -t <anything> out.mp4</anything>

  The file is fine, plays both locally and in MythRoku/Plex

  But if I advance the start any amount - even 1 second - audio is out of sync

  ffmpeg -i $file -acodec copy -vcodec copy -f mp4 -ss 1 -t <anything> out.mp4</anything>

  I’ve tried splitting the video (as mp4) and audio (as ac3) first, splitting them separately, and then putting them back together as the last step, but I get the same results.

  The information is in the file - Totem, VLC and the Frontend all can figure it out. How can I get ffmpeg to figure out the sync and write the file so it’s correct?

  Original file:

  mythtv@marvin:~$ mediainfo /var/lib/mythtv/recordings/2225_20140824001500.mpg
  
  General
  
  ID                                       : 0 (0x0)
  
  Complete name                            :     /var/lib/mythtv/recordings/2225_20140824001500.mpg
  
  Format                                   : MPEG-TS
  
  File size                                : 4.03 GiB
  
  Duration                                 : 1h 45mn
  
  Overall bit rate mode                    : Variable
  
  Overall bit rate                         : 5 491 Kbps
  
  
  
  Video
  
  ID                                       : 4113 (0x1011)
  
  Menu ID                                  : 1 (0x1)
  
  Format                                   : AVC
  
  Format/Info                              : Advanced Video Codec
  
  Format profile                           : Main@L4.0
  
  Format settings, CABAC                   : Yes
  
  Format settings, ReFrames                : 4 frames
  
  Format settings, GOP                     : M=4, N=32
  
  Codec ID                                 : 27
  
  Duration                                 : 1h 45mn
  
  Bit rate mode                            : Variable
  
  Bit rate                                 : 4 831 Kbps
  
  Maximum bit rate                         : 20.0 Mbps
  
  Width                                    : 1 280 pixels
  
  Height                                   : 720 pixels
  
  Display aspect ratio                     : 16:9
  
  Frame rate                               : 59.940 fps
  
  Color space                              : YUV
  
  Chroma subsampling                       : 4:2:0
  
  Bit depth                                : 8 bits
  
  Scan type                                : Progressive
  
  Bits/(Pixel*Frame)                       : 0.087
  
  Stream size                              : 3.55 GiB (88%)
  
  Color primaries                          : BT.709
  
  Transfer characteristics                 : BT.709
  
  Matrix coefficients                      : BT.709
  
  
  
  Audio
  
  ID                                       : 4352 (0x1100)
  
  Menu ID                                  : 1 (0x1)
  
  Format                                   : AC-3
  
  Format/Info                              : Audio Coding 3
  
  Mode extension                           : CM (complete main)
  
  Format settings, Endianness              : Big
  
  Codec ID                                 : 129
  
  Duration                                 : 1h 45mn
  
  Bit rate mode                            : Constant
  
  Bit rate                                 : 384 Kbps
  
  Channel(s)                               : 2 channels
  
  Channel positions                        : Front: L R
  
  Sampling rate                            : 48.0 KHz
  
  Bit depth                                : 16 bits
  
  Compression mode                         : Lossy
  
  Delay relative to video                  : -6ms
  
  Stream size                              : 289 MiB (7%)

  File cut from 0:

  mythtv@marvin:~$ mediainfo 2225_20140824001500_1.mp4
  
  General
  
  Complete name                            : 2225_20140824001500_1.mp4
  
  Format                                   : MPEG-4
  
  Format profile                           : Base Media
  
  Codec ID                                 : isom
  
  File size                                : 58.5 MiB
  
  Duration                                 : 1mn 45s
  
  Overall bit rate mode                    : Variable
  
  Overall bit rate                         : 4 676 Kbps
  
  Writing application                      : Lavf54.63.104
  
  
  
  Video
  
  ID                                       : 1
  
  Format                                   : AVC
  
  Format/Info                              : Advanced Video Codec
  
  Format profile                           : Main@L4.0
  
  Format settings, CABAC                   : Yes
  
  Format settings, ReFrames                : 4 frames
  
  Format settings, GOP                     : M=4, N=32
  
  Codec ID                                 : avc1
  
  Codec ID/Info                            : Advanced Video Coding
  
  Duration                                 : 1mn 45s
  
  Bit rate mode                            : Variable
  
  Bit rate                                 : 4 281 Kbps
  
  Maximum bit rate                         : 20.0 Mbps
  
  Width                                    : 1 280 pixels
  
  Height                                   : 720 pixels
  
  Display aspect ratio                     : 16:9
  
  Frame rate mode                          : Variable
  
  Frame rate                               : 59.940 fps
  
  Minimum frame rate                       : 59.920 fps
  
  Maximum frame rate                       : 59.960 fps
  
  Color space                              : YUV
  
  Chroma subsampling                       : 4:2:0
  
  Bit depth                                : 8 bits
  
  Scan type                                : Progressive
  
  Bits/(Pixel*Frame)                       : 0.077
  
  Stream size                              : 53.6 MiB (92%)
  
  Color primaries                          : BT.709
  
  Transfer characteristics                 : BT.709
  
  Matrix coefficients                      : BT.709
  
  
  
  Audio
  
  ID                                       : 2
  
  Format                                   : AC-3
  
  Format/Info                              : Audio Coding 3
  
  Mode extension                           : CM (complete main)
  
  Format settings, Endianness              : Big
  
  Codec ID                                 : ac-3
  
  Duration                                 : 1mn 45s
  
  Bit rate mode                            : Constant
  
  Bit rate                                 : 384 Kbps
  
  Channel(s)                               : 2 channels
  
  Channel positions                        : Front: L R
  
  Sampling rate                            : 48.0 KHz
  
  Bit depth                                : 16 bits
  
  Compression mode                         : Lossy
  
  Stream size                              : 4.81 MiB (8%)

  File cut from 1 second with audio sync problem:

  mythtv@marvin:~$ mediainfo 2225_20140824001500_2.mp4
  
  General
  
  Complete name                            : 2225_20140824001500_2.mp4
  
  Format                                   : MPEG-4
  
  Format profile                           : Base Media
  
  Codec ID                                 : isom
  
  File size                                : 68.0 MiB
  
  Duration                                 : 2mn 0s
  
  Overall bit rate mode                    : Variable
  
  Overall bit rate                         : 4 750 Kbps
  
  Writing application                      : Lavf54.63.104
  
  
  
  Video
  
  ID                                       : 1
  
  Format                                   : AVC
  
  Format/Info                              : Advanced Video Codec
  
  Format profile                           : Main@L4.0
  
  Format settings, CABAC                   : Yes
  
  Format settings, ReFrames                : 4 frames
  
  Format settings, GOP                     : M=4, N=32
  
  Codec ID                                 : avc1
  
  Codec ID/Info                            : Advanced Video Coding
  
  Duration                                 : 1mn 58s
  
  Bit rate mode                            : Variable
  
  Bit rate                                 : 4 394 Kbps
  
  Maximum bit rate                         : 20.0 Mbps
  
  Width                                    : 1 280 pixels
  
  Height                                   : 720 pixels
  
  Display aspect ratio                     : 16:9
  
  Frame rate mode                          : Variable
  
  Frame rate                               : 59.940 fps
  
  Minimum frame rate                       : 59.920 fps
  
  Maximum frame rate                       : 59.960 fps
  
  Color space                              : YUV
  
  Chroma subsampling                       : 4:2:0
  
  Bit depth                                : 8 bits
  
  Scan type                                : Progressive
  
  Bits/(Pixel*Frame)                       : 0.080
  
  Stream size                              : 62.3 MiB (92%)
  
  Color primaries                          : BT.709
  
  Transfer characteristics                 : BT.709
  
  Matrix coefficients                      : BT.709
  
  
  
  Audio
  
  ID                                       : 2
  
  Format                                   : AC-3
  
  Format/Info                              : Audio Coding 3
  
  Mode extension                           : CM (complete main)
  
  Format settings, Endianness              : Big
  
  Codec ID                                 : ac-3
  
  Duration                                 : 2mn 0s
  
  Bit rate mode                            : Constant
  
  Bit rate                                 : 384 Kbps
  
  Channel(s)                               : 2 channels
  
  Channel positions                        : Front: L R
  
  Sampling rate                            : 48.0 KHz
  
  Bit depth                                : 16 bits
  
  Compression mode                         : Lossy
  
  Stream size                              : 5.49 MiB (8%)

• How to reencode flash stream to MP4 or/and WebM inside server implementation?

  18 April 2013, by user2294505

  Hi guys, lets start with this that I'm totally new in video streaming.

  Currently I have to support one server implemented in C that work as mediator between stream producers and stream consumers. In my case I have one remote machine that generate flash stream and one or more clients that can watch it. The server work as proxy for all of them. We are using our server side implementation for rtmp protocol and for asynchronous work over HTTP we are using libevent library. All this construction work fine in common case.

  Now we need to transfer this stream to HTML5 clients and we need to support new formats. Our decision was that MP4 and WebM are enough for us. Base of the HTTP request our internal implementation recognized what type of stream client need. For example when the client need MP4 URI is something like this:

  http://192.168.0.5/video.mp4?blah-blah-blah

  where "blah-blah-blah" are few parameters to impersonate client. We have already implemented mechanism that convert input frames to raw pictures and this implementation work fine when we stream JPEGs as again we are using libavformat library to encode raw picture to JPEG. In case with JPEGs the contents of the stream data must contain HTTP meta data with description of every picture. The client stream request is same as this for MP4 stream but instead video.mp4 we are uising jpegstream.htm

  Now I need to convert this input stream to MP4 and/or WebM and here start my problems. For generating Mp4 and WebM videos I'm using ffmpeg libraries and base of one of ffmpeg examples (muxing) I'm trying to convert already generated pictures to currently selected new format. More or less this conversion is OK but after than I don't know why I can't send video to consumer. I'm using next code to prepare avio context:

  int iSize = 4 * 1024;
  
  unsigned char *ptrBuf = ( unsigned char * )av_malloc( iSize );
  
  ptrOFC->pb = avio_alloc_context( ptrBuf, iSize, 1, ptrTCDObj, NULL, write_pkg, NULL );
  
  if ( !ptrTCDObj->ptrOFC->pb ) {
  
      goto ERROR;
  
  }
  
  avformat_write_header( ptrOFC, NULL );

  When the server receive frame from flash we are converting it to corresponding output format with code like this:

  iResult = avcodec_encode_video2( ptrTCDataObj->m_ptrOCC, &packet, pictureFrame, &iGotPacket );

  and write it to stream when succeed and packet exist with:

  av_interleaved_write_frame( ptrOFC, &packet );

  Here our code expect to receive in one moment call to write_pkg function. But nothing happen here :-(. Situation is 100% same if I'm using direct write with av_write_frame. The write_pkg function has very simple body:

  int write_pkg( void *ptrOpaque, uint8_t *ptrBuffer, int iBufferSize ) 
  
  {
  
      STransCoderData_t *ptrTCDObj = ( STransCoderData_t * ) ptrOpaque;
  
      struct evbuffer *ptrFrameOut;
  
      ptrFrameOut = evbuffer_new();
  
      evbuffer_add( ptrFrameOut, ptrBuffer,( size_t ) iBufferSize );
  
      http_client_write_video( ptrFrameOut, ptrTCDObj->m_ptrHTTPClient, NULL );
  
      evbuffer_free( ptrFrameOut );
  
      return iBufferSize;
  
  }

  Structure STransCoderData_t and function http_client_write_video is not interesting in this moment because we don't reach them for now :-(

  For test consumer I'm using VLC player as open network stream :

  http://192.168.0.5/video.mp4?blah-blah-blah

  VLC don't show anything even errors.

  Any ideas, comments and help are welcome.

• Ffmpeg set duration using node-fluent-ffmpeg

  23 May 2013, by Vprnl

  I'm really new to the world of ffmpeg so please excuses me if this is a stupid queston.

  I'm using the module Node-fluent-ffmpeg to stream a movie and convert it from avi to webm.
  So far so good (it plays the video), but I'm having trouble parsing the duration to the player. My ultimate goal is to be able to skip ahead in the movie. But first the player needs to know how long the video is.

  my code is as followed:

  var stat = fs.statSync(movie);
  
  
  
  var start = 0;
  
  var end = 0;
  
  var range = req.header('Range');
  
  if (range != null) {
  
  start = parseInt(range.slice(range.indexOf('bytes=')+6,
  
    range.indexOf('-')));
  
  end = parseInt(range.slice(range.indexOf('-')+1,
  
    range.length));
  
  }
  
  if (isNaN(end) || end == 0) end = stat.size-1;
  
  if (start > end) return;
  
  
  
  res.writeHead(206, { // NOTE: a partial http response
  
      'Connection':'close',
  
      'Content-Type':'video/webm',
  
      'Content-Length':end - start,
  
      'Content-Range':'bytes '+start+'-'+end+'/'+stat.size,
  
      'Transfer-Encoding':'chunked'
  
  });
  
  
  
  var  proc = new ffmpeg({ source: movie, nolog: true, priority: 1, timeout:15000})
  
      .toFormat('webm')
  
      .withVideoBitrate('1024k')
  
      .addOptions(['-probesize 900000', '-analyzeduration 0', '-bufsize 14000'])
  
      .writeToStream(res, function(retcode, error){
  
      if (!error){
  
          console.log('file has been converted succesfully',retcode);
  
      }else{
  
          console.log('file conversion error',error);
  
      }
  
  });

  I tried to set the header with a start and a end based on this article: http://delog.wordpress.com/2011/04/25/stream-webm-file-to-chrome-using-node-js/

  I also looked in the FFmpeg documentation and found -f duration and -ss.
  But I don't quite know how to convert the byte range to seconds.

  I feel like I'm pretty close to a solution but my inexperience with the subject matter prohibits me from getting it to work. If I'm unclear in any way please let me know. (I have a tendency of explaining things fuzzy.)

  Thanks in advance!