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• ffmpeg - MXF with 4-channel audio : how to create proxies (high quality / small file size) and preserve the audio mapping

  8 juillet 2018, par WhatsYourFunction

  We’ve got MXF sources (h.264 video at UHD (3840x2160) with 4-channels of (4 - PCM S24 mono sources)
  We want Proxies — smallest file size at highest picture quality
  The compression applied to the video and audio essences can be anything,
  And the wrapper can be either MXF or QuickTime
  but we need to preserve the audio mapping (i.e. the Proxy must be 4-channel audio)

  How to do that with ffmpeg ?

  • EDIT Adding ffprobe :

  Metadata :

  uid : ***

  generation_uid : ***

  company_name : CANON

  product_name : EOS C300 Mark II

  product_version : 1.00

  product_uid : ***

  modification_date : 2018-06-28T08:29:24.000000Z

  material_package_umid : ***

  timecode : 02:50:31:17

  Duration : 00:06:35.40, start : 0.000000, bitrate : 395842 kb/s

  Stream #0:0 : Video : h264 (High 4:2:2 Intra), yuv422p10le(tv, progressive), 3840x2160, SAR 1:1 DAR 16:9, 23.98 fps, 23.98 tbr, 23.98 tbn, 47.95 tbc

  Metadata :

   file_package_umid: ***

  Stream #0:1 : Audio : pcm_s24le, 48000 Hz, 1 channels, s32 (24 bit), 1152 kb/s

  Metadata :

   file_package_umid: ***

  Stream #0:2 : Audio : pcm_s24le, 48000 Hz, 1 channels, s32 (24 bit), 1152 kb/s

  Metadata :

   file_package_umid: ***

  Stream #0:3 : Audio : pcm_s24le, 48000 Hz, 1 channels, s32 (24 bit), 1152 kb/s

  Metadata :

   file_package_umid: ***

  Stream #0:4 : Audio : pcm_s24le, 48000 Hz, 1 channels, s32 (24 bit), 1152 kb/s

  Metadata :

   file_package_umid: ***

• ffmpeg with high delay in first input stream

  15 juin 2018, par DeStOv

  My goal is to use ffmpeg to create a stream which contains two other streams (both input streams should be next to each other). In general it works with the following command :

  ffmpeg -i rtmp://server/live/streamA -i rtmp://server/live/streamB \
  
      -filter_complex '[0:v]pad=800:ih+10[int];[int][1:v]overlay=400:0[vid]' \
  
      -map [vid] -f flv - | ffplay -fflags nobuffer -

  The problem is that streamA has a quite large delay of two to three seconds, i.e. if something happens in streamA it is shown after 2 seconds. The delay for streamB is moderate.

  If I swap the order of the input streams, i.e. "-i .../streamB -i .../streamA" streamB has the high delay and the delay of streamA is moderate. My guess is that this is because the second stream is opened some seconds after the first stream was opened (but I don’t know for sure).

  How can i fix it so that both streamA and streamB are in real time ?

• Decoding a h264 (High) stream with OpenCV's ffmpeg on Ubuntu

  5 juin 2018, par arvids

  I am working with a video stream from an ip camera on Ubuntu 14.04. Everything was going great with a camera that has these parameters (from FFMPEG) :

      Stream #0:0: Video: h264 (Main), yuv420p(progressive), 352x192, 29.97 tbr, 90k tbn, 180k tbc

  But then i changed to a newer camera, which has these parameters :

      Stream #0:0: Video: h264 (High), yuvj420p(pc, bt709, progressive), 1280x720, 25 fps, 25 tbr, 90k tbn, 50 tbc

  My C++ program uses OpenCV3 to process the stream. By default OpenCV uses ffmpeg to decode and display the stream with function VideoCapture.

  VideoCapture vc;
  
  vc.open(input_stream);
  
  while ((vc >> frame), !frame.empty()) {
  
     *do work*
  
  }

  With the new camera stream i get errors like these (from ffmpeg) :

  [h264 @ 0x7c6980] cabac decode of qscale diff failed at 41 38
  
  [h264 @ 0x7c6980] error while decoding MB 41 38, bytestream (3572)
  
  [h264 @ 0x7c6980] left block unavailable for requested intra mode at 0 44
  
  [h264 @ 0x7bc2c0] SEI type 25 truncated at 208

  The image sometimes is glitched, sometimes completely frozen. However on vlc it plays perfectly. I installed the newest version (3.2.2) of ffmpeg player with

  ./configure --enable-gpl --enable-libx264

  Now playing directly with ffplay (instead of launching from source code with OpenCV function VideoCapture), the stream plays better, but sometimes still displays warnings :

  [NULL @ 0x7f834c008c00] SEI type 25 size 896 truncated at 320=1/1   
  
  [h264 @ 0x7f834c0d5d20] SEI type 25 size 896 truncated at 319=1/1   
  
  [rtsp @ 0x7f834c0008c0] max delay reached. need to consume packet   
  
  [rtsp @ 0x7f834c0008c0] RTP: missed 1 packets
  
  [h264 @ 0x7f834c094740] concealing 675 DC, 675 AC, 675 MV errors in P frame

  Changing the camera hardware is not an option. The camera can be set to encode to h265 or mjpeg. When encoding to mjpeg it can output 5 fps, which is not enough. Decoding to a static video is not an option either, because i need to display real time results about the stream. Here is a list of API backends that can be used in function VideoCapture. Maybe i should switch to some other decoder and player ?
  From my research i conclude that i have these options :

  • Somehow get OpenCV to use libVlc instead of ffmpeg

  One example of switching to vlc is here, but i don’t understand it well enough to say if that is what i need. Or maybe i should be parsing the stream in code ?

  • Use vlc to preprocess the stream, as suggested here.

  This is probably slow, which again is bad for real time results.
  Any suggestions and coments will be appreciated.