Recherche avancée

Sur d’autres sites (17004)

• 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.

• Gstreamer playing audio from video file with (uri)decodebin - high CPU usage

  28 mai 2017, par Alexey Elesin

  I’m using gstreamer to convert audio from files/RTMP/RTSP streams and then analyze it.

  The problem is, if my source file is video or videostream gstreamer uses a lot of CPU.

  Example 1 (video) - uses 30-35% of CPU as htop says.

  gst-launch-1.0 uridecodebin uri='test.mp4' ! autoaudiosink

  Example 2 (audio from video file above converted with ffmpeg -c copy) - uses 2-4% of CPU

  gst-launch-1.0 uridecodebin uri='test.mp3' ! autoaudiosink

  How can I specify that I only need audio source from the video file ?

  I’m using decodebin because I don’t know which files (formats) I will get from users.

• avfilter/vf_cover_rect : Handle the case where the cover rectangle is as large as...

  12 mai 2015, par Michael Niedermayer

  avfilter/vf_cover_rect : Handle the case where the cover rectangle is as large as the input
  Fixes division by 0
  
  Fixes CID1297575
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavfilter/vf_cover_rect.c