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• Revision 697a8e6fe6 : Avoid setting rate multiplier as 0 In high bitdepth setting, the rate multipier

  24 août 2015, par hui su

  Changed Paths :
   Modify /vp10/encoder/rd.c

  
   Modify /vp9/encoder/vp9_rd.c

  
  
  Avoid setting rate multiplier as 0

  In high bitdepth setting, the rate multipier may be set as 0. In
  lossless mode, the RD cost would always be 0, resulting in bad
  partition and prediction mode choices.

  Change-Id : I297014dd8bfa8a07ff0ab480119f75678300ff68

• Taking a high resolution picture with FFMPEG and Webcam

  13 mai 2016, par user2088176

  I have a Microsoft LifeCam VX-3000 and I want to capture a single image from this video source.

  I have tried DirectShow :

  ffmpeg -f dshow -video_size 1280x960 -i video="Microsoft LifeCam VX-3000" -vframes 1 file.jpg
  
  
  
  [dshow @ 01D69340] Could not set video options

  and
  Microsoft WDM Image Capture :

  ffmpeg -f vfwcap -video_size 1280x960 -i video="Microsoft LifeCam VX-3000" -vframes 1 file.jpg
  
  
  
  [vfwcap @ 01D79340] Could not set Video Format.

  If I lower the video size to 640x480, it works, but every sites tells me that 640x480 is the maximum video resolution, but the still picture maximum resolution is 1280x960. Like here

  I would like to capture the image at the highest resolution possible. Is there a way to do it with FFMPEG ? What command-line options should I give it ?

  Thank you very much.

• 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.