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• Splitting odd and even frames in Gstreamer

  4 avril 2014, par user3498379

  I am building an application whereby I need to split a videostream(RTSP/MJPEG) into individual frames. The extracted frames then need to be put into two named pipes. I need to alternate the frames between two named pipes, i.e. even frames go to pipe one and odd frames go to pipe 2. I have been able to achieve this with ffmpeg using the following command :

  ffmpeg -i "rtsp://<ipaddress>/axis-media/media.amp?videocodec=jpeg" -vf select="mod(n-1\,2)" -vcodec mjpeg -f avi -y  -vf select="not(mod(n-1\,2))" -vcodec mjpeg -f avi -y 
  
  </ipaddress>

  However I have run into an RTP packet size issue with ffmpeg when using large resolutions e.g. 2048x1536. My question is ; is there a gstreamer equivalent command ? I have the basic gstreamer command which extracts images :

   gst-launch rtspsrc location=rtsp://<ipaddress>/axis-media/media.amp?videocodec=jpeg ! decodebin2 ! jpegenc ! multifilesink location="frame%d.jpg"
  
  </ipaddress>

  But now I need the additional piece, any help will be much appreciated.

• saving H.264 encoded images with libavcodec

  8 octobre 2011, par user846400

  I am getting H.264 images from an IP camera and want to save the encoded images (without decoding). I am using output-example.c from ffmpeg (libavformat/output-example.c) for this purpose. For Saving the raw H.264 image, I do the following :

  AVPacket pkt;
  
  av_init_packet(&pkt);
  
  if (c->coded_frame->pts != AV_NOPTS_VALUE)
  
          pkt.pts= av_rescale_q(c->coded_frame->pts, c->time_base, st->time_base);
  
  if(c->coded_frame->key_frame)
  
          pkt.flags |= PKT_FLAG_KEY;
  
  pkt.stream_index= st->index;
  
  pkt.data= (uint8_t *)ulAddr;//video_outbuf;
  
  pkt.size= out_size;
  
  save_image(pkt.data, out_size);

  Where ulAddr is the address pointer to the image and out_size is the image size. Instead of saving the images to a media video file, I want to save the individual images. save_image function simply uses basic fopen and fwrite functions for saving the images. If I decode the frame and then save, everything works fine. But I have problem saving the encoded frames. The encoded frames are saved with a very small size and then they cannot be decoded.
  Is there anything wrong ? I will really appreciate any help in this regard.

• rtmpproto : Validate the embedded flv packet size before copying

  3 octobre 2013, par Martin Storsjö

  rtmpproto : Validate the embedded flv packet size before copying
  This wasn’t an issue prior to 58404738, when the whole RTMP packet
  
  was copied at once and the length of the individual embedded flv
  
  packets only were validated by the flv demuxer.
  Prior to this patch, this could lead to reads and writes out of bound.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] libavformat/rtmpproto.c