Recherche avancée

Sur d’autres sites (5820)

• How Can I record a live stream using ffmpeg ? (Without any encoding or transcoding)

  26 février 2015, par Sina Davani

  How Can I record a live stream using ffmpeg ? (Without any encoding or transcoding)

  I have a program written using ffmpeg. It captures a live stream and then plays it on the display (a simple video player).
  What I need now is the ability to save the input stream in a file on the disk so it could be played later using a standard video player.
  Can anyone please give me a simple example that would show how it is done ? When I am writing the captured packets from the input stream directly in to a file ; at the end the file is corrupted and it is unusable. I did try to set the header for the file ; but that didn’t work either.

  The Live stream comes from an IP camera ; so it is already encoded in the H264 format. so I am guessing it should be possible to directly write it in a file without any encoding.

  while (av_read_frame(pFormatCtx, &packet) >= 0)
  
  {
  
      // Is this a packet from the video stream?
  
      if (packet.stream_index == videoStreamID)
  
      {
  
          // Decode video frame
  
          if (avcodec_decode_video2(pCodecCtx, pFrame, &frameFinished, &packet) <= 0) input->sizeOfDroppedPacketStructures += packet.size;
  
  
  
  
  
          partTimeReadSize += packet.size;
  
          ++numberOfPacketsForFrame;
  
  
  
  
  
          // Did we get a video frame?
  
          if (frameFinished)
  
          {           
  
              // Convert the image from its native format to RGB
  
              sws_scale(sws_ctx, (uint8_t const * const *)pFrame->data, pFrame->linesize, 0, pCodecCtx->height, pFrameRGB->data, pFrameRGB->linesize);
  
  
  
              frameNumber = pCodecCtx->frame_number;
  
              Mat cvFrame(pCodecCtx->height, pCodecCtx->width, CV_8UC3, pFrameRGB->data[0], pFrameRGB->linesize[0]);
  
  
  
              //namedWindow(input->URL.c_str(), WINDOW_AUTOSIZE);
  
              imshow(input->URL.c_str(), cvFrame);
  
  
  
  
  
              cvFrame.release();
  
  
  
  
  
  
  
              QueryPerformanceCounter(&now);
  
              double waitTime = (1.0 / av_q2d(pCodecCtx->framerate)) * 1000.0 - ((double)(now.QuadPart - lastTime.QuadPart) / (double)freq.QuadPart) * 1000;              
  
              if (waitTime < 0) waitTime = 0;
  
              Sleep(waitTime);
  
              QueryPerformanceCounter(&lastTime);
  
          }
  
      }
  
  
  
      // Free the packet that was allocated by av_read_frame
  
      av_free_packet(&packet);
  
      SDL_PollEvent(&event);
  
      switch (event.type) {
  
      case SDL_QUIT:
  
          SDL_Quit();
  
          exit(0);
  
          break;
  
      default:
  
          break;
  
      }
  
  }   

• avformat : add fields to AVProgram/AVStream for PMT change tracking

  18 mai 2018, par Aman Gupta

  avformat : add fields to AVProgram/AVStream for PMT change tracking
  These fields will allow the mpegts demuxer to expose details about
  
  the PMT/program which created the AVProgram and its AVStreams.
  In mpegts, a PMT which advertises streams has a version number
  
  which can be incremented at any time. When the version changes,
  
  the pids which correspond to each of it's streams can also change.
  Since ffmpeg creates a new AVStream per pid by default, an API user
  
  needs the ability to (a) detect when the PMT changed, and (b) tell
  
  which AVStream were added to replace earlier streams.
  This has been a long-standing issue with ffmpeg's handling of mpegts
  
  streams with PMT changes, and I found two related patches in the wild
  
  that attempt to solve the same problem :
  The first is in MythTV's ffmpeg fork, where they added a
  
  void (*streams_changed)(void*) ; to AVFormatContext and call it from
  
  their fork of the mpegts demuxer whenever the PMT changes.
  The second was proposed by XBMC in
  
  https://ffmpeg.org/pipermail/ffmpeg-devel/2012-December/135036.html,
  
  where they created a new AVMEDIA_TYPE_DATA stream with id=0 and
  
  attempted to send packets to it whenever the PMT changed.
  Signed-off-by : Aman Gupta <aman@tmm1.net>
  

  • [DH] doc/APIchanges
  • [DH] libavformat/avformat.h
  • [DH] libavformat/utils.c
  • [DH] libavformat/version.h

• swscale/cms : add color management subsystem

  29 novembre 2024, par Niklas Haas

  swscale/cms : add color management subsystem
  The underlying color mapping logic was ported as straightforwardly as possible
  
  from libplacebo, although the API and glue code has been very heavily
  
  refactored / rewritten. In particular, the generalization of gamut mapping
  
  methods is replaced by a single ICC intent selection, and constants have been
  
  hard-coded.
  To minimize the amount of overall operations, this gamut mapping LUT now embeds
  
  a direct end-to-end transformation to the output color space ; something that
  
  libplacebo does in shaders, but which is prohibitively expensive in software.
  In order to preserve compatibility with dynamic tone mapping without severely
  
  regressing performance, we add the ability to generate a pair of "split" LUTS,
  
  one for encoding the input and output to the perceptual color space, and a
  
  third to embed the tone mapping operation. Additionally, this intermediate
  
  space could be used for additional subjective effect (e.g. changing
  
  saturation or brightness).
  The big downside of the new approach is that generating a static color mapping
  
  LUT is now fairly slow, as the chromaticity lobe peaks have to be recomputed
  
  for every single RGB value, since correlated RGB colors are not necessarily
  
  aligned in ICh space. Generating a split 3DLUT significantly alleviates this
  
  problem because the expensive step is done as part of the IPT input LUT, which
  
  can share the same hue peak calculation at least for all input intensities.
  

  • [DH] libswscale/Makefile
  • [DH] libswscale/cms.c
  • [DH] libswscale/cms.h