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• Decode h264 video with csharp

  28 août 2011, par john bowring

  I am looking for a way to decode h264 (or indeed any video format) using c#. The ultimate goal is to be able to decode the images and very strictly control the playback in real time. The project I am working on is a non-linear video art piece where the HD footage is required to loop and edit itself on the fly, playing back certain frame ranges and then jumping to the next randomly selected frame range seamlessly.

  I have created an app which reads image files (jpegs) in from the disk and plays them on screen in order, I have total control over which frame is laoded and when it is displayed but at full HD res it takes slightly longer than I want to load the images from hard drive (which are about 500k each), I am thinking that using a compressed video format would be smaller and therefore faster to read and decode into a particular frame however I cannot find any readily avaiable way to do this.

  Are there any libraries which can do this ? i.e. extract an arbitrary frame from a video file and serve it to my app in less time than it takes to show the frame (running at 25fps), I have looked into the vlc libraries and wrappers for ffmpeg but I don't know which would be better or if there would be another even better option. Also I dont know which codec would be the best choice as some are keyframe based making arbitrary frame extraction probably very difficult.

  Any advice welcome, thanks

• Play FFMPEG Sound Sample with OpenAL

  16 avril 2013, par Asim

  i am using FFMPEG to load Audio Video from File...with the video its working but i don't know how to play audio samples coming ... here is my routine that is getting audio samples...

  m_AdotimeBase = (int64_t(m_Adocdec_ctx->time_base.num) * AV_TIME_BASE) / int64_t(m_Adocdec_ctx->time_base.den);   
  
  if(!m_Adofmt_ctx)
  
  {
  
      //AfxMessageBox(L"m_timeBase");
  
      return FALSE ;
  
  }
  
  int64_t seekAdoTarget = int64_t(m_currFrame) * m_AdotimeBase;   
  
  
  
  
  
  if(av_seek_frame(m_Adofmt_ctx, -1, seekAdoTarget, AVSEEK_FLAG_ANY) < 0)
  
  {
  
      /*CString st;
  
      st.Format(L"%d",m_currFrame);
  
      AfxMessageBox(L"av_seek_frame "+st);*/
  
      m_currFrame = m_totalFrames-1;
  
      return FALSE ;
  
  }
  
  
  
  if ((ret = av_read_frame(m_Adofmt_ctx, &packet)) < 0)
  
          return FALSE;
  
  if (packet.stream_index == 0)       
  
  {
  
      ret = avcodec_decode_audio4(m_Adocdec_ctx, &in_AdeoFrame, &got_frame, &packet);
  
      if (ret < 0) 
  
      {
  
          av_free_packet(&packet);
  
          return FALSE;
  
      }
  
  }

  My problem is i want to listen that coming sample using OPENAL i tried hard to develop using this but won't be able .... but no success Please help mee. if u have some tutorial or refrence material plz do share with me

• libavformat stuck in ff_network_wait_fd

  3 juin 2020, par Daniel

  I'm using libavformat for remuxing some live video feeds (rtsp).

  



  I can't really create a minimal reproducable example, because the issue is not reproducable, but I have an attached debugger and if I have any minimal chance to examine the root cause I'd not skip any chance.

  



  The stream is opened via avformat_open_input, and there is a custom IO for writing the output (avformat_alloc_output_context2).

  



  The problem is that avformat is stuck in ff_network_wait_fd, at least by gdb :

  



  #0  0xb673e120 in poll () at ../sysdeps/unix/syscall-template.S:84
#1  0x004a3ff4 in ff_network_wait_fd (fd=-1357954584, write=1) at libavformat/network.c:72
#2  0xaf0f428e in ?? ()
Backtrace stopped: previous frame identical to this frame (corrupt stack?)


  



  There was a network failure during the connection or the stream and I have not got any aggressive stream closing mechanism (everything is non blocking, there is no waits, sleeps, everything is event-based by libev).

  



  This just happened once during one month so it's very hard to reproduce but it is still running and gdb is attached.

  



  I'm curious if I have any chance to dig deeper. The stack seems corrupted and also the fd seems invalid for what ff_network_wait_fd waits for.

  



  Also, I never call ff_network_wait_fd directly, but there is an alternative : ff_network_wait_fd_timeout. Is it possible to ask libavformat to use this alternative so it won't block my thread if there is unreliable network ?