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• FFmpeg with Pipe - how can I periodically grab real-time frames out of live streams in C# ?

  2 mars 2020, par BBy

  I am new to FFmpeg and C# and I want grab frames to do image processing with IP Camera.

  I have made the following C# class and I could get a single frame from IP Camera.

  class FFmpegHandler
  
      {
  
          public Process ffmpeg = new Process();
  
          public Image image;
  
  
  
          public Image init()
  
          {
  
              ffmpeg = new Process()
  
              {
  
                  StartInfo =
  
                  {
  
                      FileName = @"./ffmpeg/ffmpeg.exe",
  
                      //Arguments = "-i http://admin:@192.168.10.1/videostream.asf -an -f image2pipe -preset ultrafast -tune zerolatency -s 320x240 pipe:1", // Hangs
  
                      Arguments = "-i http://admin:@192.168.10.1/videostream.asf -vframes 1 -an -f image2pipe -preset ultrafast -tune zerolatency -s 320x240 pipe:1",
  
                      UseShellExecute = false,
  
                      RedirectStandardOutput = true,
  
                      RedirectStandardError = true,
  
                      CreateNoWindow = true,
  
                      WorkingDirectory = "./ffmpeg/"
  
                  }
  
              };
  
  
  
              ffmpeg.EnableRaisingEvents = true;
  
              ffmpeg.Start();
  
  
  
              var stream = ffmpeg.StandardOutput.BaseStream;
  
              var img = Image.FromStream(stream);
  
              //ffmpeg.WaitForExit();
  
  
  
              return img;
  
          }
  
      }   

  The problem is that I want to grab real-time (latest) images when I request.

  If I run FFmpegHandler.init(), it will take 2 seconds to give me delayed image output.

  I have tried removing argument -vframes 1, then it will hang after image = Image.FromStream(stream) ;.

  When I check the ffmpeg output directly, it looks like ffmpeg is keep building the stream

  frame=    6 fps=0.0 q=2.2 size=      25kB time=00:00:00.24 bitrate= 861.9kbits/s dup=4 drop=0 speed=0.435x    
  
  frame=   65 fps= 60 q=24.8 size=     140kB time=00:00:02.60 bitrate= 440.9kbits/s dup=4 drop=0 speed=2.41x    
  
  frame=   77 fps= 49 q=24.8 size=     161kB time=00:00:03.08 bitrate= 428.0kbits/s dup=4 drop=0 speed=1.95x    
  
  frame=   89 fps= 43 q=24.8 size=     182kB time=00:00:03.56 bitrate= 418.6kbits/s dup=4 drop=0 speed= 1.7x    
  
  frame=  102 fps= 39 q=24.8 size=     205kB time=00:00:04.08 bitrate= 410.7kbits/s dup=4 drop=0 speed=1.57x    
  
  frame=  116 fps= 37 q=24.8 size=     229kB time=00:00:04.64 bitrate= 404.2kbits/s dup=4 drop=0 speed=1.49x    
  
  frame=  128 fps= 35 q=24.8 size=     250kB time=00:00:05.12 bitrate= 399.8kbits/s dup=4 drop=0 speed=1.41x    
  
  frame=  142 fps= 34 q=24.8 size=     274kB time=00:00:05.68 bitrate= 395.7kbits/s dup=4 drop=0 speed=1.36x    
  
  frame=  156 fps= 33 q=24.8 size=     299kB time=00:00:06.24 bitrate= 392.3kbits/s dup=4 drop=0 speed=1.32x    
  
  frame=  169 fps= 32 q=24.8 size=     322kB time=00:00:06.76 bitrate= 389.7kbits/s dup=4 drop=0 speed=1.29x    
  
  frame=  182 fps= 32 q=24.8 size=     344kB time=00:00:07.28 bitrate= 387.4kbits/s dup=4 drop=0 speed=1.26x    
  
  frame=  195 fps= 31 q=24.8 size=     367kB time=00:00:07.80 bitrate= 385.5kbits/s dup=4 drop=0 speed=1.24x    
  
  frame=  208 fps= 31 q=24.8 size=     390kB time=00:00:08.32 bitrate= 383.8kbits/s dup=4 drop=0 speed=1.22x    
  
  frame=  221 fps= 30 q=24.8 size=     413kB time=00:00:08.84 bitrate= 382.3kbits/s dup=4 drop=0 speed=1.21x   

  How can I grab the latest frames out of this live-stream image ? (OR is there a thread-safe way to clean the stream and only get the latest frame when I request ?)

• FFmpeg + iOS + lossy cellular connections

  9 novembre 2014, par Moss

  I am able to play an RTMP audio + video real-time stream on iOS with FFmpeg. Works fantastic when everything is on a solid WiFi connection.

  When I switch to a cellular connection (great signal strength and LTE/4G), av_read_frame() will intermittently block for an unacceptable amount of time. From what I can tell, it’s not that the cellular data connection just dropped, because I can reconnect immediately and start downloading more packets. In some cases, I’ve clocked 30+ seconds of hang time before it returns the next frame. When the next frame finally comes in, my real-time video stream is permanently delayed by the amount of time that av_read_frame() blocked.

  I attempted a work-around by using the AVIOInterruptCB interrupt callback to abort av_read_frame() if the function takes longer than 1 second to return. Here’s what that code looks like :

  - (void)readPackets {
  
      // Make sure FFmpeg calls our interrupt periodically
  
      _context->interrupt_callback.callback = interrupt_cb;
  
      _context->interrupt_callback.opaque = self;
  
  
  
      dispatch_async(_readPacketQueue, ^(void) {
  
          int err;
  
  
  
          while(true) {
  
              _readFrameTimeStamp = [[NSDate date] timeIntervalSince1970];
  
              err = av_read_frame(_context, &packet);
  
              _readFrameTimeStamp = 0;
  
  
  
              if(err) {
  
                  // Error - Reconnect the entire stream from scratch, taking 5-10 seconds
  
                  // And we know when av_read_frame() was aborted
  
                  // because its error code is -1414092869 ("EXIT")
  
              }
  
              else {
  
                  // Play this audio or video packet
  
              }
  
          }
  
     });
  
  }
  
  
  
  /**
  
   * Interrupt
  
   * @return 1 to abort the current operation
  
   */
  
  static int interrupt_cb(void *decoder) {
  
      if(decoder) {
  
          if(_readFrameTimeStamp != 0) {
  
              if([[NSDate date] timeIntervalSince1970] - _readFrameTimeStamp > 1) {
  
                  // Abort av_read_frame(), it's taking longer than 1 second
  
                  return 1;
  
              }
  
          }
  
      }
  
  }

  This definitely aborts av_read_frame() after 1 second, but unfortunately after I do this, future attempts to call av_read_frame() result in EIO errors (-5), which indicates that the connection has been severed.

  As a result, I am forced to fully reconnect the viewer, which takes 5-10 seconds. (avformat_open_input() takes 3-4 seconds, and then find the stream info again takes 2-3 seconds, and then start reading frames).

  The 5-10 second delay to fully reconnect is much better than waiting more than 10 seconds for av_read_frame() to unblock, and it’s much better than the real-time stream being delayed by a significant amount. But it’s much worse than being able to retry av_read_frame() immediately.

  From a cellular user’s perspective, their video locks up intermittently for 5-10 seconds while we reconnect the stream in the background from scratch, which isn’t a good user experience.

  What strategies are there to better way to manage av_read_frame() on a lossy cellular connection ?
  (Or strategies to improve the reconnect time ?)

• Revision 30970 : Début de compatibilité avec les squelettes Z. Reste à forcer la création ...

  17 août 2009, par vincent@… — Log

  Début de compatibilité avec les squelettes Z.
  Reste à forcer la création d’un menu "barrenav" quand on détecte qu’il y a un squelette Z d’activé.