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• very low latency streaming with ffmpeg using a webcam

  14 août, par userDtrm

  I'm trying to configure ffmpeg to do a real-time video streaming using a webcam. The ffmpeg encoder command I use is as follows.

  



  ffmpeg -f v4l2 -input_format yuyv422 -s 640x480 -i /dev/video0 -c:v libx264 -profile:v baseline -trellis 0 -subq 1 -level 32 -preset superfast -tune zerolatency -me_method epzs -crf 30 -threads 0 -bufsize 1 -refs 4 -coder 0 -b_strategy 0 -bf 0 -sc_threshold 0 -x264-params vbv-maxrate=2000:slice-max-size=1500:keyint=30:min-keyint=10: -pix_fmt yuv420p -an -f mpegts udp://192.168.1.8:5001


  



  The ffplay command used to display the video feed is,

  



  ffplay -analyzeduration 1 -fflags -nobuffer -i udp://192.168.1.8:5001


  



  However, I'm experiencing a latency of 0.5 - 1.0s latency in the video stream. Is there a way to reduce this to a number less than 100ms. Also, when I replace the v4l2 camera capture with a screen capture using x11grab, the stream is almost real-time and I experience no noticeable delays. Moreover, changing the encoder from x264 to mpeg2 had no effect on the latency. In addition, the statistics from the ffmpeg shows that the encoder is performing at a 30fps rate, which I believe indicates that the encoding is real-time. This leaves me with only one reason for the experienced delay.

  



  

  • Is there a significant delay in buffers when using v4l2 during video capturing in a webcam ?

  


  • I don't think the transmission delay is in effect in this case as I see no latencies when screen capture is used under the same conditions.

  


  • Can this latency be further reduced ?. Can someone think of a different encoder configuration to be used instead of the one that I've been using ?

  


  


• How to save recorded ffmpeg webcam video to red5

  20 juillet 2014, par user3451310

  im trying to make a webcam recording program that can be accessed remotely by other users. i completed the recording locally but when i try to save it to red5 rtmp ://localhost/oflaDemo/streams/output.flv, no output produced to the streams directory and i don’t know how to stream it from other users while recording. can someone help me on this problem ?tnx heres my code :

  Thread webcam = new Thread()
  public void run()

      String fileName = new SimpleDateFormat("yyyy-MM-dd-hhmm").format(new Date());
  
     try {  
  
     OpenCVFrameGrabber grabber = new OpenCVFrameGrabber(0);  
  
     grabber.start();  
  
     opencv_core.IplImage grabbedImage = grabber.grab();  
  
     CanvasFrame canvasFrame = new CanvasFrame("Video recorder");  
  
     canvasFrame.setCanvasSize(grabbedImage.width(), grabbedImage.height());  
  
     grabber.setFrameRate(grabber.getFrameRate());  
  
  
  
  
  
  
  
     FFmpegFrameRecorder recorder = new FFmpegFrameRecorder("rtmp://localhost/oflaDemo/streams/output.flv", 800, 600);
  
  
  
     recorder.setFormat("flv");  
  
     recorder.setFrameRate(6);  
  
     recorder.setVideoBitrate(1024 * 1024); 
  
  
  
  
  
  
  
  
  
     recorder.start();
  
  
  
  
  
  
  
     while (canvasFrame.isVisible() && (grabbedImage = grabber.grab()) != null) {  
  
       canvasFrame.showImage(grabbedImage);  
  
       recorder.record(grabbedImage);  
  
     }  
  
     recorder.stop();  
  
     grabber.stop();  
  
     canvasFrame.dispose();  
  
  
  
  
  
     recorder.record();
  
  
  
   } catch (FrameGrabber.Exception ex) {  
  
     Logger.getLogger(web.class.getName()).log(Level.SEVERE, null, ex);  
  
   } catch (FrameRecorder.Exception ex) {  
  
     Logger.getLogger(web.class.getName()).log(Level.SEVERE, null, ex);  
  
   }  

   ;
  webcam.start() ;

  }        

• How do I add a delay to a live stream sourced from webcam (v4l2) with FFMPEG ?

  20 novembre 2018, par David

  How can I use FFMPEG to add a delay to a stream being sent from a (v4l2) webcam to a media server ?

  The use case here is something like a security camera where I want to be able to stream video to a server when something is detected in the video. The easiest way to ensure the event of interest is captured on the video is to use FFMPEG to stream from the camera to a virtual loopback device with an added delay. That loopback device can then be used to initiate live streaming when an even of interest occurs.

  In GStreamer, I would accomplish a delay of this sort with the queue element’s min-threshold-time parameter. For example the following (much-simplified) example pipeline adds a 2 second delay to the output coming from a v4l2 webcam before displaying it :

  gst-launch-1.0 v4l2src device=/dev/video1 ! queue max-size-buffers=0 max-size-time=0 max-size-bytes=0 min-threshold-time=2000000000 ! xvimagesink

  How do I accomplish the same thing with FFMPEG ? There are some technical challenges that prevent us from using GStreamer for this.

  I have investigated the itsoffset option for this, but as far as I can tell it is only usable for already-recorded files, and it is not clear what a good alternative would be.