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• Opencv Java VideoCapture image corruption, possibly frame rate driven

  30 septembre 2019, par A. Scientist

  I’m having difficulty with OpenCV java cleanly capturing an image from a video stream from a video capture card. So far none of the other advice around here has helped me (I’ve spent a whole day looking through it). Each time it returns a corrupt or blank image so I suspect frame rate issues, although I am able to use ffmpeg to capture an image of it cleanly (for project reasons I strongly prefer to this in Java). Both ffmpeg and opencv report they are capturing at 30 fps and using the YUYV format through v4l2.
  My code :

  Mat frame = new Mat();
  
  VideoCapture camera = new VideoCapture(0);
  
  int fcc = VideoWriter.fourcc('Y', 'U', 'Y', 'V');
  
  System.out.println(camera.get(Videoio.CAP_PROP_FPS)+
  
  " "+camera.get(Videoio.CAP_PROP_FOURCC)+" "+fcc);
  
  wait_for(10000);//wrapper for TimeUnit.MILLISECONDS.sleep()
  
  while (!camera.isOpened()){//this part never runs
  
      wait_for(50);
  
      if(c++>500){
  
          break;
  
      }
  
  }
  
  while (true) {
  
          if (camera.read(frame)) {
  
              if(Core.sumElems(nframe).val[0]>Math.pow(10, 4)){
  
                  Imgcodecs.imwrite("/home/anon/testimg.jpg", frame);
  
                  break;
  
              }
  
          }
  
   }

  

• How to ensure that ffmpeg libraries uses/ not uses GPU

  31 mai 2021, par zimopisec

  My library ( Linux, Debian) uses FFMpeg libraries ( avformat, avcodec, swscale etc) for reading video stream from network cameras. Actually, I need to capture each video frame from network camera, decode it, scale and store in memory- and other thread pass this data to calling program for display.

  


  Problem is, that all works in CPU and take a huge amount of CPU resource. How can I enforce usage of GPU accelerator for processing ?

  


  I have video card : VGA compatible controller : Intel Corporation HD Graphics 620 (rev 02)

  


  My decode thread look like this ( I omit declarations, error handling etc, so pls don't look for grammar mistakes :)))

  


  fmt = avformat_alloc_context(); 
//initialising, setting option by av_dict_set
// finding video stream index
***
 // finding decoder and allocate its contexts

    frame = av_frame_alloc();

    while ( av_read_frame(ctx->fmt, &pkt) >= 0) 
    {
        AVPacket orig_pkt = pkt;

         avcodec_send_packet(ctx->dec_ctx, pkt);
         avcodec_receive_frame(ctx->dec_ctx, frame);
            *** 
// get buffer allocated for store of frame data
             buff = get_free_buffer(ctx);
        sws_scale(ctx->sws, (const uint8_t * const*)frame->data, 
        frame->linesize, 0, ctx->dec_ctx->height, buff->data,
        buff->linesize);
            ret = decode_packet(ctx, frame, &pkt, &got_frame);
            if (ret < 0)
                break;
            pkt.data += ret;
            pkt.size -= ret;
        }
        while (pkt.size > 0);

        av_packet_unref(&orig_pkt);
    }
*****  


  


• JavaCV FFMpegRecorder streams video not displayed properly

  20 août 2015, par Mo Adel

  I have been in loop for 5 days trying to implement JavaCV with FFmpegRecorder, Having figured out that i have to use OpenCvFrameConverter to conert IplImage to frame, I finally managed to see some video over the stream. but now the problem seems to be that the audio works perfect and clearly, but video is not displayed properly.

  

  Beside that there is a massive delay on the stream, well over 40sec, when i thought RTMP had 2-4sec delay,

  Here is some code :

  FFmpegFrameRecorder Initialization

  recorder = new FFmpegFrameRecorder(ffmpeg_link, screenWidth, screenHeight, 1);
  
      recorder.setFormat("flv");
  
      recorder.setSampleRate(44100);
  
      recorder.setAudioCodec(avcodec.AV_CODEC_ID_AAC);
  
      recorder.setVideoCodec(avcodec.AV_CODEC_ID_FLV1);// AV_CODEC_ID_FLV1
  
      recorder.setVideoOption("preset", "ultrafast"); 
  
      recorder.setFrameRate(30);

  And here is my SurfaceChanged and PreviewFrame Methods

   public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
  
  
  
          Camera.Parameters camParams = mCamera.getParameters();
  
          List sizes = camParams.getSupportedPreviewSizes();         
  
  
  
          android.hardware.Camera.Size z = getOptimalPreviewSize(sizes, screenWidth, screenHeight);
  
          int imageWidth = z.width;
  
          int imageHeight = z.height;
  
          camParams.setPreviewSize(imageWidth, imageHeight);
  
          mCamera.setParameters(camParams);
  
  
  
          for(int[] arr : camParams.getSupportedPreviewFpsRange()){
  
              Log.e(LOG_TAG, "Supported range: " + arr[0] + " - " + arr[1]);
  
          }
  
  
  
          Camera.Parameters framerateAttempts = mCamera.getParameters();
  
          camParams.setPreviewFrameRate(frameRate);
  
          Log.v(LOG_TAG,"Preview Framerate: " + camParams.getPreviewFrameRate());
  
          Display display = ((WindowManager)getSystemService(WINDOW_SERVICE)).getDefaultDisplay();
  
  
  
          if(display.getRotation() == Surface.ROTATION_0)
  
          {
  
              mCamera.setDisplayOrientation(90);
  
          }
  
  
  
          if(display.getRotation() == Surface.ROTATION_90)
  
          {
  
          }
  
  
  
          if(display.getRotation() == Surface.ROTATION_180)
  
          {
  
          }
  
  
  
          if(display.getRotation() == Surface.ROTATION_270)
  
          {
  
              mCamera.setDisplayOrientation(180);
  
          }
  
          camParams.setFocusMode(Parameters.FOCUS_MODE_CONTINUOUS_PICTURE);
  
          mCamera.setParameters(framerateAttempts);
  
  
  
          startPreview();
  
      }
  
  
  
   @Override
  
      public void onPreviewFrame(byte[] data, Camera camera) {
  
          /* get video data */
  
          if (yuvIplimage != null && recording) {
  
              yuvIplimage.getByteBuffer().put(data);
  
  
  
              Log.v(LOG_TAG,"Writing Frame");
  
              try {
  
                  long t = 1000 * (System.currentTimeMillis() - startTime);
  
                  if (t > recorder.getTimestamp()) {
  
                      recorder.setTimestamp(t);
  
                  }
  
  
  
                  OpenCVFrameConverter.ToIplImage converterToMat = new OpenCVFrameConverter.ToIplImage();
  
                  Frame f = converterToMat.convert(yuvIplimage);
  
                  recorder.record(f);
  
              } catch (FFmpegFrameRecorder.Exception e) {
  
                  Log.v(LOG_TAG,e.getMessage());
  
                  e.printStackTrace();
  
              }
  
          }
  
      }