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• FFmpeg returns empty byte when retrieving frames with python

  13 août 2020, par Ronald Saunfe

  I am trying to retrieve frames from a video frame by frame using ffmpeg which i downloaded here but i get an empty response as byte :
i need someone to outline what my problem is.I got the solution from a blog here
Here is my source code :

  


  import subprocess as sp

command=['bin\\ffmpeg.exe',
'-i','%s'%self.source,
'-f','image2pipe',
'-pix_fmt','rgb24',
'-vcodex','rawvideo','-']

self.pipe = sp.Popen(command, stdout = sp.PIPE, bufsize = 10**8)
Raw_image = self.pipe.stdout.read(420*360*3)


  


• Encoding of video returns 0, and nothing written to the output file

  14 juillet 2014, par AnilJ

  I have written a code to record the webcam feed into a file on disk. I am attempting to do this using IContainer class rather than IMediaWriter class. I am pasting the code snippet below showing important sections of the code.

  The problem I am facing is that nothing is being written to the file. Some of the observations I have made are as follows :

  1. In the Record() function, the ’while’ loop is kicked off, but the mVideoEncoder.encodeVideo(packet, frame, offset) ; method always returns zero (0). This results in no picture complete and no data is being written to the output file. Can you please provide clue as to what is missing ?
  2. I checked that the frame size is 80640, which confirms that frame has data.
  3. I see that only header and trailer is being written to the file.

  Let me know if you need any other information.

  public class WebcamRecorder {
  
  
  
      private boolean StartVideoEncoder() {
  
  
  
          boolean result = true;
  
  
  
          // Open a container
  
          mPositionInMicroseconds = 0;
  
          mOutputContainer = IContainer.make();
  
          mOutputContainer.open(mOutputFileName, IContainer.Type.WRITE, null);
  
  
  
          // Create the video stream and get its coder
  
          ICodec videoCodec = ICodec.findEncodingCodec(ICodec.ID.CODEC_ID_H264);
  
          IStream videoStream = mOutputContainer.addNewStream(videoCodec);
  
          mVideoEncoder = videoStream.getStreamCoder();
  
  
  
          // Setup the stream coder
  
          mFrameRate = IRational.make(1, 30);
  
          mVideoEncoder.setWidth(Constants.RESAMPLE_PICT_WIDTH);
  
          mVideoEncoder.setHeight(Constants.RESAMPLE_PICT_HEIGHT);
  
          mVideoEncoder.setFrameRate(mFrameRate);
  
          mVideoEncoder.setTimeBase(IRational.make(mFrameRate.getDenominator(),
  
                                    mFrameRate.getNumerator()));
  
          mVideoEncoder.setBitRate(350000);
  
          mVideoEncoder.setNumPicturesInGroupOfPictures(30);
  
          mVideoEncoder.setPixelType(IPixelFormat.Type.YUV420P);
  
          mVideoEncoder.setFlag(IStreamCoder.Flags.FLAG_QSCALE, true);
  
          mVideoEncoder.setGlobalQuality(0);
  
  
  
          // Open the encoder
  
          mVideoEncoder.open(null, null);
  
  
  
          // Write the header
  
          mOutputContainer.writeHeader();
  
  
  
          return result;
  
      }
  
  
  
      public void Record() {
  
  
  
          picture = GetNextPicture();
  
          image = Utils.videoPictureToImage(picture);
  
          // convert to the right image type
  
          BufferedImage bgrScreen = ConvertToType(image, BufferedImage.TYPE_3BYTE_BGR);
  
          IConverter converter = ConverterFactory.createConverter(bgrScreen, mVideoEncoder.getPixelType());
  
          IVideoPicture frame = converter.toPicture(bgrScreen, mPositionInMicroseconds);
  
          frame.setQuality(0);
  
  
  
          IPacket packet = IPacket.make();
  
          int offset = 0;
  
          while (offset < frame.getSize()) {
  
              int bytesEncoded = mVideoEncoder.encodeVideo(packet, frame, offset);
  
              if (bytesEncoded < 0) {
  
                  throw new RuntimeException("Unable to encode video.");
  
              }
  
              offset += bytesEncoded;
  
  
  
              if (packet.isComplete()) {
  
                  System.out.println("Packet is complete");
  
                  if (mOutputContainer.writePacket(packet) < 0) {
  
                      throw new RuntimeException(
  
                              "Could not write packet to container.");
  
                  }
  
  
  
                  // Update frame time
  
                  mPositionInMicroseconds += (mFrameRate.getDouble() * Math.pow(1000, 2));
  
                  break;
  
              }
  
          }
  
      }
  
  
  
      public void Cleanup() {
  
  
  
          if (mOutputContainer != null) {
  
              mOutputContainer.writeTrailer();
  
              mOutputContainer.close();
  
              // mOutputContainer.flushPackets();
  
          }
  
  
  
          if (mVideoEncoder != null) {
  
              mVideoEncoder.close();
  
          }
  
      }
  
  }

• avfilter/vf_libplacebo : don't force dovi frames to bt.2020-ncl

  30 octobre 2023, par Niklas Haas

  avfilter/vf_libplacebo : don't force dovi frames to bt.2020-ncl
  This is at odds with the YUV matrix negotiation API, in which such
  
  dynamic changes in YUV encoding are no longer easily possible. There is
  
  also no really strong motivating reason to do this, since the choice of
  
  YUV matrix is essentially arbitrary and not actually related to the
  
  Dolby Vision decoding process.
  

  • [DH] libavfilter/vf_libplacebo.c