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• How to get frame-by-frame audio from the video in python

  7 juin 2023, par Usman Arshad

  So,first of all the description of my program is that I am viewing a video using opencv and whenever I press "p" the video paused for 5 seconds.At last I am saving that updated video in the same directory.I want to add audio to this video and whenever "p" pressed the audio must also be stopped for 5 second until next frame.

  


  import cv2

def save_frames(frames, output_filename, fps):
    # Get video information from the first frame
    height, width, _ = frames[0].shape

    # Create a VideoWriter object to save the frames
    fourcc = cv2.VideoWriter_fourcc(*'mp4v')
    output = cv2.VideoWriter(output_filename, fourcc, fps, (width, height))

    # Write each frame to the video file
    for frame in frames:
        output.write(frame)

    # Release the VideoWriter
    output.release()
    
def main():
    # Load the video
    video_path = 'input_video.mp4'
    cap = cv2.VideoCapture(video_path)


    frames = []
    fps = cap.get(cv2.CAP_PROP_FPS)

    while cap.isOpened():
        # Read the current frame
        ret, frame = cap.read()

        if not ret:
            break

        # Display the frame
        cv2.imshow('Video', frame)

        # Append the frame to the list
        frames.append(frame)
        # Wait for key press
        key = cv2.waitKey(int(1000 / fps))

        if key == ord('p'):
            # Pause the video for 5 seconds
            paused = True
            for _ in range(int(fps * 5)):
                frames.append(frame)
                cv2.waitKey(int(1000 / fps))
            paused = False

    # Release the VideoCapture
    cap.release()

    # Save the frames to a video file
    output_filename = 'output.mp4'
    save_frames(frames, output_filename, fps)

if __name__ == '__main__':
    main()


  


• Processing .Raw images using ffmpeg or OpenCV

  23 février 2013, par Ahmed Kato

  After reading Wikipedia page of Raw image format which is the digital negative of any image.

  To be viewed or printed, the output from a camera's image sensor has
  to be processed, that is, converted to a photographic rendering of the
  scene, and then stored in a standard raster graphics format such as
  JPEG. This processing, whether done in-camera or later in a raw-file
  converter, involves a number of operations, typically including

  I have some .raw files grabbed from my Logitech c920 using v4l2 example but when I display the image it looks like this :
  a raw image where in other frames I can see my shadow

  Does anyone knows how to process such files to see the complete frame ?

  Here is a link to the original .raw file

• Decoding H.264 stream using FFmpeg on Java

  25 mai 2020, par maru2213

  I'm trying to decode H.264 stream, which is sent over Socket from an Android application to a computer. And I also want to show the decoded stream using JavaFX. I searched much hours, and decided to use JavaCV / FFmpeg. However I got error from FFmpeg. (I was inspired by this code)

  



  Questions :

  



  

  • Why does FFmpeg make error ?

  


  • Is it a correct way to convert AVFrame to javafx.scene.image.Image ?

  


  



  I'm using :

  



  

  • javacv-platform 1.4.4

  


  • ffmpeg-platform 4.1-1.4.4

  


  



  Code :

  



  This is a part of import and class fields, and method which runs once at the first time. (Actually the content of initialize() is wrapped by try catch.)

  



      import javafx.scene.image.Image;

    private avcodec.AVCodec avCodec;
    private avcodec.AVCodecContext avCodecContext;
    private avutil.AVDictionary avDictionary;
    private avutil.AVFrame avFrame;

    public void initialize() {
        avCodec = avcodec_find_decoder(AV_CODEC_ID_H264);
        if (avCodec == null) {
            throw new RuntimeException("Can't find decoder");
        }
        avCodecContext = avcodec_alloc_context3(avCodec);
        if (avCodecContext == null) {
            throw new RuntimeException("Can't allocate decoder context");
        }
        int result = avcodec_open2(avCodecContext, avCodec, (AVDictionary) null);
        if (result < 0) {
            throw new RuntimeException("Can't open decoder");
        }
        avFrame = av_frame_alloc();
        if (avFrame == null) {
            throw new RuntimeException("Can't allocate frame");
        }
    }


  



  And this is a method which is called every time when I receive a packet from Android. byte[] data is the packet data starting with 0x00, 0x00, 0x00, 0x01.

  



  The place where I get error is number_of_written_bytes. It always gets <0.

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      private void decode(byte[] data) {
        AVPacket avPacket = new AVPacket();
        av_init_packet(avPacket);
        avPacket.pts(AV_NOPTS_VALUE);
        avPacket.dts(AV_NOPTS_VALUE);
        BytePointer bytePointer = new BytePointer(data);
        bytePointer.capacity(data.length);
        avPacket.data(bytePointer);
        avPacket.size(data.length);
        avPacket.pos(-1);

        avcodec_send_packet(avCodecContext, avPacket);
        int result = avcodec_receive_frame(avCodecContext, avFrame);
        if (result >= 0) {
            int bufferOutputSize = av_image_get_buffer_size(avFrame.format(), avFrame.width(), avFrame.height(), 16);
            Pointer pointer = av_malloc(bufferOutputSize);
            BytePointer outputPointer = new BytePointer(pointer);
            int number_of_written_bytes = av_image_copy_to_buffer(outputPointer, bufferOutputSize, avFrame.data(), avFrame.linesize(), avFrame.chroma_location(), avFrame.width(), avFrame.height(), 1);
            if (number_of_written_bytes < 0) {
                //The process always come here.
                throw new RuntimeException("Can't copy image to buffer");
            }

            System.out.println("decode success");
            Image image = new Image(new ByteArrayInputStream(outputPointer.asBuffer().array()));
        } else {
            System.out.println("decode failed");
        }
    }


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