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• Saving Raw Uncompressed Video Files using OpenCv, Gstreamer, and/or FFMPEG ?

  20 septembre 2022, par adav0033

  I have been trying to implement the cv::VideoWriter function from OpenCV to generate a an uncompressed (raw) video file. I started this because of a statement within the OpenCV Documentation which I will link here along with the statement.

  


  cv::VideoWriter::VideoWriter    (   const String &  filename,
int     fourcc,
double  fps,
Size    frameSize,
bool    isColor = true 
)       


  


  "If FFMPEG is enabled, using codec=0 ; fps=0 ; you can create an uncompressed (raw) video file."

  


  Ref. https://docs.opencv.org/3.4/dd/d9e/classcv_1_1VideoWriter.html

  


  However whilst troubleshooting the function I came across the refuting statement,

  


  " VideoCapture and VideoWriter do not provide interface to access raw compressed video stream, except maybe MJPEG in some cases.
Make sure you actually use FFmpeg backend by setting apiPreference parameter : VideoWriter("outfile.avi", cv2.CAP_FFMPEG, ...)"

  


  Ref. https://github.com/opencv/opencv/issues/14573

  


  I am now confused about how I go about writing the cv::VideoWriter function to satisfy the requirements to create a raw uncompressed video file (.avi) and if it is even possible. If it is not possible how do I achieve the outcome of saving an raw uncompressed video file, as I assume it would use some combination of FFMPEG, OpenCV,or Gstreamer.

  


  Note : My code is implemented in c++

  


• dnn : remove type cast which is not necessary

  22 janvier 2021, par Guo, Yejun

  dnn : remove type cast which is not necessary
  

  • [DH] libavfilter/dnn/dnn_backend_native.c
  • [DH] libavfilter/dnn/dnn_backend_native_layer_avgpool.c
  • [DH] libavfilter/dnn/dnn_backend_native_layer_conv2d.c
  • [DH] libavfilter/dnn/dnn_backend_native_layer_dense.c
  • [DH] libavfilter/dnn/dnn_backend_native_layer_depth2space.c
  • [DH] libavfilter/dnn/dnn_backend_native_layer_mathbinary.c
  • [DH] libavfilter/dnn/dnn_backend_native_layer_mathunary.c
  • [DH] libavfilter/dnn/dnn_backend_native_layer_maximum.c
  • [DH] libavfilter/dnn/dnn_backend_native_layer_pad.c
  • [DH] libavfilter/dnn/dnn_backend_openvino.c
  • [DH] libavfilter/dnn/dnn_backend_tf.c

• How to generate a GIF thumbnail from a video without saving individual frames to disk ?

  12 mars 2023, par Rabie Daddi

  I have a Node.js script that uses fluent-FFmpeg to generate a GIF thumbnail from a video for the first 4 seconds. Currently, the script saves individual frames as PNG images to disk, and then reads them back in to generate the GIF. However, this creates a lot of unnecessary I/O.

  


  Is there a way to modify the script to generate the GIF directly from the video frames, without saving them to disk first ? Ideally, I would like to do this while still using FFmpeg for the processing.

  


  Here's the current code for generating the frames and the GIF :

  


  function generateFrames(videoUrl) {
  return new Promise((resolve, reject) => {
    ffmpeg(videoUrl)
      .setStartTime(0) // start at 0 seconds
      .setDuration(4) // cut 4 seconds
      .videoFilters('scale=if(gte(iw\\,ih)\\,min(600\\,iw)\\,-2):if(lt(iw\\,ih)\\,min(600\\,ih)\\,-2)')
      .fps(4)
      .output('output/img%04d.png') // output file pattern with %04d indicating a sequence number with four digits
      .on('end', () => {
        console.log('GIF generated successfully!');
        resolve()
      })
      .on('error', (err) => {
        console.log('Error generating GIF: ' + err.message);
        reject()
      })
      .run();
  });
}

function generateGif() {
  const inputPattern = 'output/img%04d.png';
  const outputFilename = 'output/output2.gif';

  ffmpeg(inputPattern)
    .inputFPS(9)
    .output(outputFilename)
    .on('error', (err) => {
      console.log('Error generating GIF: ' + err.message);
    })
    .run();
}


execute = async () => {
  await generateFrames('video.mp4')
  generateGif()
}

execute()


  


  Any help or suggestions would be greatly appreciated. Thank you !