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• Revision 65d39f9fae : Merge "Palette experiment : encode color indices based on context" into nextgen

  27 mars 2015, par hui su

  Changed Paths :
   Modify /vp9/encoder/vp9_rdopt.c

  
  
  Merge "Palette experiment : encode color indices based on context" into nextgen

• how to define overlay video position and size ffmpeg electronJS ?

  26 mars 2022, par Nommiiee

  function overlayMaker(){
    
    ffmpeg()
    .on('end', onEnd )
    .on('progress', onProgress)
    .on('error', onError)
    .input(`${QuizicorderDir}/screen.webm`)
    .input(  `${QuizicorderDir}/webcam.webm`)
    .complexFilter([
        "[0:V]scale=1920:-4,pad=0:1080:0:(oh-ih)/2[vid];[vid][1:V]overlay"
    ])
    .outputFps(30)
    .output('./output-video.mp4')
    .run();
}


  


  I am using this function to create an overlay of the webcam video on top of the screen recorder video. I have defined the input file path to be the temp folder in windows as i am saving the recording there temperory.
The following image is the desired output


  


  and the output that i am getting is the following


  


• Slightly wrong color in MP4 videos written by PyAV

  26 septembre 2024, par Yossi Kreinin

  I am writing MP4 video files with the following PyAV-based code (getting input frames represented as numpy arrays - the sort produced by imageio.imread - as input) :

  


  class MP4:
    def __init__(self, fname, width, height, fps):
        self.output = av.open(fname, 'w', format='mp4')
        self.stream = self.output.add_stream('h264', str(fps))
        self.stream.width = width
        self.stream.height = height
        # these 2 lines can be removed and the problem still reproduces:
        self.stream.pix_fmt = 'yuv420p'
        self.stream.options = {'crf': '17'}
    def write_frame(self, pixels):
        frame = av.VideoFrame.from_ndarray(pixels, format='rgb24')
        packet = self.stream.encode(frame)
        self.output.mux(packet)
    def close(self):
        packet = self.stream.encode(None)
        self.output.mux(packet)
        self.output.close()


  


  The colors in the output MP4 video are slightly different (apparently darker) than the colors in the input images :

  


  Screen grab of an image viewer showing an input frame :

  


  

  


  Screen grab of VLC playing the output MP4 video :

  


  

  


  How can this problem be fixed ? I variously fiddled with the frame.colorspace attribute, stream options and VideoFrame.reformat but it changed nothing ; of course I could have been fiddling incorrectly.

  


  As you can see, the input has simple flat color regions, so I doubt it's any sort of compression artifact, eg YUV420 dropping some of the chroma info or other such.