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• building static ffmpeg library for Android under windows 7

  29 mai 2013, par Zhenya

  I know that this has been asked several times, but I've never found any clear step by step and conclusive answer.

  How can I compile ffmpeg for Android, under windows 7 ?
  What are the steps ? Is there a project or wiki on the internet where to find this ?

  All I've found are steps to run under Ubuntu, or purely linux, but nothing to generate a static library for android, to be build under windows 7.

  Thanks

• Find files that have been only once modified in last 24 hours [duplicate]

  4 janvier 2020, par Vijay Chandra

  This question already has an answer here :

  • How to find the number of times particular file has been modified in given time range [closed]
    
    2 answers
    

  I’m using this command to get all modified files in the last 24 hours on Ubuntu.

  find -type f -name "*.mp4" -mtime -1 -printf "%f\n"

  How can I modify this to detect that a file has been modified more than a single time ? And if so, ignore it.

  I need this to create a watermarking script which will find the latest files within 24 hours and save the list to a text file and with the help of this text file, I use ffmpeg to watermark the videos and move them to the original location.

  If I do this, the find command considers the new updated video as a modified file and adds the watermark repeatedly.

  My code is attached below :

  #!/bin/bash
  
  find -type f -name "*.mp4" -mtime -1 -printf "%f\n" >> filename='/home/domain.com/public_html/admin_panel/public_html/uploads/mp4/temp/file.txt'
  
  all_lines=`cat $filename` 
  
  for item in $all_lines; do  
  
    cp $item /home/domain.com/public_html/admin_panel/public_html/uploads/mp4/temp 
  
    ffmpeg -i $item -i watermark.png -filter_complex "[1][0]scale2ref=w='iw*30/100':h='ow/mdar'[wm][vid];[vid][wm]overlay=(main_w-overlay_w):(main_h-overlay_h)"
  
  -y /home/domain.com/public_html/admin_panel/public_html/uploads/mp4/temp/$item 
  
  done

• 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.