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• Python subprocess or os.system not working with ffmpeg

  13 février 2024, par confused

  I've been trying to get this darn programming run since last night and cannot seem to get anything to work. I want to first trim the video and then resize the video. I'm reading which video and what to give the final name from a text file, over 780 lines long, quite a few videos.

  


  Thus far with every idea under the sun I have tried, subprocess and os.system, I can't get anything more than error statements or right now all I get is no file creation of any kind. How the heck do I get this to work correctly ?

  


  import ffmpeg
import subprocess
import os

os.chdir('/home/Downloads/SRs/')
a = open('SRt.txt', 'r')
b = a.readlines()
a.close()
for c in range(0, len(b)-1):
    words = list(b[c].split(" "))
    d = len(words)
    e = words[d-1]
    f = b[c].replace(e, 'FR' + str(c) + '.mp4')
    words[d-1] = 'FR' + str(c) + '.mp4'
    print(f)
    subprocess.call(f, shell=True)
    subprocess.call([
        'ffmpeg',
        '-i',
        "'FR' + str(c) + '.mp4'",
        '-vf scale=320:240',
        words[d-1],
        ])


  


  Here are some examples of what the original file would look like :

  


   ffmpeg -i SR.mp4 -ss 00:00:00 -to 00:01:22 -c:v copy -a copy CPH.mp4
 ffmpeg -i SR.mp4 -ss 00:01:24 -to 00:02:58 -c:v copy -a copy CG.mp4
 ffmpeg -i SR.mp4 -ss 00:02:59 -to 00:05:41 -c:v copy -a copy CSGP.mp4


  


  Nothing fancy just separating video in its own individual segments and then resaving it before resizing it.

  


  I tried :

  


  z=subprocess.call(f, shell=True, stdout=subprocess.PIPE)
print(z)


  


  But all I get is '1'.

  


  When I changed it to :

  


  z=subprocess.call(f, shell=True, stderr=subprocess.PIPE)
print(z)


  


  All I get is '1'.

  


  Maybe I'm doing something wrong.

  


• lavf : Remove codec_tag from dashenc and smoothstreamingenc

  30 juin 2017, par Martin Storsjö

  lavf : Remove codec_tag from dashenc and smoothstreamingenc
  Skip the codec_tag altogether here, to let the user (try to) set
  
  whichever codec/tag is preferred ; the individual chained muxer will
  
  reject invalid codecs anyway.
  (cherry picked from commit 61f589e31e84ae02d7ac6837f30f19c437b1fc2e)
  
  Signed-off-by : Derek Buitenhuis <derek.buitenhuis@gmail.com>
  

  • [DH] libavformat/dashenc.c
  • [DH] libavformat/smoothstreamingenc.c

• How to losslessly compress a sequence of slowly-changing images into a video ?

  26 juillet 2023, par Claude C

  I have a sequence of jpeg images captured like a timelapse, with the same dimension and changing slowly in order. I want to compress the size of the whole sequence while still able to recover each individual image with their raw pixel information unchanged.

  


  I googled and found that a possible solution is to compress it into a video, which exploits the strong temporal correlation (inter-frame redundancy) between consecutive frames, as suggested here. I tried ffmpeg libx264 but none of the option combinations seem to preserve frame quality and compress total size at the same time (-crf 0 keeps the quality but the size of the video is even larger than the input sequence).

  


  So my questions is,

  


  

  • What is the correct way to losslessly compress a sequence of slowly-changing images ?

  


  


  I can accept using softwares other than ffmpeg (as long as it is on windows or linux), doing color space conversion on raw images (if necessary). It is OK if a the compression is done without converting to videos. Thank you.