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• Using python subprocess from bytes to bytes

  5 mai 2020, par thorwhalen

  I can convert a mp4 to wav, using ffmpeg, by doing this :

  



  ffmpeg -vn test.wav  -i test.mp4 


  



  I can also use subprocess to do the same, as long as my input and output are filepaths.

  



  But what if I wanted to use ffmpeg directly on bytes or a "file-like" object like io.BytesIO() ?

  



  Here's an attempt at it :

  



  import subprocess
from io import BytesIO
b = BytesIO()

with open(rjoin('test.mp4'), 'rb') as stream:
    command = ['ffmpeg', '-i']
    proc = subprocess.Popen(command, stdin=subprocess.PIPE, stdout=b)
    proc.communicate(input=stream.read())
    proc.wait()
    proc.stdin.close()
    proc.stdout.close()


  



  Gives me :

  



  ---------------------------------------------------------------------------&#xA;UnsupportedOperation                      Traceback (most recent call last)&#xA; in <module>&#xA;      5 with open(rjoin(&#x27;test.mp4&#x27;), &#x27;rb&#x27;) as stream:&#xA;      6     command = [&#x27;ffmpeg&#x27;, &#x27;-i&#x27;]&#xA;----> 7     proc = subprocess.Popen(command, stdin=subprocess.PIPE, stdout=b)&#xA;...&#xA;   1486                 # Assuming file-like object&#xA;-> 1487                 c2pwrite = stdout.fileno()&#xA;   1488 &#xA;   1489             if stderr is None:&#xA;&#xA;UnsupportedOperation: fileno&#xA;</module>

  


• lavc/cbs_av1 : Save more frame ordering information

  20 mars 2024, par Mark Thompson

  lavc/cbs_av1 : Save more frame ordering information
  This is wanted by the Vulkan decoder.
  

  • [DH] libavcodec/cbs_av1.h
  • [DH] libavcodec/cbs_av1_syntax_template.c

• FFmpeg compose, multi layers and filters, need kindly help 

  9 octobre 2019, par jadeshohy

  Pretty new to FFmpeg. We would like to use FFmpeg as a important part of an AR project.

  Currently, we find it is not easy for us.

  We want to compose the footages with FFmpeg.

  We got 5 layers, wanted to blend them with specific mode, like the things in After Effects.

  • layer-1/ [A.webm] video，vp9 codec, which has a transparent BG,has to be added as [normal mode]

  • layer-2/ [B.mp4] video, optical-flare things with black BG,has to be added as [screen mode]

  • layer-3/ [C.mp4] video, some motion graphic things with light BG,has to be added as [overlay mode]

  • layer-4/ [BG.MP4], backgound things, has to be added as [normal mode]

  After we blend those 4 (like pre-compose,use blend filter), we want to add another layer-5/[icon.png] which is the special icon.

  Layer-5 need to overlay the pre-compose. We have to overlay it at the special position (use overlay filter ?).

  Cause [icon.png] may change frequently. we want to deal with that after the 4 layer blending.

  But at the first step, when we set normal mode for layer-1 in blend filter, layer-1 [A.webm] lost the transparent BG，it gave us a black BG which block all other things.
  Blend filter can not handle the alpha channel of vp9 webm ?
  When we set the mode of layer-1 to screen mode,the translucent thing was not what we need.

  Could you please give us some commands to achieve the blend above ?

  The commands that are really work will be extremely useful for our FFmpeg initiation.