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• subprocess.Popen crashes when run in background

  17 mars 2016, par user2810298

  In a program I’m working with right now, I try to check for the version of FFMPEG that is installed on the users machine. This works perfectly fine by using subprocess.Popen when run in the foreground OR when run in a detached screen.

  However, when you run it in the background without screen (e.g. COMMAND &> /dev/null &) this process crashes the program. (see below) I’ve seen some people having similar issues on the web, but I still can’t seem to fix this...

  I’ve Any ideas ?

  version_ffmpeg = subprocess.Popen(["ffmpeg","-version"],stdout=subprocess.PIPE,stderr=None)
  
  
  
  f_out = version_ffmpeg.communicate()
  
  (then...)
  
  if f_out --> 3rd word contains --> etc.

• Cut .mkv Video using ffmpeg without changing original bitrate

  23 janvier 2021, par benito_h

  I accidently said an unappropriate swear word during an educational video (good start I know). So I would like to remove this section from the .mkv video. However I would like the video and audio bitrate and quality unchanged.

  


  First, I tried cutting the video slightly after the relevant time stamp without reencoding it, using for example

  


  ffmpeg -i input.mkv -ss 00:01:09.200 -c copy -t 4:11 output.mkv


  


  but this way the first couple of seconds seem to get lost.

  


  Is there a way to remove the relevant segment (01:08.800 to 01:09.200) while maintaining the same bitrate / quality for audio and video ? Since only formulas are shown, a slight out-of-sync wouldnt even matter.

  


• ffmpeg : avfilter's anull says "Rematrix is needed between stereo and 0 channels but there is not enough information to do it"

  12 juillet 2017, par kuanyui

  I’m trying to write a transcoder according to FFMpeg’s official example with ffmpeg 3.2.4 (official prebuild Win32), and try to transcode a video with stereo audio stream source (from avformat’s dshow).

  In the example code, which passes anull into avfilter_graph_parse_ptr() for audio stream, and "time_base=1/44100:sample_rate=44100:sample_fmt=s16:channels=2:channel_layout=0x3" is passed into avfilter_graph_create_filter(), occurs error in the following avfilter_graph_config() :

  [auto-inserted scaler 0 @ 32f77600] w:iw h:ih flags:'bilinear' interl:0
  
  [Parsed_null_0 @ 2e9d79a0] auto-inserting filter 'auto-inserted scaler 0' between the filter 'in' and the filter 'Parsed_null_0'
  
  [swscaler @ 3331bfe0] deprecated pixel format used, make sure you did set range correctly
  
  [auto-inserted scaler 0 @ 32f77600] w:1920 h:1080 fmt:yuvj422p sar:1/1 -> w:1920 h:1080 fmt:yuv420p sar:1/1 flags:0x2
  
  [libmp3lame @ 2e90a360] Channel layout not specified
  
  [in @ 3866e8a0] tb:1/44100 samplefmt:s16 samplerate:44100 chlayout:0x3
  
  [Parsed_anull_0 @ 330e8820] auto-inserting filter 'auto-inserted resampler 0' between the filter 'in' and the filter 'Parsed_anull_0'
  
  [auto-inserted resampler 0 @ 330e8dc0] [SWR @ 3809b620] Rematrix is needed between stereo and 0 channels but there is not enough information to do it
  
  [auto-inserted resampler 0 @ 330e8dc0] Failed to configure output pad on auto-inserted resampler 0

  I’ve googled for days but didn’t find any clue for it. Doesn’t what anull do is only "Pass the audio source unchanged to the output", why libav want to resample stereo to 0 channel ? What’s going wrong ?