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• FFMPEG Frame-exact Video Cropping

  17 décembre 2020, par Wilan

  Goal : To crop a video at a specific frame using FFMPEG

  


  Problem : Video freezes at the end for 1s

  


  I'm new to FFMPEG, so not sure if any other details are needed to debug this.

  


  import subprocess
import datetime

# Calculate start and end times in hh:mm:ss.ms
start_frame, end_frame = (9553, 10181)
start_time = str(datetime.timedelta(seconds=start_frame/fps))
end_time = str(datetime.timedelta(seconds=end_frame/fps))
            
cmd = ['ffmpeg', '-y', '-ss', start_time, '-to', end_time, '-i', input_path, '-c', 'copy', clip_path]
subprocess.call(cmd)


  


  Values :

  


  Start Frame: 9553
End Frame: 10181
Start Time: 0:06:22.120000
End Time: 0:06:47.240000


  


• FFMPEG : Remove silence with exact INTERVALS detected by silencedetect Filter

  29 mai 2021, par AfricanMamba

  I am trying to remove silence given the specific intervals given the output of the silencedetect filter. I recently read this post, but in my case, I want to use ONLY the intervals produced by the filter while using the same noise threshold. Here is what I have tried and the issues I am running into.

  


  After running the ffprobe :

  


  Input #0, wav, from 'audio.wav':
  Metadata:
    encoder         : Lavf58.76.100
  Duration: 00:00:56.21, bitrate: 1536 kb/s


  


  Here you can see that the video is exactly 56.21 seconds.

  


  After running silencedetect it produces an interval of silence with a threshold of -20dB :

  


  [silencedetect @ 000001dd38cead80] silence_start: 0
[silencedetect @ 000001dd38cead80] silence_end: 4.5631 | silence_duration: 4.5631
[silencedetect @ 000001dd38cead80] silence_start: 13.320
[silencedetect @ 000001dd38cead80] silence_end: 17.5232 | silence_duration: 4.2032


  


  After running this, I expected after using silenceremove, it would remove 8.7663 seconds of audio and the video would trim down to about 47.4437 seconds.

  


  The command silenceremove :

  


  ffmpeg -i audio.wav -af silenceremove=stop_periods=-1:stop_threshold=-20dB:window=0 output.wav


  


  After listening to the output I noticed that it cut out different regions of the audio that were not a part of the two intervals I was expecting it to remove. I ran the output in fprobe again to see the results :

  


  Input #0, wav, from 'output.wav':
  Metadata:
    encoder         : Lavf58.76.100
  Duration: 00:00:33.48, bitrate: 1536 kb/s


  


  It removed much more than the expected 8 seconds. Does anyone happen to know the command input parameters I need to use in order for it to only remove the intervals that it detected in silencedetect ? I do not think using duration will be the best tool because 1 : the two durations are different 2 : I am trying to create a program that removes the segments of silence automatically without me having to hard code it. Does anyone happen to know how I can solve this issue ? All help is appreciated !

  


• How to get an exact audio channel layout info by ffmpeg ?

  22 janvier 2020, par xin xu

  How to get a audio channel layout info by ffmpeg ?
  For example,if audio is 5.1 then I want to get info following like
  FL+FR+FC+LFE+BL+BR