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• Is there an efficient way to use ffmpeg to create a huge quantity of small video file, cut from a larger one ?

  9 mars 2024, par Giuliano Oliveri

  I'm trying to cut video files into smaller chunks. (each one being one word said in the video, so they're not all of equal size)

  


  I've tried a lot of different approaches to try to be as efficient as possible, but I can't get the runtime to be under 2/3rd of the original video length. That's an issue because I'm trying to process 400+ hours of video.

  


  Is there a more efficient way to do this ? Or am I doomed to run this for weeks ?

  


  Here is the command for my best attempt so far

  


  ffmpeg -hwaccel cuda -hwaccel_output_format cuda -ss start_timestamp -t to_timestamp -i file_name -vf "fps=30,scale_cuda=1280:720" -c:v h264_nvenc -y output_file


  


  Note that the machine running the code has a 4090
This command is then executed via python, which gives it the right timestamps and file paths for each smaller clip in a for loop

  


  I think it's wasting a lot of time calling a new process each time, however I haven't been able to get better results with a split filter ; but here's the ffmpeg-python code for that attempt :

  


  Creation of the stream :

  


  inp = (
    ffmpeg
    .input(file_name, hwaccel="cuda", hwaccel_output_format="cuda")
    .filter("fps",fps=30)
    .filter('scale_cuda', '1280','720')
    .filter_multi_output('split')
)


  


  Which then gets called in a for loop

  


  (
    ffmpeg
    .filter(inp, 'trim', start=row[1]['start'], end=row[1]['end'])
    .filter('setpts', 'PTS-STARTPTS')
    .output(output_file,vcodec='h264_nvenc')
    .run()
)


  


• Is there an efficient way to use ffmpeg to perform a large quantity of cuts from a single file ?

  16 mars 2024, par Giuliano Oliveri

  I'm trying to cut video files into smaller chunks. (each one being one word said in the video, so they're not all of equal size)

  


  I've tried a lot of different approaches to try to be as efficient as possible, but I can't get the runtime to be under 2/3rd of the original video length. That's an issue because I'm trying to process 400+ hours of video.

  


  Is there a more efficient way to do this ? Or am I doomed to run this for weeks ?

  


  Here is the command for my best attempt so far

  


  ffmpeg -hwaccel cuda -hwaccel_output_format cuda -ss start_timestamp -t to_timestamp -i file_name -vf "fps=30,scale_cuda=1280:720" -c:v h264_nvenc -y output_file


  


  Note that the machine running the code has a 4090
This command is then executed via python, which gives it the right timestamps and file paths for each smaller clip in a for loop

  


  I think it's wasting a lot of time calling a new process each time, however I haven't been able to get better results with a split filter ; but here's the ffmpeg-python code for that attempt :

  


  Creation of the stream :

  


  inp = (
    ffmpeg
    .input(file_name, hwaccel="cuda", hwaccel_output_format="cuda")
    .filter("fps",fps=30)
    .filter('scale_cuda', '1280','720')
    .filter_multi_output('split')
)


  


  Which then gets called in a for loop

  


  (
    ffmpeg
    .filter(inp, 'trim', start=row[1]['start'], end=row[1]['end'])
    .filter('setpts', 'PTS-STARTPTS')
    .output(output_file,vcodec='h264_nvenc')
    .run()
)


  


• Splitting audio tracks with incorrect length - FFMPEG

  26 mars 2018, par channae

  Version : com.writingminds:FFmpegAndroid:0.3.2

  I have an audio file with length 43 seconds. And I wrote an algorithm to split at each 10 seconds mark where a word ends (For this I used IBM Watson to get ending timestamp). So cropping duration is always around 10 seconds to 11 seconds. Of course except the 5th one. I have printed my commands so that you will understand my use-case better.

  System.out: Split Command: -y -i /storage/emulated/0/AudioClipsForSpeakerRecognition/merge.wav -ss 00:00:00.000 -codec copy -t 00:00:10.010 /storage/emulated/0/AudioClipsForSpeakerRecognition/segment_1.wav
  
  
  
  System.out: Split Command: -y -i /storage/emulated/0/AudioClipsForSpeakerRecognition/merge.wav -ss 00:00:10.010 -codec copy -t 00:00:21.090 /storage/emulated/0/AudioClipsForSpeakerRecognition/segment_2.wav
  
  
  
  System.out: Split Command: -y -i /storage/emulated/0/AudioClipsForSpeakerRecognition/merge.wav -ss 00:00:21.090 -codec copy -t 00:00:30.480 /storage/emulated/0/AudioClipsForSpeakerRecognition/segment_3.wav
  
  
  
  System.out: Split Command: -y -i /storage/emulated/0/AudioClipsForSpeakerRecognition/merge.wav -ss 00:00:30.480 -codec copy -t 00:00:40.120 /storage/emulated/0/AudioClipsForSpeakerRecognition/segment_4.wav
  
  
  
  System.out: Split Command: -y -i /storage/emulated/0/AudioClipsForSpeakerRecognition/merge.wav -ss 00:00:40.120 -codec copy -t 00:00:43.000 /storage/emulated/0/AudioClipsForSpeakerRecognition/segment_5.wav

  However when playing all cropped audio files I noticed segment_1 is about 10 seconds and segment_2 is about 20 seconds etc. Therefore some of the audio parts belong to segment_1 also available in segment 2 etc etc. Why is this happening ?

  Appreciate your response.