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• Unable to use Multithread for librosa melspectrogram

  15 avril 2019, par Raven Cheuk

  I have over 1000 audio files (it’s just a initial development, in the future, there will be even more audio files), and would like to convert them to melspectrogram.

  Since my workstation has a Intel® Xeon® Processor E5-2698 v3, which has 32 threads, I would like to use multithread to do my job.

  My code

  import os
  
  import librosa
  
  from librosa.display import specshow
  
  from natsort import natsorted
  
  import numpy as np
  
  import sys 
  
  # Libraries for multi thread
  
  from multiprocessing.dummy import Pool as ThreadPool
  
  import subprocess
  
  pool = ThreadPool(20) 
  
  
  
  songlist = os.listdir('../opensmile/devset_2015/')
  
  songlist= natsorted(songlist)
  
  
  
  def get_spectrogram(song):
  
      print("start")
  
      y, sr = librosa.load('../opensmile/devset_2015/' + song)
  
  
  
      ## Add some function to cut y
  
      y_list = y
  
      ##
  
  
  
      for i, y_i in enumerate([y_list]): # can remove for loop if no audio is cut
  
          S = librosa.feature.melspectrogram(y=y, sr=sr, n_mels=128,fmax=8000)
  
          try:
  
              np.save('./Test/' + song + '/' + str(i), S)
  
          except:
  
              os.makedirs('./Test/' + song)
  
              np.save('./Test/' + song + '/' + str(i), S)
  
          print("done saving")
  
  
  
  pool.map(get_spectrogram, songlist)

  My Problem

  However, my script freezes after finished the first conversion.

  To debug what’s going on, I commented out S = librosa.feature.melspectrogram(y=y, sr=sr, n_mels=128,fmax=8000) and replace it by S=0.
  Then the multi-thread code works fine.

  What’s wrong with the librosa.feature.melspectrogram function ? Does it not support multi-thread ? Or is it a problem of ffmpeg ? (When using librosa, it asks me to install ffmpeg before.)

• How can i use ffmpeg to add voice note to another mp3 at specific time , let everything play without reducing the original mp3

  29 juin 2020, par Adike maduabuchi

  I have used some code which does not give me what I want, I used PHP shell to execute the code

  


               $var = 'ffmpeg -y -i ' . $voice_note_tag . ' -i ' . $original_music_path . '  -filter_complex "[0]asplit[a][b]; [a]atrim=duration=' . $time_come_vioce . ',volume=\'1-max(0*(t-1),0)\':eval=frame[pre];  [b]atrim=start=' . $time_come_vioce . ',asetpts=PTS-STARTPTS[song];  [song][1]amix=inputs=2:duration=first:dropout_transition=2[post]; [pre][post]concat=n=2:v=0:a=1[mixed]"  -map "[mixed]" ' . $output . ' 2>&1';
                            shell_exec($var);


  


• How should I use the dash (not webm_dash_manifest !) format in ffmpeg ?

  26 mars 2018, par Alton Patrick

  FFmpeg has a format named "dash" :

  > ffmpeg -formats
  
  ...
  
    E dash            DASH Muxer
  
  ...

  This presumably corresponds to the code in libavformat/dashenc.c.

  I can find a number of items on the web about how to use the WebM DASH Manifest format, but nothing at all about this other DASH format.

  Can someone point me to documentation or examples that use the "DASH Muxer" either from the command line or API ?