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• Something missing during transcoding audio-only pieces from FLV format to AAC format ?

  21 octobre 2012, par MaiTiano

  I have ten consecutive flv pieces cut from a song in flv format. Each flv piece has about 10 seconds long.

  After I transcode these flv format audio piece into wav format by ffmpeg, I drag the new 10 wav file into foobar player and play them automatically(one-by-one played automatically). I found there is no "broken/pause" feeling in during switching from the end part of previous wav file to the start part of the next wav file.

  However, after I transcode these flv format audio piece into AAC format by ffmpeg, and do the similar listening test in the foobar player, I can hear/feel obvious breakpoint when file changing.

  Is it possible for ffmpeg to miss some audio signal during flv->aac transcoding ? Because, the transcoded aac files are supposed to be played one-by-one contiguously just like there is one file playing, in other words, there should not be the breakpoint feeling happened between two consecutive file playing !

  Any advices ? Many thanks.

• Returning shell_exec as string PHP detecting BPM with soundtouch/soundstrech

  23 janvier 2016, par Jeff

  I am working on a php function used to upload a .wav to server (along with converting to mp3 and creating waveform image png) , and within the function I would like it to use soundtouch / soundstrech to detect the B.P.M. (Beats Per Minute). I know it will not be the most accurate but for my purposes it will be all I need.

  I was able to get the B.P.M. of a .wav file using soundtouch / soundstrech along with ffmpeg within a test.php file using deven’s php-bpm-detect wrapper But When I try to integrate it within my PHP function it returns the B.P.M. as zero.

  I am wondering if there is a simpler way to get the bpm as a string from the following shell exec without having to use a separate php library ?

  I would like to perform this and have it return as a string :

  $song_bpm = shell_exec('soundstretch ' . $file_path . ' -bpm');

  test.php (This works and returns the proper bpm :)

  <?php
  
  require "class.bpm.php";
  
  $wavfile = "38a2819c20.wav";
  
  $bpm_detect = new bpm_detect($wavfile);  
  
  $test = $bpm_detect->detectBPM();
  
  echo ' bpm of ' . $wavfile . ' is: ' . $test . ' ';
  
  ?>

  PHP Function : (returns bpm as zero)

  function upload_a_sound($user_id, $file_temp, $file_extn, $name, $uploader, $keywords) {
  
      $timecode = substr(md5(time()), 0, 10);
  
      $mp3name = 'beats/' . $timecode . '.mp3';
  
      $file_path = 'beats/' . $timecode . '.wav';
  
      move_uploaded_file($file_temp, $file_path);
  
      shell_exec('ffmpeg -i ' . $file_path . ' -vn -ar 44100 -ac 2 -ab 192k -f mp3 ' . $mp3name . ''); 
  
      require ('classAudioFile.php'); // This creates a spectogram .png file of .wav
  
      $AF = new AudioFile;
  
      $AF->loadFile($file_path);
  
      $AF->visual_width=200;
  
      $AF->visual_height=200;
  
      $AF->visual_graph_color="#c491db";
  
      $AF->visual_background_color="#000000";
  
      $AF->visual_grid=false;
  
      $AF->visual_border=false;
  
      $AF->visual_graph_mode=0;
  
      $AF->getVisualization ('images/song/' . $timecode . '.png');
  
      $imageloc = 'images/song/' . $timecode . '.png';
  
      require ('class.bpm.php'); //Deseven's class to get bpm, 
  
      $bpm_detect = new bpm_detect($file_path);  
  
      $song_bpm = $bpm_detect->detectBPM(); //when used here this returns 0
  
      mysql_query("INSERT INTO `content` VALUES ('', '', '$name', '$uploader', '$keywords', '$file_path', '$imageloc', '$mp3name', '$song_bpm')"); // I will update this to mysqli soon, for now it works
  
  }

  I also found this which works, but not when I integrate it into my function :

  // create new files, because we don't want to override the old files
  
  $wavFile = $filename . ".wav";
  
  $bpmFile = $filename . ".bpm";
  
  
  
  //convert to wav file with ffmpeg
  
  $exec = "ffmpeg -loglevel quiet -i \"" . $filename . "\" -ar 32000 -ac 1 \"" . $wavFile . "\"";
  
  $output = shell_exec($exec);
  
  
  
  // now execute soundstretch with the newly generated wav file, write the result into a file
  
  $exec = "soundstretch \"" . $wavFile . "\" -bpm  2> " . $bpmFile;
  
  shell_exec($exec);
  
  
  
  // read and parse the file 
  
  $output = file_get_contents($bpmFile);
  
  preg_match_all("!(?:^|(?<=\s))[0-9]*\.?[0-9](?=\s|$)!is", $output, $match);
  
  
  
  // don't forget to delete the new generated files
  
  unlink($wavFile);
  
  unlink($bpmFile);
  
  
  
  // here we have the bpm
  
  echo $match[0][2];

• Mangled output when printing strings from FFProbe STDERR

  9 février 2018, par spikespaz

  I’m trying to make a simple function to wrap around FFProbe, and most of the data can be retrieved correctly.

  The problem is when actually printing the strings to the command line using both Windows Command Prompt and Git Bash for Windows, the output appears mangled and out of order.

  Some songs (specifically the file Imagine Dragons - Hit Parade_ Best of the Dance Music Charts\80 - Beazz - Lime (Extended Mix).flac) are missing metadata. I don’t know why, but the dictionary the function below returns is empty.

  FFProbe outputs its results to stderr which can be piped to subprocess.PIPE, decoded, and parsed. I chose regex for the parsing bit.

  This is a slimmed down version of my code below, for the output take a look at the Github gist.

  #! /usr/bin/env python3
  
  # -*- coding: utf-8 -*-
  
  
  
  import os
  
  
  
  from glob import glob
  
  from re import findall, MULTILINE
  
  from subprocess import Popen, PIPE
  
  
  
  
  
  def glob_from(path, ext):
  
      """Return glob from a directory."""
  
      working_dir = os.getcwd()
  
      os.chdir(path)
  
  
  
      file_paths = glob("**/*." + ext)
  
  
  
      os.chdir(working_dir)
  
  
  
      return file_paths
  
  
  
  
  
  def media_metadata(file_path):
  
      """Use FFPROBE to get information about a media file."""
  
      stderr = Popen(("ffprobe", file_path), shell=True, stderr=PIPE).communicate()[1].decode()
  
  
  
      metadata = {}
  
  
  
      for match in findall(r"(\w+)\s+:\s(.+)$", stderr, MULTILINE):
  
          metadata[match[0].lower()] = match[1]
  
  
  
      return metadata
  
  
  
  
  
  if __name__ == "__main__":
  
      base = "C:/Users/spike/Music/Deezloader"
  
  
  
      for file in glob_from(base, "flac"):
  
          meta = media_metadata(os.path.join(base, file))
  
          title_length = meta.get("title", file) + " - " + meta.get("length", "000")
  
  
  
          print(title_length)

  Output Gist
  Output Raw

  I don’t understand why the output (the strings can be retrieved from the regex pattern effectively, however the output is strangely formatted when printing) appears disordered only when printing to the console using python’s print function. It doesn’t matter how I build the string to print, concatenation, comma-delimited arguments, whatever.

  I end up with the length of the song first, and the song name second but without space between the two. The dash is hanging off the end for some reason. Based on the print statement in the code before, the format should be Title - 000 ({title} - {length}) but the output looks more like 000Title -. Why ?