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• 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];

• lavu : add an API function to return the Libav version string

  2 juillet 2015, par wm4

  lavu : add an API function to return the Libav version string
  This returns something like "v12_dev0-1332-g333a27c". This is much more
  
  useful than the individual library versions, of which there are too
  
  many, and which are very hard to map back to releases or git commits.
  Signed-off-by : Janne Grunau <janne-libav@jannau.net>
  

  • [DH] .gitignore
  • [DH] Makefile
  • [DH] cmdutils.c
  • [DH] doc/APIchanges
  • [DH] libavutil/avutil.h
  • [DH] libavutil/utils.c

• Convert an h264 byte string to OpenCV images

  24 mars 2017, par Fred Dufresne

  In Python, how do I convert an h264 byte string to images OpenCV can read, only keeping the latest image ?

  Long version :

  Hi everyone.

  Working in Python, I’m trying to get the output from adb screenrecord piped in a way that allows me to capture a frame whenever I need it and use it with OpenCV. As I understand, I need to constantly read the stream because it’s h264.

  I’ve tried multiple things to get it working and concluded that I needed to ask for specific help.

  The following gets me the stream I need and works very well when I print stream.stdout.read(n).

  import subprocess as sp
  
  
  
  adbCmd = ['adb', 'exec-out', 'screenrecord', '--output-format=h264', '-']
  
  stream = sp.Popen(adbCmd, stdout = sp.PIPE, universal_newlines = True)

  Universal newlines was necessary to get it to work on Windows.

  Doing :

  sp.call(['ffplay', '-'], stdin = stream.stdout, universal_newlines = True)

  Works.

  The problem is I am now trying to use ffmpeg to take the input h264 stream and output as many frames as possible, overwriting the last frame if needed.

  ffmpegCmd = ['ffmpeg', '-f', 'image2pipe', '-pix_fmt', 'bgr24', '-vcodec', 'h264', 'fps=30', '-']
  
  ffmpeg = sp.Popen(ffmpegCmd, stdin = stream.stdout, stdout = sp.PIPE, universal_newlines = True)

  This is what I think should be used, but I always get the error "Output file #0 does not contain any stream".

  Edit :

  Final Answer

  Turns out the universal_newlines option was ruining the line endings and gradually corrupting the output. Also, the ffmpeg command was wrong, see LordNeckbeard’s answer.

  Here’s the correct ffmpeg command to achieve what was used :

  ffmpegCmd = ['ffmpeg', '-i', '-', '-f', 'rawvideo', '-vcodec', 'bmp', '-vf', 'fps=5', '-']
  
  ffmpeg = sp.Popen(ffmpegCmd, stdin = stream.stdout, stdout = sp.PIPE)

  And then to convert the result into an OpenCV image, you do the following :

  fileSizeBytes = ffmpeg.stdout.read(6)
  
  fileSize = 0
  
  for i in xrange(4):
  
      fileSize += fileSizeBytes[i + 2] * 256 ** i
  
  bmpData = fileSizeBytes + ffmpeg.stdout.read(fileSize - 6)
  
  image = cv2.imdecode(np.fromstring(bmpData, dtype = np.uint8), 1)

  This will get every single frame of a stream as an OpenCV image.