Recherche avancée

Sur d’autres sites (5800)

• How much the duration of an mp3 file given by Ffprobe is precise ?

  24 septembre 2024, par Julien Larget-Piet

  I have an mp3 file at a sample rate value of 44100, let's name it a.mp3.

  


  So i get the duration of a.mp3 with the following ffprobe command :

  


  ffprobe -v error -show_entries format=duration -of default=noprint_wrappers=1:nokey=1 a.mp3

  


  I get 7.752 seconds.

  


  Because the sample rate is per second, in theory the total amount of samples should be,

  


  44100 * 7.752 = 341863.2

  


  Let's round it to 341863

  


  But using python library ffmpegio with the following code, i get a total amount of sample equal to 340560.

  


  with ffmpegio.open(file, 'ra', blocksize = 16, sample_fmt = 'dbl') as file_opened:

        for i, indata in enumerate(file_opened):

            do some stuff
    print(i * 16)


  


  So there is a non-negligible difference between 341863 and 340560.

  


  I think it comes from the duration value given by Ffmpeg.
What do you thin ?

  


  I search in ffmpegio documentation, but found nothing that trigered my attention :

  


  https://python-ffmpegio.github.io/python-ffmpegio/

  


  Thanks.

  


  Search for answers about the precision of the ffprobe command.

  


• avcodec/flashsv : Avoid deflating data

  11 mars 2022, par Andreas Rheinhardt

  avcodec/flashsv : Avoid deflating data
  Currently priming the zlib decompressor involves compressing
  
  data directly after having decompressed it and decompressing
  
  it again in order to set the "dictionary" and to initialize
  
  the adler32-checksum. Yet this is wasteful and can be simplified
  
  by synthetizing the compressed data via non-compressed blocks.
  This reduced the amount of allocations for the decoding part
  
  of fate-vsynth1-flashsv2, namely from
  
  total heap usage : 9,135 allocs, 9,135 frees, 376,503,427 bytes allocated
  
  to
  
  total heap usage : 2,373 allocs, 2,373 frees, 14,144,083 bytes allocated
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/flashsv.c

• Displaying ffmpeg conversion progress

  29 mars 2014, par Hiigaran

  I'm trying to get an admin function made, in which I want to show a basic status of any file conversion(s) that may or may not be happening upon page load. I'm not entirely sure how to proceed with this, so here is what I have at the moment :

  exec("ffprobe -v quiet -print_format json -show_format '".$fileNameIn.".".$ext."' > /var/www/resources/ffmpegFormat.log");
  
  exec("/ffmpeg/ffmpeg -loglevel 'verbose' -i '".$fileNameIn.".".$ext."' '".$fileNameOut.".flac' null >/dev/null 2>/var/www/resources/ffmpeg.log &",$ffmpegOutput);

  My idea is to use ffprobe to output some information about the file to be converted, then use PHP in some way to read the output file (ffmpegFormat.log) for the total file duration. Once read, ffmpeg begins, while outputting to its own file (ffmpeg.log).

  I'm not looking for anything fancy, like live updates on the progress, so I'm content with simply having a script read the current duration from the last line of the ffmpeg.log file, compare it to the total duration from the ffmpegFormat.log file, and display a percentage only after a page load/refresh.

  I've placed a restriction on conversion to only one file at a time, for the sake of simplifying this progress indicator (and due to a lack of processing power on this computer).

  Assuming there's no simpler way than my idea, how can I do this ?