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• Transcode HLS Segments individually using FFMPEG

  27 mai 2013, par rayh

  I am recording a continuous, live stream to a high-bitrate HLS stream. I then want to asynchronously transcode this to different formats/bitrates. I have this working, mostly, except audio artefacts are appearing between each segment (gaps and pops).

  Here is an example ffmpeg command line :

  ffmpeg -threads 1 -nostdin -loglevel verbose \
  
     -nostdin -y -i input.ts -c:a libfdk_aac \
  
     -ac 2 -b:a 64k -y -metadata -vn output.ts

  Inspecting an example sound file shows that there is a gap at the end of the audio :

  

  And the start of the file looks suspiciously attenuated (although this may not be an issue) :

  

  My suspicion is that these artefacts are happening because transcoding are occurring without the context of the stream as a whole.

  Any ideas on how to convince FFMPEG to produce audio that will fit back into a HLS stream ?

  ** UPDATE 1 **

  Here are the start/end of the original segment. As you can see, the start still appears the same, but the end is cleanly ended at 30s. I expect some degree of padding with lossy encoding, but I there is some way that HLS manages to do gapless playback (is this related to iTunes method with custom metadata ?)

  
  

  ** UPDATED 2 **

  So, I converted both the original (128k aac in MPEG2 TS) and the transcoded (64k aac in aac/adts container) to WAV and put the two side-by-side. This is the result :

  
  

  I'm not sure if this is representative of how a client will play it back, but it seems a bit odd that decoding the transcoded one introduces a gap at the start and makes the segment longer. Given they are both lossy encoding, I would have expected padding to be equally present in both (if at all).

  ** UPDATE 3 **

  According to http://en.wikipedia.org/wiki/Gapless_playback - Only a handful of encoders support gapless - for MP3, I've switched to lame in ffmpeg, and the problem, so far, appears to have gone.

  For AAC (see http://en.wikipedia.org/wiki/FAAC), I have tried libfaac (as opposed to libfdk_aac) and it also seems to produce gapless audio. However, the quality of the latter isn't that great and I'd rather use libfdk_aac is possible.

• ffmpeg.so in PHP exec converting and no return

  13 juin 2015, par Tom

  I have seen many threads, but none working ones, so this is my issue :

  I have server installed ffmpeg (ffmpeg-php version 0.7.0, PHP Version 5.4.41) Linux CentOS 6 64bit :

  Using PHP :

  exec('/usr/lib64/php/modules/ffmpeg.so -i test.mp4 testdone.avi',$out,$ret);

  or

  exec('/usr/lib64/php/modules/ffmpeg.so -i /var/www/html/test.mp4 /var/www/html/testdone.avi',$out,$ret);

  or

  exec('/usr/lib64/php/modules/ffmpeg.so -i /var/www/html/test.mp4 /var/www/html/testdone.avi'.' 2>&1',$out,$ret);  

  the ffmpeg is actually found, but always returns : array(0) { } int(11) and with 2>&1 returns array(0) { } int(139) and does not return anything else like testdone.avi in the directory or -version (in the directory). Directories /var/www/html/ are set to 777.

  Thank you, should I hire someone to fix this or am I missing something in PHP.

• FFmpeg os.system commands not working but work in Terminal

  28 janvier 2020, par Oscar Dolloway

  I’ve downloaded ffmpeg through the website and ran some commands through the terminal to confirm its install.

  when running the command ’ffmpeg’ in the Terminal it returns

   ffmpeg version 4.2.2 Copyright (c) 2000-2019 the FFmpeg 
  
   developers
  
   built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)

  if i type into Python

  import os
  
  os.system ('ffmpeg')

  it returns

   os.system ('ffmpeg')
  
   sh: ffmpeg: command not found
  
   Out[25]: 32512

  any ideas ?

  Solution :

   ffmpeg = '/bin/ffmpeg' #path to the binary file
  
  
  
   os.system(ffmpeg)

  Output :

  os.system (ffmpeg)
  
  ffmpeg version 4.2.2 Copyright (c) 2000-2019 the FFmpeg developers
  
  built with Apple LLVM version 10.0.0 (clang-1000.11.45.5)