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• aacenc : implement Intensity Stereo encoding support

  2 juillet 2015, par Rostislav Pehlivanov

  aacenc : implement Intensity Stereo encoding support
  This commit implements intensity stereo coding support
  
  to the native aac encoder. This is a way to increase the efficiency
  
  of the encoder by zeroing the right channel’s spectral coefficients
  
  (in a channel pair) and rederiving them in the decoder using information
  
  from the scalefactor indices of special band types. This commit
  
  confomrs to the official ISO 13818-7 specifications, although due to
  
  their ambiguity certain deviations have been taken to ensure maximum
  
  sound quality. This commit has been extensively tested and has shown
  
  to not result in audiable audio artifacts unless in extreme cases.
  
  This commit also adds an option, aac_is, which has the value of
  
  0 by default. Intensity Stereo is part of the scalable aac profile
  
  and is thus non-default.
  The way IS coding works is that it rederives the right channel’s
  
  spectral coefficients from the left channel via the scalefactor
  
  index values left in the right channel. Since an entire band’s
  
  spectral coefficients do not need to be coded, the encoder’s
  
  efficiency jumps up and it unzeroes some high frequency values
  
  which it previously did not have enough bits to encode. That way
  
  less information is lost than the information lost by rederiving
  
  the spectral coefficients with some error. This is why the
  
  filesize of files encoded with IS do not decrease significantly.
  
  Users wishing that IS coding should reduce filesize are expected
  
  to reduce their encoding bitrates appropriately.
  This is V2 of the commit. The old version did not mark ms_mask as
  
  0 since M/S and IS coding are incompactible, which resulted in
  
  distortions with M/S coding enabled. This version also improves
  
  phase detection by measuring it for every spectral coefficient in
  
  the band and using a simple majority rule to determine whether the
  
  coefficients are in or out of phase. Also, the energy values per
  
  spectral coefficient were changed as to reflect the
  
  official specifications.
  Reviewed-by : Claudio Freire <klaussfreire@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michaelni@gmx.at>
  

  • [DH] libavcodec/aaccoder.c
  • [DH] libavcodec/aacenc.c
  • [DH] libavcodec/aacenc.h

• Convert video to HLS in iOS app without triggering GPL (FFmpegKit alternative ?) [closed]

  7 juillet, par Aziz Bibitov

  I'm building an iOS app in Swift that needs to convert local video files to HLS format (.m3u8). Initially, I used the ffmpeg-kit-ios-full-gpl package from FFmpegKit, which works well. However, since this build includes GPL-licensed components (such as libx264), I'm concerned that using it would require my app to be released under the GPL, which is not compatible with App Store distribution.

  


  That said, my needs are fairly basic : I only need to convert H.264 .mp4 video files into HLS format.

  


  My Questions :

  


  

  1. Is there a safe way to use FFmpegKit—such as the full-libarary-lgpl variant—that guarantees no GPL components are used for this task ?

  


  2. Are there any iOS-native or third-party tools that can reliably convert H.264 .mp4 video files to HLS on-device without introducing GPL concerns ?

  


  3. Is using Apple’s AVAssetExportSession a viable alternative for exporting to HLS ? I haven't found much official documentation about using it for HLS output.

  


  


  Any guidance on how to perform HLS conversion in an App Store–safe (non-GPL) way would be much appreciated.

  


• FFMPEG via PHP - no thumbnail or log output generated

  10 octobre 2018, par Utkanos

  I’m trying to get my head around command line syntax in the form of FFMPEG via PHP.

  I’ve successfully installed it and I can use it fine, until I try to :

  • run background tasks
  • generate output to a log

  This code attempts to create a thumbnail from a video. And it does, if I make it synchrnous, i.e. remove everything from onwards code>....

  shell_exec($i = 'ffmpeg -y -i '.$fp.' -ss '.$secs.' -vframes 1 '.$dirs_path.'/thumb.png  null >/dev/null 2>/ffmpeg.txt &');

  I’ve derived the background part of this command from this page on the official FFMPEG site.

  ($secs is an integer denoting a seconds point within the video duration, and $fp is the save path of the video. Both are valid.)

  So the thumb doesn’t get generated, and there’s no ffmpeg.txt created, either in the place where the script runs, or in the server root or anything. I may be looking in the wrong place... I’m unsure what all this is relative to.

  Any help appreciated.