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• avcodec/smacker : Use unsigned for prediction values

  26 juin 2020, par Andreas Rheinhardt

  avcodec/smacker : Use unsigned for prediction values
  Up until now, the Smacker decoder has pretended that the prediction
  
  values are signed in code like 'pred[0] += (unsigned)sign_extend(val, 16)'
  
  (the cast has been added to this code later to fix undefined behaviour).
  
  This has been even done in case the PCM format is u8.
  Yet in case of 8/16 bit samples, only the lower 8/16 bit of the predicition
  
  values are ever used, so one can just as well just use unsigned and
  
  remove the sign extensions. This is what this commit does.
  For GCC 9 the time for one call to smka_decode_frame() for the sample from
  
  ticket #2425 decreased from 1709043 to 1693619 decicycles ; for Clang 9
  
  it went up from 1355273 to 1369089 decicycles.
  Reviewed-by : Paul B Mahol <onemda@gmail.com>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/smacker.c

• qt-faststart : Avoid unintentionally sign extending BE_32

  28 février 2014, par Martin Storsjö

  qt-faststart : Avoid unintentionally sign extending BE_32
  Without this cast, the BE_32() expression is sign extended when
  
  assigned to an uint64_t, since the uint8_t|uint8_t expression
  
  is promoted to an int.
  Also avoid undefined behaviour when left shifting an uint8_t
  
  by 24 by casting it to an uint32_t explicitly before shifting.
  Based on a patch by Michael Niedermayer.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DBH] tools/qt-faststart.c

• ffmpeg - Convert files but keep Same Date Modification as Original ?

  9 septembre 2021, par user5894146

  So I want to start with that ffmpeg and powershell isn't really my strength but I have been using the following powershell command to convert every .flac file in a certain directory to a 320K file.

  


  dir *.flac | foreach {ffmpeg -i $_.FullName -c:v copy  -b:a 320k  $_.FullName.Replace('flac', 'mp3')}


  


  This works exactly how I want to without any album art being transcoded but I want to incorporate a way so that the new .mp3 files that are created have the SAME DATE MODIFICATION value of the .flac files. Is something like this even possible ?

  


  audio_ex.flac = Date Modification: 1/1/2010
audio_ex.mp3 = Date Modification: 9/8/2021


  


  should be instead

  


  audio_ex.flac = Date Modification: 1/1/2010
audio_ex.mp3 = Date Modification: 1/1/2010


  


  I have a folder of 6K files and want each original date modified to match the newly created files so if I can do the above command and also have the date mod time match within one execution, that would be ideal.

  


  I thought of manually changing each files mod time using 3rd party tools but it will be too time consuming.