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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

• avcodec/bitstream : Consistently treat symbol as VLC_TYPE

  26 octobre 2020, par Andreas Rheinhardt

  avcodec/bitstream : Consistently treat symbol as VLC_TYPE
  If a static VLC table gets initialized a second time (or concurrently by
  
  two threads) and if said VLC table uses symbols that have the sign bit
  
  of VLC_TYPE (a typedef for int16_t) set, initializing the VLC fails. The
  
  reason is that the type of the symbol in the temporary array is an
  
  uint16_t and so comparing it to the symbol read from the VLC table will
  
  fail, because only the lower 16bits coincide. Said failure triggers an
  
  assert.
  Reviewed-by : Lynne <dev@lynne.ee>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@gmail.com>
  

  • [DH] libavcodec/bitstream.c

• FFmpeg - Save %{pts\:hms} in %variable% for saving as environment variable

  29 novembre 2020, par cmd_kevin

  After closing a video in ffplay I want that the last timestamp will saved as a value of an environment variable.

  


  To show the current timestamp in the playback window, I can use :

  


  ffplay -vf "drawtext=text='%{pts\:hms}'" input.mp4


  


  So there is a variable (%{pts\:hms}) for my purposes.

  


  To change the value of a variable (in my case %variable01%), I used :

  


  SET variable01=value


  


  To change the environment variable with %variable01%, I used : SETX environment_variable_01 %variable01%.

  


  My problem is that I can't use %{pts\:hms} to define %variable01% and echo %{pts\:hms} or SETX environment_variable_01 %{pts\:hms} didn't work.

  


  So I'm trying to transfer the %{pts\:hms} value to %variable01% but all of my attempts failed.

  


  What can I do to solve my problem ?

  


  I want this environment value to continue a video at the timestamp I closed ffplay and the command prompt.

  


  Edit1 : I have used search facility but I didn't find an answer, especially to this specific syntax with only one percent sign %{pts\:hms}.

  


  Here's my reproducible example :
ffplay -vf "drawtext=text='%{pts\:hms}'" input.mp4 & echo %{pts:hms}
Answer : %{pts\:hms}.

  


  I also tried :

  


  ffplay -vf "drawtext=text='%{pts\:hms}'" input.mp4 & SET variable01=%{pts\:hms}


  


  but the answer with

  


  echo %variable01%


  


  is

  


  %{pts\:hms}.


  


  Changing to %{pts\:hms}%didn't work too. The answer of echo is %{pts\:hms}%.