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• How to convert MP4 to MP3 in VLC using Command-Prompt ?

  9 juillet 2016, par user6472523

  I have close to 0 programming experience but would like to figure out how to do this and have been trying to figure out how to do this for awhile. I’m getting very frustrated - wish I could understand it. I’m trying to convert a bunch of MP4 files to MP3 files. I would like to keep the original file and just spit out a bunch of MP3 files with same name as the original file.

  From here : https://wiki.videolan.org/How_to_Batch_Encode/

  Apparently, all you need to do is use this code in the Command-Prompt. I have never really used the Command-Prompt before so no idea what to do.

  FOR /R %%G IN (*.m4a) DO (CALL :SUB_VLC "%%G")
  
  FOR /R %%G IN (*.m4a.mp*) DO (CALL :SUB_RENAME "%%G")
  
  GOTO :eof
  
  
  
  :SUB_VLC
  
   SET _firstbit=%1
  
   SET _qt="
  
   CALL SET _newnm=%%_firstbit:%_qt%=%%
  
   SET _commanm=%_newnm:,=_COMMA_%
  
   REM echo %_commanm%
  
   CALL "C:\Program Files\VideoLAN\VLC\vlc" -I dummy -vvv %1 --sout=#transcode{acodec="mpga",ab="512","channels=2",samplerate="44100"}:standard{access="file",mux="mpeg1",dst="%_commanm%.mp3"} vlc://quit
  
  GOTO :eof
  
  
  
  :SUB_RENAME
  
   SET _origfnm=%1
  
   SET _endbit=%_origfnm:*.m4a=%
  
   CALL SET _newfilenm=%%_origfnm:.m4a%_endbit%=.mp3%%
  
   SET _newfilenm=%_newfilenm:_COMMA_=,%
  
   COPY %1 %_newfilenm%
  
   DEL %1
  
  GOTO :eof
  
  
  
  :eof

  1. So far I changed the directory in the Command-Prompt to the
     folder where the MP4 files are located.
  2. In the code, I’ve changed all mention of .m4a to .mp4.
  3. I’ve change mpga to mp3.
  4. I’ve changed "C :\Program Files\VideoLAN\VLC\vlc" to where my vlc program
     is located.

  What else do I need to do ? And what do all the %% mean in the code ?

  Thank you so much !

• hwcontext_vaapi : Do not assume that sw_format is transferable

  24 novembre 2017, par Mark Thompson

  hwcontext_vaapi : Do not assume that sw_format is transferable
  Drivers can support a format for surfaces without also supporting it for
  
  images, so we can't assume that sw_format is usable for transfer.  This
  
  would previously hit an assert in cases where it isn't.
  

  • [DH] libavutil/hwcontext_vaapi.c

• Hardware decoding using vaapi [on hold]

  15 août 2017, par Orient

  I am trying to replicate hardware decoding using vaapi. My ultimate goal is to get an OpenGL texture wich I whant to get from a vasurface buffer.

  I took as a base https://github.com/gbeauchesne/ffvademo/tree/master/src
  which looks less intimidating than other examples. My initial understanding was that packets were somehow rendered to surfaces (render targets) and at the same time got converted. But it looks like the loop after some nested calls boils down to avcodec_decode_video2 (app_decode_frame -> ffva_decoder_get_frame -> decoder_get_frame -> decoder_run -> decode_packet -> avcodec_decode_video2), which in turn would call codec->decode. So it resembles the way decoding is done on CPU.

  Could anybody explain why this whoud be considered hw decoding ?