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• lavc/opusdsp : RISC-V V (512-bit) postfilter

  5 octobre 2022, par Rémi Denis-Courmont

  lavc/opusdsp : RISC-V V (512-bit) postfilter
  This adds a variant of the postfilter for use with 512-bit vectors.
  
  Half a vector is enough to perform the scalar product. Normally a whole
  
  vector would be used anyhow. Indeed fractional multiplers are no faster
  
  than the unit multipler.
  But in this particular function, a full vector makes up 16 samples,
  
  which would be loaded at each iteration of the outer loop. The minimum
  
  guaranteed CELT postfilter period is only 15. Accounting for the edges,
  
  we can only safely preload up to 13 samples.
  The fractional multipler is thus used to cap the selected vector length
  
  to a safe value of 8 elements or 256 bits.
  Likewise, we have the 1024-bit variant with the quarter multipler. In
  
  theory, a 2048-bit one would be possible with the eigth multipler, but
  
  that length is not even defined in the specifications as of yet, nor is
  
  it supported by any emulator - forget actual hardware.
  

  • [DH] libavcodec/riscv/opusdsp_init.c
  • [DH] libavcodec/riscv/opusdsp_rvv.S

• libavcodec/mpeg12dec : Check input for minimal frame size

  4 septembre 2019, par Michael Niedermayer

  libavcodec/mpeg12dec : Check input for minimal frame size
  Fixes : Timeout (35sec -> 6sec)
  
  Fixes : 16901/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEGVIDEO_fuzzer-5729024726269952
  
  Fixes : 16901/clusterfuzz-testcase-minimized-ffmpeg_AV_CODEC_ID_MPEGVIDEO_fuzzer-5642388592132096
  Found-by : continuous fuzzing process https://github.com/google/oss-fuzz/tree/master/projects/ffmpeg
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavcodec/mpeg12dec.c

• Finding a minimal configuration for ffmpeg

  28 novembre 2022, par Clemens3000

  i am currently developing a video player for Windows and Mac using JUCE and FFmpeg. For this i want to include FFmpeg as a shared library and compile it myself in a minimal configuration to get rid of features and dependencies i don't need. This turns out to be quite difficult, since FFmpeg has a HUGE load of dependencies. And i am pretty new to this compiling game.

  


  Of course i checked all the options for configuration, but there is so many and don't have much knowledge about what all the options actually do. Some are obvious, but many are not.

  


  The minimal configuration i am looking for should enable to playback videofiles encoded with h.264 and it should be LGPL compliant. So just decoding, no encoding.

  


  What i did :

  


  

  • i installed some of the dependencies i might need via macports (under /opt/local)

  


  • i downloaded ffmpeg source code, played around with the configure options and compiled it

  


  • i managed to build my app and it even runs

  


  • i created a configuration with "—disable_everything" and then tried to add features one after another until i build something that works. But that's like finding a needle in the haystack.

  


  


  For Mac my first attempt for this is :
./configure --disable-everything --prefix='../../osx_arm' --install-name-dir='@executable_path/../libs' --extra-ldflags=-Wl,-rpath,'@executable_path/../libs' --enable-version3 --enable-shared --disable-static --enable-swscale --enable-avfilter --enable-libfdk-aac --enable-audiotoolbox --enable-videotoolbox --enable-pthreads --cc=/usr/bin/clang --extra-ldflags=-L/opt/local/lib

  


  I can compile and link my program and as i expected I cannot do much more, which is totally fine for now.

  


  My questions are now :

  


  


  1. How can i find out which configure options are essential to enable simple playback ? How do i find out which options can be discarded ?

     


  


  2. If i run otool on the resulting libs in my current minimal build i still get some dependencies :

     


  


  


  otool -L ../../osx_arm/lib/libavcodec.59.37.100.dylib  ../../osx_arm/lib/libavcodec.59.37.100.dylib: @executable_path/../libs/libavcodec.59.dylib (compatibility version 59.0.0, current version 59.37.100) @executable_path/../libs/libavutil.57.dylib (compatibility version 57.0.0, current version 57.28.100) /opt/local/lib/libiconv.2.dylib (compatibility version 9.0.0, current version 9.1.0) /usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1292.100.5) /System/Library/Frameworks/VideoToolbox.framework/Versions/A/VideoToolbox (compatibility version 1.0.0, current version 1.0.0) /opt/local/lib/libX11.6.dylib (compatibility version 11.0.0, current version 11.0.0) /System/Library/Frameworks/CoreFoundation.framework/Versions/A/CoreFoundation (compatibility version 150.0.0, current version 1775.118.101) /System/Library/Frameworks/CoreMedia.framework/Versions/A/CoreMedia (compatibility version 1.0.0, current version 1.0.0) /System/Library/Frameworks/CoreVideo.framework/Versions/A/CoreVideo (compatibility version 1.2.0, current version 1.5.0) /System/Library/Frameworks/CoreServices.framework/Versions/A/CoreServices (compatibility version 1.0.0, current version 1122.33.0)

  


  Why does FFmpeg actually need libiconv or libX11 ? I believe those don't have to do much with video/audio, right ? Well, I guess FFmpeg needs them anyway...So do i need to compile them myself to and add them to my Application ? I guess later i'll have even more dependencies.

  


  

  3. Any other tips on how to accomplish what i want ?