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• avcodec/vbnenc : Add AV_CODEC_CAP_DR1

  12 avril 2022, par Andreas Rheinhardt

  avcodec/vbnenc : Add AV_CODEC_CAP_DR1
  This encoder uses ff_get_encode_buffer().
  Reviewed-by : Marton Balint <cus@passwd.hu>
  
  Signed-off-by : Andreas Rheinhardt <andreas.rheinhardt@outlook.com>
  

  • [DH] libavcodec/vbnenc.c

• avcodec/x86/vvc/vvcdsp_init : add put prototypes

  17 avril 2024, par Wu Jianhua

  avcodec/x86/vvc/vvcdsp_init : add put prototypes
  When we used the —disable-ssse3 —disable-optimizations options,
  
  the compiler would not skip the MC_LINKS like the compilation that
  
  enabled the optimization, so it would fail to find the function
  
  prototypes. Hence, this commit uses the same way to add prototypes
  
  for the functions as HEVC DSP.
  Signed-off-by : Wu Jianhua <toqsxw@outlook.com>
  

  • [DH] libavcodec/x86/vvc/vvcdsp_init.c

• avutil/mathematics : speed up av_gcd by using Stein’s binary GCD algorithm

  11 octobre 2015, par Ganesh Ajjanagadde

  avutil/mathematics : speed up av_gcd by using Stein’s binary GCD algorithm
  This uses Stein’s binary GCD algorithm :
  
  https://en.wikipedia.org/wiki/Binary_GCD_algorithm
  
  to get a roughly 4x speedup over Euclidean GCD on standard architectures
  
  with a compiler intrinsic for ctzll, and a roughly 2x speedup otherwise.
  
  At the moment, the compiler intrinsic is used on GCC and Clang due to
  
  its easy availability.
  Quick note regarding overflow : yes, subtractions on int64_t can, but the
  
  llabs takes care of that. The llabs is also guaranteed to be safe, with
  
  no annoying INT64_MIN business since INT64_MIN being a power of 2, is
  
  shifted down before being sent to llabs.
  The binary GCD needs ff_ctzll, an extension of ff_ctz for long long (int64_t). On
  
  GCC, this is provided by a built-in. On Microsoft, there is a
  
  BitScanForward64 analog of BitScanForward that should work ; but I can’t confirm.
  
  Apparently it is not available on 32 bit builds ; so this may or may not
  
  work correctly. On Intel, per the documentation there is only an
  
  intrinsic for _bit_scan_forward and people have posted on forums
  
  regarding _bit_scan_forward64, but often their documentation is
  
  woeful. Again, I don’t have it, so I can’t test.
  As such, to be safe, for now only the GCC/Clang intrinsic is added, the rest
  
  use a compiled version based on the De-Bruijn method of Leiserson et al :
  
  http://supertech.csail.mit.edu/papers/debruijn.pdf.
  Tested with FATE, sample benchmark (x86-64, GCC 5.2.0, Haswell)
  
  with a START_TIMER and STOP_TIMER in libavutil/rationsl.c, followed by a
  
  make fate.
  aac-am00_88.err :
  
  builtin :
  
  714 decicycles in av_gcd,    4095 runs,      1 skips
  de-bruijn :
  
  1440 decicycles in av_gcd,    4096 runs,      0 skips
  previous :
  
  2889 decicycles in av_gcd,    4096 runs,      0 skips
  Signed-off-by : Ganesh Ajjanagadde <gajjanagadde@gmail.com>
  
  Signed-off-by : Michael Niedermayer <michael@niedermayer.cc>
  

  • [DH] libavutil/intmath.h
  • [DH] libavutil/mathematics.c