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• How to speed up ffmpeg video conversion

  22 avril 2018, par user2993497

  ffmpeg -i video.mp4 -c:v libvpx-vp9 -keyint_min 150 -g 150 -tile-columns 4 -frame-parallel 1  -f webm -dash 1 -an -vf scale=160:190 -b:v 250k -dash 1 video_160x90_250k.webm -an -vf scale=320:180 -b:v 500k -dash 1 video_320x180_500k.webm -an -vf scale=640:360 -b:v 750k -dash 1 video_640x360_750k.webm -an -vf scale=640:360 -b:v 1000k -dash 1 video_640x360_1000k.webm -an -vf scale=1280:720 -b:v 1500k -dash 1 video_1280x720_1500k.webm

  I’m converting a single video into multiple videos at different resolutions. But it’s painfully slow. how can I speed this up ?

• intreadwrite : Indicate potential aliasing in AV_RN/AV_WN for Clang/MSVC mode

  1er août 2023, par Martin Storsjö

  intreadwrite : Indicate potential aliasing in AV_RN/AV_WN for Clang/MSVC mode
  Use the GCC specific codepath for Clang in MSVC mode too.
  
  This matches the condition used in a number of other places.
  MSVC doesn't have a way to signal potential aliasing, while GCC
  
  (and Clang) can use __attribute__((may_alias)) for this purpose.
  When building with Clang in MSVC mode, __GNUC__ isn't defined but
  
  _MSC_VER is as Clang primarily impersonates MSVC - but even then it
  
  does support the GCC style attributes.
  The GCC specific codepath uses av_alias, which expands to
  
  the may_alias attribute if supported. The MSVC specific codepath
  
  doesn't use av_alias so far (as MSVC doesn't support any
  
  corresponding attribute).
  This fixes a couple HEVC decoder tests when built with Clang 14 or
  
  newer in MSVC mode (with issues observed on all of x86_64, armv7
  
  and aarch64).
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavutil/intreadwrite.h

• configure : speed up check_deps()

  5 août 2018, par Avi Halachmi (:avih)

  configure : speed up check_deps()
  x4 - x25 faster.
  check_deps() recursively enables/disables components, and its loop is
  
  iterated nearly 6000 times. It's particularly slow in bash - currently
  
  consuming more than 50% of configure runtime, and about 20% with other
  
  shells.
  This commit applies few local optimizations, most effective first :
  
   Use $1 $2 ... instead of pushvar/popvar, and same at enable_deep*
  
   Abort early in one notable case - empty deps, to avoid costly no-op.
  
   Smaller changes which do add up :
  
    - Handle $cfg_checking locally instead of via enable[d]/disable
  
    - $cfg_checking : test done before inprogress - x2 faster in 50%+
  
    - one eval instead of several at the empty-deps early abort path.
   The "actual work" part is unmodified - just its surroundings.
  Biggest speedups (relative and absolute) are observed with bash.
  Tested-by : Michael Niedermayer <michael@niedermayer.cc>
  
  Tested-by : Helmut K. C. Tessarek <tessarek@evermeet.cx>
  
  Tested-by : Dave Yeo <daveryeo@telus.net>
  
  Tested-by : Reino Wijnsma <rwijnsma@xs4all.nl>
  
  Signed-off-by : James Almer <jamrial@gmail.com>
  

  • [DH] configure