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• aarch64 : Use regular hwcaps flags instead of HWCAP_CPUID for CPU feature detection...

  14 février 2024, par Martin Storsjö

  aarch64 : Use regular hwcaps flags instead of HWCAP_CPUID for CPU feature detection on Linux
  This makes the code much simpler (especially for adding support
  
  for other instruction set extensions), avoids needing inline
  
  assembly for this feature, and generally is more of the canonical
  
  way to do this.
  The CPU feature detection was added in
  
  493fcde50a84cb23854335bcb0e55c6f383d55db, using HWCAP_CPUID.
  The argument for using that, was that HWCAP_CPUID was added much
  
  earlier in the kernel (in Linux v4.11), while the HWCAP flags for
  
  individual features always come later. This allows detecting support
  
  for new CPU extensions before the kernel exposes information about
  
  them via hwcap flags.
  However in practice, there's probably quite little advantage in this.
  
  E.g. HWCAP2_I8MM was added in Linux v5.10 - long after HWCAP_CPUID,
  
  but there's probably very little practical cases where one would
  
  run a kernel older than that on a CPU that supports those instructions.
  Additionally, we provide our own definitions of the flag values to
  
  check (as they are fixed constants anyway), with names not conflicting
  
  with the ones from system headers. This reduces the number of ifdefs
  
  needed, and allows detecting those features even if building with
  
  userland headers that are lacking the definitions of those flags.
  Also, slightly older versions of QEMU, e.g. 6.2 in Ubuntu 22.04,
  
  do expose support for these features via HWCAP flags, but the
  
  emulated cpuid registers are missing the bits for exposing e.g. I8MM.
  
  (This issue is fixed in later versions of QEMU though.)
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] libavutil/aarch64/cpu.c

• avcodec : add common fflcms2 boilerplate

  28 juin 2022, par Niklas Haas

  avcodec : add common fflcms2 boilerplate
  Handling this in general code makes more sense than handling it in
  
  individual codec files, because it would be a lot of unnecessary code
  
  duplication for the plenty of formats that support exporting ICC
  
  profiles (jpg, png, tiff, webp, jxl, ...).
  encode.c and decode.c will be in charge of initializing this state as
  
  needed, so we merely need to make sure to uninit it afterwards from the
  
  common destructor path.
  Signed-off-by : Niklas Haas <git@haasn.dev>
  

  • [DH] configure
  • [DH] libavcodec/Makefile
  • [DH] libavcodec/avcodec.c
  • [DH] libavcodec/decode.c
  • [DH] libavcodec/internal.h

• Can't split 24bit flac files on the command line [closed]

  21 mars 2023, par Martin

  I am trying to export a 24bit flac file in my ubuntu terminal. I've tried two different methods, but neither work.

  


  Method 1 : shntool

  


  when I run this command :
shntool split -f times.cue -O always -o lowq_full_silence.flac

  


  where lowq_full_silence.flac was rendered in audacity as a flac file with level=0 and bit depth=16 bit, my command works.

  


  but if i run this command :

  


  shntool split -f times.cue -O always -o full_hq.flac

  


  where full_hq.flac has level=8 and bit depth=24 bit
The command fails :

  


  shntool [split]: warning: unsupported format 0xfffe (Unknown) while processing file: [full_hq.flac]
shntool [split]: error: cannot continue due to error(s) shown above


  


  https://bugs.launchpad.net/ubuntu/+source/shntool/+bug/2000794

  


  Method 2 : ffmpeg

  


  Trying to split the flac file with comma separated 'split points' input

  


  ffmpeg -i "full_hq.flac" -c copy -map 0 -f segment -segment_times "22,441,556,559" "%d_output.flac"

  


  But the output from this ffmpeg command has broken length metadata :

  


  https://trac.ffmpeg.org/ticket/4905

  


  Is there a better way to split a high quality 24bit flac file into individual segments, where each exported segment file has correct length metadata ?

  


  Files :
https://file.io/lvGTUEgQArb7