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• lavc/aacpsdsp : RISC-V V hybrid_analysis

  26 septembre 2022, par Rémi Denis-Courmont

  lavc/aacpsdsp : RISC-V V hybrid_analysis
  This starts with one-time initialisation of the 26 constant factors
  
  like  08edacc248bce3f8946d75e97188d189c74a6de6. That is done with
  
  the scalar instruction set. While the formula can readily be vectored,
  
  the gains would (probably) be more than lost in transfering the results
  
  back to FP registers (or suitably reshuffling them into vector
  
  registers).
  Note that the main loop could likely be scheduled sligthly better by
  
  expanding the filter macro and interleaving loads with arithmetic.
  
  It is not clear yet if that would be relevant for vector processing (as
  
  opposed to traditional SIMD).
  We could also use fewer vectors, but there is not much point in sparing
  
  them (they are *all* callee-clobbered).
  

  • [DH] libavcodec/riscv/aacpsdsp_init.c
  • [DH] libavcodec/riscv/aacpsdsp_rvv.S

• Disadvantages to creating/removing many hard links ?

  6 novembre 2011, par agartland

  I need to create hundreds to thousands of temporary hard or symbolic links that will be deleted shortly after creation. For my purposes both types of links will work (i.e. the target is not a directory and it always exists on the same file system)

  As I understand it, symbolic links create a small file that contains the path to the original file. Whereas a hardlink creates a reference to the data in the same inode. So maybe if I am going to be creating/deleting thousands of these links is it better to be creating and deleting thousands of tiny files (symlinks) or thousands of these references (hardlinks) ? It seems like one taxes the hard drive (maybe fragmentation) while the other might tax the file system itself ? Where are inode references stored. Do I risk corrupting the file system by making so many hard links ? What about speed ?

  Thanks for your expertise !

  This a work around to be able to use ffmpeg to encode a movie out of an arbitrary subset of images from a directory. Since ffmpeg requires that the files be named properly (e.g. frame%04d.jpg) I realized I can just create hard/sym links to the subset of files and just name the links appropriately. This avoids renaming the original files and having to actually copy the data. It works great but it requires creating and deleting many thousands of links, repeatedly.

  Sort of addresses this problem too I believe :
  convert image sequence using ffmpeg

• fate : Use a oneoff test for the tremolo filter

  9 décembre 2019, par Martin Storsjö

  fate : Use a oneoff test for the tremolo filter
  The tremolo filter uses floating point internally, and uses
  
  multiplication factors derived from sin(fmod()), neither of
  
  which is bitexact for use with framecrc.
  This fixes running this test when built with for mingw/x86_32
  
  with clang.
  In this case, a 1 ulp difference in the output from fmod() would
  
  end up in an output from the filter that differs by 1 ulp, but
  
  which makes the lrint() in swresample/audioconvert.c round in a
  
  different direction.
  Signed-off-by : Martin Storsjö <martin@martin.st>
  

  • [DH] tests/fate/filter-audio.mak
  • [DH] tests/ref/fate/filter-tremolo