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• 3 million downloads for Piwik Analytics

  11 janvier 2017, par Matthieu Aubry — Community

  A testament to the power of our mission statement…

  “To create, as a community, the leading international open source digital analytics platform, that gives every user full control of their data.”

  … Piwik has been downloaded more than 3 million times !

  

  Piwik is the most popular open analytics platform

  Piwik is the number one most popular open analytics platform, used on more than 1 million websites in 200 different countries, and the 7th overall most popular analytics tool.

  Together we can make Piwik even better !

  Piwik is a community project. We are so proud of what we have created and would love your help too ! Help us by filling in our community survey (takes just 5 minutes !), by getting involved or becoming a sponsor.

  Thank you so much for using Piwik and respecting privacy while keeping control of your data.

  Happy Analytics !

• imdct15 : remove the AArch64 assembly

  4 janvier 2017, par Rostislav Pehlivanov

  imdct15 : remove the AArch64 assembly
  Prep work for the next commit, which will add a new FFT algorithm
  
  which makes the iMDCT over 3x faster than it is currently (standalone,
  
  the FFT is with some framesizes over 10x faster).
  The new FFT algorithm uses the already thouroughly SIMD’d power of two
  
  FFT which already has SIMD for AArch64, so users of that platform will
  
  still see an improvement.
  The previous FFT+SIMD was barely 2.5x faster than the C versions on these
  
  platforms.
  Signed-off-by : Rostislav Pehlivanov <atomnuker@gmail.com>
  

  • [DH] libavcodec/aarch64/Makefile
  • [DH] libavcodec/aarch64/imdct15_init.c
  • [DH] libavcodec/aarch64/imdct15_neon.S
  • [DH] libavcodec/imdct15.c
  • [DH] libavcodec/imdct15.h

• imdct15 : replace the FFT with a faster PFA FFT algorithm

  4 janvier 2017, par Rostislav Pehlivanov

  imdct15 : replace the FFT with a faster PFA FFT algorithm
  This commit replaces the current inefficient non-power-of-two FFT with a
  
  much faster FFT based on the Prime Factor Algorithm.
  
  Although it is already much faster than the old algorithm without SIMD,
  
  the new algorithm makes use of the already very throughouly SIMD’d power
  
  of two FFT, which improves performance even more across all platforms
  
  which we have SIMD support for.
  Most of the work was done by Peter Barfuss, who passed the code to me to
  
  implement into the iMDCT and the current codebase. The code for a
  
  5-point and 15-point FFT was derived from the previous implementation,
  
  although it was optimized and simplified, which will make its future
  
  SIMD easier. The 15-point FFT is currently using 6% of the current
  
  overall decoder overhead.
  The FFT can now easily be used as a forward transform by simply not
  
  multiplying the 5-point FFT’s imaginary component by -1 (which comes
  
  from the fact that changing the complex exponential’s angle by -1 also
  
  changes the output by that) and by multiplying the "theta" angle of the
  
  main exptab by -1. Hence the deliberately left multiplication by -1 at
  
  the end.
  FATE passes, and performance reports on other platforms/CPUs are
  
  welcome.
  Performance comparisons :
  iMDCT, PFA :
  
  101127 decicycles in speed,   32765 runs,      3 skips
  
  iMDCT, Old :
  
  211022 decicycles in speed,   32768 runs,      0 skips
  Standalone FFT, 300000 transforms of size 960 :
  
      PFA        Old FFT     kiss_fft    libfftw3f
  
      3.659695s, 15.726912s, 13.300789s, 1.182222s
  Being only 3x slower than libfftw3f is a big achievement by itself.
  There appears to be something capping the performance in the iMDCT side
  
  of things, possibly during the pre-stage reindexing. However, it is
  
  certainly fast enough for now.
  Signed-off-by : Rostislav Pehlivanov <atomnuker@gmail.com>
  

  • [DH] libavcodec/imdct15.c
  • [DH] libavcodec/imdct15.h