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• Does Apple AS assembler replace certain NEON instructions with equivalent ones on iOS ?

  5 avril 2012, par Yi Wang

  I was trying to use ffmpeg on iOS and was debugging a crash in the optimized arm code. I have discovered that some unsigned (.u16, .u32) instruction have been replaced by signed ones (.i16, .i32). It's easy to see because disassembled instruction on GDB doesn't quite match the source code.

  For example,

  vrshrn.u32 -> vrshrn.i32
  
  vrshrn.u16 -> vrshrn.i16
  
  vadd.u16 -> vadd.i16

  My questions :

  1. Is this behavior correct and expected ? If not, how do we correct it ?
  2. If they are equivalent, why do we nee need the unsigned ones at all ? Is it because that way the code is more explicit ?
  3. Is this behavior expected with other platform's toolkit ? For example, Android's toolkit ? (I have heard Apple's AS is an ancient one)

• error while compiling x264 in linux

  14 avril 2011, par kartul

  Hey all
  I'm trying to compile x264 under linux (x64). But it keeps throwing me an error. I've googled around but found nothing. Here's the commandline history :

  spin@around : /x264$ git clone git ://git.videolan.org/x264.git
  Cloning into x264...
  remote : Counting objects : 13539, done.
  remote : Compressing objects : 100% (4416/4416), done.
  remote : Total 13539 (delta 11005), reused 11225 (delta 9082)
  Receiving objects : 100% (13539/13539), 3.29 MiB | 2.79 MiB/s, done.
  Resolving deltas : 100% (11005/11005), done.
  spin@around : /x264/x264$ ./configure
  Found no assembler
  Minimum version is yasm-0.7.0
  If you really want to compile without asm, configure with —disable-asm.
  spin@around : /x264/x264$ ./configure —disable-asm
  Platform :   X86_64
  System :     LINUX
  asm :        no
  avs :        no
  lavf :       no
  ffms :       no
  gpac :       no
  gpl :        yes
  thread :     posix
  filters :    crop select_every
  debug :      no
  gprof :      no
  PIC :        no
  shared :     no
  visualize :  no
  bit depth :  8
  You can run 'make' or 'make fprofiled' now.
  
  spin@around : /x264/x264$ make
  
  gcc -Wshadow -O3 -ffast-math  -Wall -I. -std=gnu99 -s -fomit-frame-pointer -fno-tree-vectorize   -c -o x264.o x264.c
  
  In file included from common/common.h:864,
  
                   from x264.c:33 :
  
  common/rectangle.h : In function āx264_macroblock_cache_rectā :
  
  common/rectangle.h:84 : error : āv4siā undeclared (first use in this function)
  
  common/rectangle.h:84 : error : (Each undeclared identifier is reported only once
  
  common/rectangle.h:84 : error : for each function it appears in.)
  
  common/rectangle.h:84 : error : expected ā ;ā before āv16ā
  
  common/rectangle.h:86 : error : ā__m128ā undeclared (first use in this function)
  
  common/rectangle.h:86 : error : expected ā ;ā before āv16ā
  
  common/rectangle.h:87 : error : expected ā ;ā before āv16ā
  
  common/rectangle.h:89 : error : expected ā ;ā before āv16ā
  
  common/rectangle.h:90 : error : expected ā ;ā before āv16ā
  
  make : *** [x264.o] Error 1
  
  spin@around : /x264/x264$
  

  and here is the file, from line 83 to 91 :

  #if HAVE_VECTOREXT && defined(__SSE__)
          v4si v16 = v,v,v,v ;
          M128( d+s*0+0 ) = (__m128)v16 ;
  
          M128( d+s*1+0 ) = (__m128)v16 ;
  
          if( h == 2 ) return ;
  
          M128( d+s*2+0 ) = (__m128)v16 ;
  
          M128( d+s*3+0 ) = (__m128)v16 ;
  
  #else
  

• GSoC : Support fast guided filter.

  10 mai 2021, par Xuewei Meng

  GSoC : Support fast guided filter.
  Two modes are supported in guided filter, basic mode and fast mode.
  
  Basic mode is the initial pushed guided filter without optimization.
  
  Fast mode is implemented based on the basic one by sub-sampling method.
  
  The sub-sampling ratio which can be defined by users controls the
  
  algorithm complexity. The larger the sub-sampling ratio, the lower
  
  the algorithm complexity.
  Signed-off-by : Xuewei Meng <xwmeng96@gmail.com>
  
  Reviewed-by : Steven Liu <liuqi05@kuaishou.com>
  

  • [DH] doc/filters.texi
  • [DH] libavfilter/vf_guided.c