mirror of
https://github.com/mpv-player/mpv
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2eb3f24dc1
git-svn-id: svn://svn.mplayerhq.hu/mplayer/trunk@4790 b3059339-0415-0410-9bf9-f77b7e298cf2
73 lines
2.2 KiB
C
73 lines
2.2 KiB
C
/*=============================================================================
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//
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// This software has been released under the terms of the GNU Public
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// license. See http://www.gnu.org/copyleft/gpl.html for details.
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//
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// Copyright 2001 Anders Johansson ajh@atri.curtin.edu.au
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//
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//=============================================================================
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*/
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#ifndef __FIR_H__
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#define __FIR_H__
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/* Fixpoint 16 bit FIR filter. The filter is implemented both in C and
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MMX assembly. The filter consists of the two inline functions updateq
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and firn, update q is used for adding new data to the circular buffer
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used by the filter firn. Limitations: max length of n = 16*4 and n
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must be multiple of 4 (pad fiter with zeros for other lengths).
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Sometimes it works with filters longer than 4*16 (the problem is
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overshoot and the acumulated energy in the filter taps). */
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#ifdef HAVE_MMX
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inline int32_t firn(int16_t* x, int16_t* w, int16_t n)
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{
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register int32_t y; // Output
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// Prologue
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asm volatile(" pxor %mm1, %mm1;\n" ); // Clear buffer yt
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// Main loop
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while((n-=4)>=0){
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asm volatile(
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" movq (%1), %%mm0;\n" // Load x(n:n+4)
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" pmaddwd (%0), %%mm0;\n" // yt(n:n+1)=sum(x(n:n+4).*w(n:n+4))
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" psrld $16, %%mm0;\n" // yt(n:n+1)=yt(n:n+1)>>16
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" paddd %%mm0, %%mm1;\n" // yt(n:n+1)=yt(n-2:n-1)+yt(n:n+1)
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:: "r" (w), "r" (x));
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w+=4; x+=4;
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}
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// Epilogue
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asm volatile(
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" movq %%mm1, %%mm0;\n"
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" punpckhdq %%mm1, %%mm0;\n"
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" paddd %%mm0, %%mm1;\n" //yt(n)=yt(n)+yt(n+1)
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" movd %%mm1, %0 ;\n" //y=yt
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" emms ;\n"
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: "=&r" (y));
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return y;
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}
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#else /* HAVE_MMX */
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// Same thing as above but in C
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inline int32_t firn(int16_t* x, int16_t* w, int16_t n)
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{
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register int32_t y=0;
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while((n-=4) >=0)
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y+=w[n]*x[n]+w[n+1]*x[n+1]+w[n+2]*x[n+2]+w[n+3]*x[n+3] >> 16;
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return y;
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}
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#endif /* HAVE_MMX */
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/* Add new data to circular queue designed to be used with a FIR
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filter. xq is the circular queue, in pointing at the new sample, xi
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current index for in xq and l the lenght of the filter */
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inline uint16_t updateq(int16_t* xq, int16_t* in, uint16_t xi, uint16_t l)
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{
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xq[xi]=xq[xi+l]=*in;
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return (--xi)&(l-1); \
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}
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#endif /* __FIR_H__ */
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