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/*
* High quality image resampling with polyphase filters
* Copyright (c) 2001 Fabrice Bellard
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/**
* @file imgresample_altivec.c
* High quality image resampling with polyphase filters - AltiVec bits
*/
#include "util_altivec.h"
#define FILTER_BITS 8
typedef union {
vector signed short v;
signed short s[8];
} vec_ss;
void v_resample16_altivec(uint8_t *dst, int dst_width, const uint8_t *src,
int wrap, int16_t *filter)
{
int sum, i;
const uint8_t *s;
vector unsigned char *tv, tmp, dstv, zero;
vec_ss srchv[4], srclv[4], fv[4];
vector signed short zeros, sumhv, sumlv;
s = src;
for(i=0;i<4;i++) {
/*
The vec_madds later on does an implicit >>15 on the result.
Since FILTER_BITS is 8, and we have 15 bits of magnitude in
a signed short, we have just enough bits to pre-shift our
filter constants <<7 to compensate for vec_madds.
*/
fv[i].s[0] = filter[i] << (15-FILTER_BITS);
fv[i].v = vec_splat(fv[i].v, 0);
}
zero = vec_splat_u8(0);
zeros = vec_splat_s16(0);
/*
When we're resampling, we'd ideally like both our input buffers,
and output buffers to be 16-byte aligned, so we can do both aligned
reads and writes. Sadly we can't always have this at the moment, so
we opt for aligned writes, as unaligned writes have a huge overhead.
To do this, do enough scalar resamples to get dst 16-byte aligned.
*/
i = (-(int)dst) & 0xf;
while(i>0) {
sum = s[0 * wrap] * filter[0] +
s[1 * wrap] * filter[1] +
s[2 * wrap] * filter[2] +
s[3 * wrap] * filter[3];
sum = sum >> FILTER_BITS;
if (sum<0) sum = 0; else if (sum>255) sum=255;
dst[0] = sum;
dst++;
s++;
dst_width--;
i--;
}
/* Do our altivec resampling on 16 pixels at once. */
while(dst_width>=16) {
/* Read 16 (potentially unaligned) bytes from each of
4 lines into 4 vectors, and split them into shorts.
Interleave the multipy/accumulate for the resample
filter with the loads to hide the 3 cycle latency
the vec_madds have. */
tv = (vector unsigned char *) &s[0 * wrap];
tmp = vec_perm(tv[0], tv[1], vec_lvsl(0, &s[i * wrap]));
srchv[0].v = (vector signed short) vec_mergeh(zero, tmp);
srclv[0].v = (vector signed short) vec_mergel(zero, tmp);
sumhv = vec_madds(srchv[0].v, fv[0].v, zeros);
sumlv = vec_madds(srclv[0].v, fv[0].v, zeros);
tv = (vector unsigned char *) &s[1 * wrap];
tmp = vec_perm(tv[0], tv[1], vec_lvsl(0, &s[1 * wrap]));
srchv[1].v = (vector signed short) vec_mergeh(zero, tmp);
srclv[1].v = (vector signed short) vec_mergel(zero, tmp);
sumhv = vec_madds(srchv[1].v, fv[1].v, sumhv);
sumlv = vec_madds(srclv[1].v, fv[1].v, sumlv);
tv = (vector unsigned char *) &s[2 * wrap];
tmp = vec_perm(tv[0], tv[1], vec_lvsl(0, &s[2 * wrap]));
srchv[2].v = (vector signed short) vec_mergeh(zero, tmp);
srclv[2].v = (vector signed short) vec_mergel(zero, tmp);
sumhv = vec_madds(srchv[2].v, fv[2].v, sumhv);
sumlv = vec_madds(srclv[2].v, fv[2].v, sumlv);
tv = (vector unsigned char *) &s[3 * wrap];
tmp = vec_perm(tv[0], tv[1], vec_lvsl(0, &s[3 * wrap]));
srchv[3].v = (vector signed short) vec_mergeh(zero, tmp);
srclv[3].v = (vector signed short) vec_mergel(zero, tmp);
sumhv = vec_madds(srchv[3].v, fv[3].v, sumhv);
sumlv = vec_madds(srclv[3].v, fv[3].v, sumlv);
/* Pack the results into our destination vector,
and do an aligned write of that back to memory. */
dstv = vec_packsu(sumhv, sumlv) ;
vec_st(dstv, 0, (vector unsigned char *) dst);
dst+=16;
s+=16;
dst_width-=16;
}
/* If there are any leftover pixels, resample them
with the slow scalar method. */
while(dst_width>0) {
sum = s[0 * wrap] * filter[0] +
s[1 * wrap] * filter[1] +
s[2 * wrap] * filter[2] +
s[3 * wrap] * filter[3];
sum = sum >> FILTER_BITS;
if (sum<0) sum = 0; else if (sum>255) sum=255;
dst[0] = sum;
dst++;
s++;
dst_width--;
}
}
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