mirror of
https://gitee.com/openharmony/third_party_ffmpeg
synced 2024-11-24 03:39:45 +00:00
91126dc481
I found the optimisation of 2 samples per iteration obscured the underlying algorithm. I had to write it out on paper and translate into a mathematical sum to see that the two samples are unconnected. I hope that if anyone else is struggling to understand the code that this will be useful. Reviewed-by: Christophe Gisquet <christophe.gisquet@gmail.com> Signed-off-by: Michael Niedermayer <michaelni@gmx.at>
160 lines
5.0 KiB
C
160 lines
5.0 KiB
C
/*
|
|
* 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
|
|
*/
|
|
|
|
#include <stdint.h>
|
|
#include "libavutil/avutil.h"
|
|
#include "mathops.h"
|
|
|
|
#undef FUNC
|
|
#undef sum_type
|
|
#undef MUL
|
|
#undef CLIP
|
|
#undef FSUF
|
|
|
|
#define FUNC(n) AV_JOIN(n ## _, SAMPLE_SIZE)
|
|
|
|
#if SAMPLE_SIZE == 32
|
|
# define sum_type int64_t
|
|
# define MUL(a, b) MUL64(a, b)
|
|
# define CLIP(x) av_clipl_int32(x)
|
|
#else
|
|
# define sum_type int32_t
|
|
# define MUL(a, b) ((a) * (b))
|
|
# define CLIP(x) (x)
|
|
#endif
|
|
|
|
#define LPC1(x) { \
|
|
int c = coefs[(x)-1]; \
|
|
p0 += MUL(c, s); \
|
|
s = smp[i-(x)+1]; \
|
|
p1 += MUL(c, s); \
|
|
}
|
|
|
|
static av_always_inline void FUNC(lpc_encode_unrolled)(int32_t *res,
|
|
const int32_t *smp, int len, int order,
|
|
const int32_t *coefs, int shift, int big)
|
|
{
|
|
int i;
|
|
for (i = order; i < len; i += 2) {
|
|
int s = smp[i-order];
|
|
sum_type p0 = 0, p1 = 0;
|
|
if (big) {
|
|
switch (order) {
|
|
case 32: LPC1(32)
|
|
case 31: LPC1(31)
|
|
case 30: LPC1(30)
|
|
case 29: LPC1(29)
|
|
case 28: LPC1(28)
|
|
case 27: LPC1(27)
|
|
case 26: LPC1(26)
|
|
case 25: LPC1(25)
|
|
case 24: LPC1(24)
|
|
case 23: LPC1(23)
|
|
case 22: LPC1(22)
|
|
case 21: LPC1(21)
|
|
case 20: LPC1(20)
|
|
case 19: LPC1(19)
|
|
case 18: LPC1(18)
|
|
case 17: LPC1(17)
|
|
case 16: LPC1(16)
|
|
case 15: LPC1(15)
|
|
case 14: LPC1(14)
|
|
case 13: LPC1(13)
|
|
case 12: LPC1(12)
|
|
case 11: LPC1(11)
|
|
case 10: LPC1(10)
|
|
case 9: LPC1( 9)
|
|
LPC1( 8)
|
|
LPC1( 7)
|
|
LPC1( 6)
|
|
LPC1( 5)
|
|
LPC1( 4)
|
|
LPC1( 3)
|
|
LPC1( 2)
|
|
LPC1( 1)
|
|
}
|
|
} else {
|
|
switch (order) {
|
|
case 8: LPC1( 8)
|
|
case 7: LPC1( 7)
|
|
case 6: LPC1( 6)
|
|
case 5: LPC1( 5)
|
|
case 4: LPC1( 4)
|
|
case 3: LPC1( 3)
|
|
case 2: LPC1( 2)
|
|
case 1: LPC1( 1)
|
|
}
|
|
}
|
|
res[i ] = smp[i ] - CLIP(p0 >> shift);
|
|
res[i+1] = smp[i+1] - CLIP(p1 >> shift);
|
|
}
|
|
}
|
|
|
|
static void FUNC(flac_lpc_encode_c)(int32_t *res, const int32_t *smp, int len,
|
|
int order, const int32_t *coefs, int shift)
|
|
{
|
|
int i;
|
|
for (i = 0; i < order; i++)
|
|
res[i] = smp[i];
|
|
#if CONFIG_SMALL
|
|
for (i = order; i < len; i += 2) {
|
|
int j;
|
|
int s = smp[i];
|
|
sum_type p0 = 0, p1 = 0;
|
|
for (j = 0; j < order; j++) {
|
|
int c = coefs[j];
|
|
p1 += MUL(c, s);
|
|
s = smp[i-j-1];
|
|
p0 += MUL(c, s);
|
|
}
|
|
res[i ] = smp[i ] - CLIP(p0 >> shift);
|
|
res[i+1] = smp[i+1] - CLIP(p1 >> shift);
|
|
}
|
|
#else
|
|
switch (order) {
|
|
case 1: FUNC(lpc_encode_unrolled)(res, smp, len, 1, coefs, shift, 0); break;
|
|
case 2: FUNC(lpc_encode_unrolled)(res, smp, len, 2, coefs, shift, 0); break;
|
|
case 3: FUNC(lpc_encode_unrolled)(res, smp, len, 3, coefs, shift, 0); break;
|
|
case 4: FUNC(lpc_encode_unrolled)(res, smp, len, 4, coefs, shift, 0); break;
|
|
case 5: FUNC(lpc_encode_unrolled)(res, smp, len, 5, coefs, shift, 0); break;
|
|
case 6: FUNC(lpc_encode_unrolled)(res, smp, len, 6, coefs, shift, 0); break;
|
|
case 7: FUNC(lpc_encode_unrolled)(res, smp, len, 7, coefs, shift, 0); break;
|
|
case 8: FUNC(lpc_encode_unrolled)(res, smp, len, 8, coefs, shift, 0); break;
|
|
default: FUNC(lpc_encode_unrolled)(res, smp, len, order, coefs, shift, 1); break;
|
|
}
|
|
#endif
|
|
}
|
|
|
|
/* Comment for clarity/de-obfuscation.
|
|
*
|
|
* for (int i = order; i < len; i++) {
|
|
* int32_t p = 0;
|
|
* for (int j = 0; j < order; j++) {
|
|
* int c = coefs[j];
|
|
* int s = smp[(i-1)-j];
|
|
* p += c*s;
|
|
* }
|
|
* res[i] = smp[i] - (p >> shift);
|
|
* }
|
|
*
|
|
* The CONFIG_SMALL code above simplifies to this, in the case of SAMPLE_SIZE
|
|
* not being equal to 32 (at the present time that means for 16-bit audio). The
|
|
* code above does 2 samples per iteration. Commit bfdd5bc ( made all the way
|
|
* back in 2007) says that way is faster.
|
|
*/
|