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ffmpeg/libavcodec/dirac_vlc.c

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/*
* Copyright (C) 2016 Open Broadcast Systems Ltd.
* Author 2016 Rostislav Pehlivanov <rpehlivanov@obe.tv>
*
* 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 "dirac_vlc.h"
#define LUT_SIZE (1 << LUT_BITS)
#define RSIZE_BITS (CHAR_BIT*sizeof(residual))
#define CONVERT_TO_RESIDUE(a, b) \
(((residual)(a)) << (RSIZE_BITS - (b)))
#define INIT_RESIDUE(N) \
residual N = 0; \
av_unused int32_t N ## _bits = 0
#define SET_RESIDUE(N, I, B) \
N = CONVERT_TO_RESIDUE(I, B); \
N ## _bits = B
#define APPEND_RESIDUE(N, M) \
N |= M >> (N ## _bits); \
N ## _bits += (M ## _bits)
int ff_dirac_golomb_read_32bit(DiracGolombLUT *lut_ctx, const uint8_t *buf,
int bytes, uint8_t *_dst, int coeffs)
{
int i, b, c_idx = 0;
int32_t *dst = (int32_t *)_dst;
DiracGolombLUT *future[4], *l = &lut_ctx[2*LUT_SIZE + buf[0]];
INIT_RESIDUE(res);
for (b = 1; b <= bytes; b++) {
future[0] = &lut_ctx[buf[b]];
future[1] = future[0] + 1*LUT_SIZE;
future[2] = future[0] + 2*LUT_SIZE;
future[3] = future[0] + 3*LUT_SIZE;
if ((c_idx + 1) > coeffs)
return c_idx;
/* res_bits is a hint for better branch prediction */
if (res_bits && l->sign) {
int32_t coeff = 1;
APPEND_RESIDUE(res, l->preamble);
for (i = 0; i < (res_bits >> 1) - 1; i++) {
coeff <<= 1;
coeff |= (res >> (RSIZE_BITS - 2*i - 2)) & 1;
}
dst[c_idx++] = l->sign * (coeff - 1);
res_bits = res = 0;
}
memcpy(&dst[c_idx], l->ready, LUT_BITS*sizeof(int32_t));
c_idx += l->ready_num;
APPEND_RESIDUE(res, l->leftover);
l = future[l->need_s ? 3 : !res_bits ? 2 : res_bits & 1];
}
return c_idx;
}
int ff_dirac_golomb_read_16bit(DiracGolombLUT *lut_ctx, const uint8_t *buf,
int bytes, uint8_t *_dst, int coeffs)
{
int i, b, c_idx = 0;
int16_t *dst = (int16_t *)_dst;
DiracGolombLUT *future[4], *l = &lut_ctx[2*LUT_SIZE + buf[0]];
INIT_RESIDUE(res);
for (b = 1; b <= bytes; b++) {
future[0] = &lut_ctx[buf[b]];
future[1] = future[0] + 1*LUT_SIZE;
future[2] = future[0] + 2*LUT_SIZE;
future[3] = future[0] + 3*LUT_SIZE;
if ((c_idx + 1) > coeffs)
return c_idx;
if (res_bits && l->sign) {
int32_t coeff = 1;
APPEND_RESIDUE(res, l->preamble);
for (i = 0; i < (res_bits >> 1) - 1; i++) {
coeff <<= 1;
coeff |= (res >> (RSIZE_BITS - 2*i - 2)) & 1;
}
dst[c_idx++] = l->sign * (coeff - 1);
res_bits = res = 0;
}
for (i = 0; i < LUT_BITS; i++)
dst[c_idx + i] = l->ready[i];
c_idx += l->ready_num;
APPEND_RESIDUE(res, l->leftover);
l = future[l->need_s ? 3 : !res_bits ? 2 : res_bits & 1];
}
return c_idx;
}
/* Searches for golomb codes in a residue */
static inline void search_for_golomb(DiracGolombLUT *l, residual r, int bits)
{
int r_count = RSIZE_BITS - 1;
int bits_start, bits_tot = bits, need_sign = 0;
#define READ_BIT(N) (((N) >> (N ## _count--)) & 1)
while (1) {
int32_t coef = 1;
bits_start = (RSIZE_BITS - 1) - r_count;
while (1) {
if (!bits--)
goto leftover;
if (READ_BIT(r))
break;
coef <<= 1;
if (!bits--)
goto leftover;
coef |= READ_BIT(r);
}
l->ready[l->ready_num] = coef - 1;
if (l->ready[l->ready_num]) {
if (!bits--) {
need_sign = 1;
goto leftover;
}
l->ready[l->ready_num] *= READ_BIT(r) ? -1 : +1;
}
l->ready_num++;
if (!bits)
return;
}
leftover:
l->leftover = r << bits_start;
l->leftover_bits = bits_tot - bits_start;
l->need_s = need_sign;
}
/* Parity LUTs - even and odd bit end positions */
static void generate_parity_lut(DiracGolombLUT *lut, int even)
{
int idx;
for (idx = 0; idx < LUT_SIZE; idx++) {
DiracGolombLUT *l = &lut[idx];
int symbol_end_loc = -1;
uint32_t code;
int i;
INIT_RESIDUE(res);
SET_RESIDUE(res, idx, LUT_BITS);
for (i = 0; i < LUT_BITS; i++) {
const int cond = even ? (i & 1) : !(i & 1);
if (((res >> (RSIZE_BITS - i - 1)) & 1) && cond) {
symbol_end_loc = i + 2;
break;
}
}
if (symbol_end_loc < 0 || symbol_end_loc > LUT_BITS) {
l->preamble = 0;
l->preamble_bits = 0;
l->leftover_bits = LUT_BITS;
l->leftover = CONVERT_TO_RESIDUE(idx, l->leftover_bits);
if (even)
l->need_s = idx & 1;
continue;
}
/* Gets bits 0 through to (symbol_end_loc - 1) inclusive */
code = idx >> ((LUT_BITS - 1) - (symbol_end_loc - 1));
code &= ((1 << LUT_BITS) - 1) >> (LUT_BITS - symbol_end_loc);
l->preamble_bits = symbol_end_loc;
l->preamble = CONVERT_TO_RESIDUE(code, l->preamble_bits);
l->sign = ((l->preamble >> (RSIZE_BITS - l->preamble_bits)) & 1) ? -1 : +1;
search_for_golomb(l, res << symbol_end_loc, LUT_BITS - symbol_end_loc);
}
}
/* Reset (off == 0) and needs-one-more-bit (off == 1) LUTs */
static void generate_offset_lut(DiracGolombLUT *lut, int off)
{
int idx;
for (idx = 0; idx < LUT_SIZE; idx++) {
DiracGolombLUT *l = &lut[idx];
INIT_RESIDUE(res);
SET_RESIDUE(res, idx, LUT_BITS);
l->preamble = CONVERT_TO_RESIDUE(res >> (RSIZE_BITS - off), off);
l->preamble_bits = off;
l->sign = ((l->preamble >> (RSIZE_BITS - l->preamble_bits)) & 1) ? -1 : +1;
search_for_golomb(l, res << off, LUT_BITS - off);
}
}
av_cold int ff_dirac_golomb_reader_init(DiracGolombLUT **lut_ctx)
{
DiracGolombLUT *lut;
if (!(lut = av_calloc(4*LUT_SIZE, sizeof(DiracGolombLUT))))
return AVERROR(ENOMEM);
generate_parity_lut(&lut[0*LUT_SIZE], 0);
generate_parity_lut(&lut[1*LUT_SIZE], 1);
generate_offset_lut(&lut[2*LUT_SIZE], 0);
generate_offset_lut(&lut[3*LUT_SIZE], 1);
*lut_ctx = lut;
return 0;
}
av_cold void ff_dirac_golomb_reader_end(DiracGolombLUT **lut_ctx)
{
av_freep(lut_ctx);
}
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