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FFmpeg/libavcodec/elsdec.c

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/*
* ELS (Entropy Logarithmic-Scale) decoder
*
* Copyright (c) 2013 Maxim Poliakovski
*
* 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
* Entropy Logarithmic-Scale binary arithmetic decoder
*/
#include <math.h>
#include <stdint.h>
#include "libavutil/common.h"
#include "libavutil/intreadwrite.h"
#include "elsdec.h"
/* ELS coder constants and structures. */
#define ELS_JOTS_PER_BYTE 36
#define ELS_MAX (1 << 24)
#define RUNG_SPACE (64 * sizeof(ElsRungNode))
/* ELS coder tables. */
static const struct Ladder {
int8_t AMps;
int8_t ALps;
uint8_t next0;
uint8_t next1;
} Ladder[174] = {
{ -6, -5, 2, 1 },
{ -2, -12, 3, 6 },
{ -2, -12, 4, 6 },
{ -1, -16, 7, 5 },
{ -1, -16, 8, 10 },
{ -5, -6, 11, 9 },
{ -6, -5, 10, 5 },
{ -1, -18, 13, 11 },
{ -1, -18, 12, 14 },
{ -6, -5, 15, 18 },
{ -5, -6, 14, 9 },
{ -3, -8, 17, 15 },
{ -1, -20, 20, 16 },
{ -1, -20, 23, 17 },
{ -3, -8, 16, 18 },
{ -5, -6, 19, 26 },
{ -3, -9, 22, 24 },
{ -3, -9, 21, 19 },
{ -5, -6, 24, 26 },
{ -4, -7, 27, 25 },
{ -1, -22, 34, 28 },
{ -2, -11, 29, 27 },
{ -2, -11, 28, 30 },
{ -1, -22, 39, 29 },
{ -4, -7, 30, 32 },
{ -6, -5, 33, 31 },
{ -6, -5, 32, 25 },
{ -3, -8, 35, 33 },
{ -2, -12, 36, 38 },
{ -2, -12, 37, 35 },
{ -3, -8, 38, 40 },
{ -6, -5, 41, 48 },
{ -6, -5, 40, 31 },
{ -5, -6, 43, 41 },
{ -1, -24, 94, 42 },
{ -3, -8, 45, 43 },
{ -2, -12, 42, 44 },
{ -2, -12, 47, 45 },
{ -3, -8, 44, 46 },
{ -1, -24, 125, 47 },
{ -5, -6, 46, 48 },
{ -6, -5, 49, 49 },
{ -2, -13, 152, 164 },
{ -4, -7, 51, 49 },
{ -3, -9, 164, 168 },
{ -3, -9, 55, 51 },
{ -4, -7, 168, 170 },
{ -2, -13, 67, 55 },
{ -6, -5, 170, 49 },
{ -6, -5, 51, 170 },
{ -1, -72, 50, 74 },
{ -4, -7, 53, 49 },
{ -1, -61, 50, 74 },
{ -3, -8, 55, 49 },
{ -1, -51, 52, 76 },
{ -3, -9, 57, 51 },
{ -1, -46, 54, 76 },
{ -2, -10, 59, 53 },
{ -1, -43, 56, 78 },
{ -2, -11, 61, 53 },
{ -1, -41, 58, 80 },
{ -2, -12, 63, 55 },
{ -1, -39, 60, 82 },
{ -2, -12, 65, 55 },
{ -1, -37, 62, 84 },
{ -2, -13, 67, 57 },
{ -1, -36, 64, 86 },
{ -1, -14, 69, 59 },
{ -1, -35, 66, 88 },
{ -1, -14, 71, 59 },
{ -1, -34, 68, 90 },
{ -1, -15, 73, 61 },
{ -1, -33, 70, 92 },
{ -1, -15, 75, 61 },
{ -1, -32, 72, 94 },
{ -1, -15, 77, 63 },
{ -1, -31, 74, 96 },
{ -1, -16, 79, 65 },
{ -1, -31, 76, 98 },
{ -1, -16, 81, 67 },
{ -1, -30, 78, 100 },
{ -1, -17, 83, 67 },
{ -1, -29, 80, 102 },
{ -1, -17, 85, 69 },
{ -1, -29, 82, 104 },
{ -1, -18, 87, 71 },
{ -1, -28, 84, 104 },
{ -1, -18, 89, 73 },
{ -1, -28, 86, 108 },
{ -1, -18, 91, 73 },
{ -1, -27, 88, 108 },
{ -1, -19, 93, 75 },
{ -1, -27, 90, 112 },
{ -1, -19, 95, 77 },
{ -1, -26, 92, 112 },
{ -1, -20, 97, 79 },
{ -1, -26, 94, 114 },
{ -1, -20, 99, 81 },
{ -1, -25, 96, 116 },
{ -1, -20, 101, 83 },
{ -1, -25, 98, 118 },
{ -1, -21, 103, 83 },
{ -1, -24, 100, 120 },
{ -1, -21, 105, 85 },
{ -1, -24, 102, 122 },
{ -1, -22, 107, 87 },
{ -1, -23, 104, 124 },
{ -1, -22, 109, 89 },
{ -1, -23, 106, 126 },
{ -1, -22, 111, 91 },
{ -1, -22, 108, 128 },
{ -1, -23, 113, 93 },
{ -1, -22, 110, 130 },
{ -1, -23, 115, 95 },
{ -1, -22, 112, 132 },
{ -1, -24, 117, 97 },
{ -1, -21, 114, 134 },
{ -1, -24, 119, 99 },
{ -1, -21, 116, 136 },
{ -1, -25, 121, 101 },
{ -1, -20, 118, 136 },
{ -1, -25, 123, 103 },
{ -1, -20, 120, 138 },
{ -1, -26, 125, 105 },
{ -1, -20, 122, 140 },
{ -1, -26, 127, 107 },
{ -1, -19, 124, 142 },
{ -1, -27, 129, 107 },
{ -1, -19, 126, 144 },
{ -1, -27, 131, 111 },
{ -1, -18, 128, 146 },
{ -1, -28, 133, 111 },
{ -1, -18, 130, 146 },
{ -1, -28, 135, 115 },
{ -1, -18, 132, 148 },
{ -1, -29, 137, 115 },
{ -1, -17, 134, 150 },
{ -1, -29, 139, 117 },
{ -1, -17, 136, 152 },
{ -1, -30, 141, 119 },
{ -1, -16, 138, 152 },
{ -1, -31, 143, 121 },
{ -1, -16, 140, 154 },
{ -1, -31, 145, 123 },
{ -1, -15, 142, 156 },
{ -1, -32, 147, 125 },
{ -1, -15, 144, 158 },
{ -1, -33, 149, 127 },
{ -1, -15, 146, 158 },
{ -1, -34, 151, 129 },
{ -1, -14, 148, 160 },
{ -1, -35, 153, 131 },
{ -1, -14, 150, 160 },
{ -1, -36, 155, 133 },
{ -2, -13, 152, 162 },
{ -1, -37, 157, 135 },
{ -2, -12, 154, 164 },
{ -1, -39, 159, 137 },
{ -2, -12, 156, 164 },
{ -1, -41, 161, 139 },
{ -2, -11, 158, 166 },
{ -1, -43, 163, 141 },
{ -2, -10, 160, 166 },
{ -1, -46, 165, 143 },
{ -3, -9, 162, 168 },
{ -1, -51, 167, 143 },
{ -3, -8, 164, 170 },
{ -1, -61, 169, 145 },
{ -4, -7, 166, 170 },
{ -1, -72, 169, 145 },
{ -6, -5, 168, 49 },
{ 0, -108, 171, 171 },
{ 0, -108, 172, 172 },
{ -6, -5, 173, 173 },
};
static const uint32_t els_exp_tab[ELS_JOTS_PER_BYTE * 4 + 1] = {
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 1, 1, 1, 1,
1, 2, 2, 2, 3, 4, 4, 5,
6, 7, 8, 10, 11, 13, 16, 18,
21, 25, 29, 34, 40, 47, 54, 64,
74, 87, 101, 118, 138, 161, 188, 219,
256, 298, 348, 406, 474, 552, 645, 752,
877, 1024, 1194, 1393, 1625, 1896, 2211, 2580,
3010, 3511, 4096, 4778, 5573, 6501, 7584, 8847,
10321, 12040, 14045, 16384, 19112, 22295, 26007, 30339,
35391, 41285, 48160, 56180, 65536, 76288, 89088, 103936,
121344, 141312, 165120, 192512, 224512, 262144, 305664, 356608,
416000, 485376, 566016, 660480, 770560, 898816, 1048576, 1223168,
1426688, 1664256, 1941504, 2264832, 2642176, 3082240, 3595520, 4194304,
4892672, 5707520, 6657792, 7766784, 9060096, 10568960, 12328960, 14382080,
16777216,
};
void ff_els_decoder_init(ElsDecCtx *ctx, const uint8_t *in, size_t data_size)
{
int nbytes;
/* consume up to 3 bytes from the input data */
if (data_size >= 3) {
ctx->x = AV_RB24(in);
nbytes = 3;
} else if (data_size == 2) {
ctx->x = AV_RB16(in);
nbytes = 2;
} else {
ctx->x = *in;
nbytes = 1;
}
ctx->in_buf = in + nbytes;
ctx->data_size = data_size - nbytes;
ctx->err = 0;
ctx->j = ELS_JOTS_PER_BYTE;
ctx->t = ELS_MAX;
ctx->diff = FFMIN(ELS_MAX - ctx->x,
ELS_MAX - els_exp_tab[ELS_JOTS_PER_BYTE * 4 - 1]);
}
void ff_els_decoder_uninit(ElsUnsignedRung *rung)
{
av_freep(&rung->rem_rung_list);
}
static int els_import_byte(ElsDecCtx *ctx)
{
if (!ctx->data_size) {
ctx->err = AVERROR_EOF;
return AVERROR_EOF;
}
ctx->x = (ctx->x << 8) | *ctx->in_buf++;
ctx->data_size--;
ctx->j += ELS_JOTS_PER_BYTE;
ctx->t <<= 8;
return 0;
}
int ff_els_decode_bit(ElsDecCtx *ctx, uint8_t *rung)
{
int z, bit, ret;
const uint32_t *pAllowable = &els_exp_tab[ELS_JOTS_PER_BYTE * 3];
if (ctx->err)
return 0;
z = pAllowable[ctx->j + Ladder[*rung].ALps];
ctx->t -= z;
ctx->diff -= z;
if (ctx->diff > 0)
return *rung & 1; /* shortcut for x < t > pAllowable[j - 1] */
if (ctx->t > ctx->x) { /* decode most probable symbol (MPS) */
ctx->j += Ladder[*rung].AMps;
while (ctx->t > pAllowable[ctx->j])
ctx->j++;
if (ctx->j <= 0) { /* MPS: import one byte from bytestream. */
ret = els_import_byte(ctx);
if (ret < 0)
return ret;
}
z = ctx->t;
bit = *rung & 1;
*rung = Ladder[*rung].next0;
} else { /* decode less probable symbol (LPS) */
ctx->x -= ctx->t;
ctx->t = z;
ctx->j += Ladder[*rung].ALps;
if (ctx->j <= 0) {
/* LPS: import one byte from bytestream. */
z <<= 8;
ret = els_import_byte(ctx);
if (ret < 0)
return ret;
if (ctx->j <= 0) {
/* LPS: import second byte from bytestream. */
z <<= 8;
ret = els_import_byte(ctx);
if (ret < 0)
return ret;
while (pAllowable[ctx->j - 1] >= z)
ctx->j--;
}
}
bit = !(*rung & 1);
*rung = Ladder[*rung].next1;
}
ctx->diff = FFMIN(z - ctx->x, z - pAllowable[ctx->j - 1]);
return bit;
}
unsigned ff_els_decode_unsigned(ElsDecCtx *ctx, ElsUnsignedRung *ur)
{
int i, n, r, bit;
ElsRungNode *rung_node;
if (ctx->err)
return 0;
/* decode unary prefix */
for (n = 0; n < ELS_EXPGOLOMB_LEN + 1; n++)
if (ff_els_decode_bit(ctx, &ur->prefix_rung[n]))
break;
/* handle the error/overflow case */
if (ctx->err || n >= ELS_EXPGOLOMB_LEN) {
ctx->err = AVERROR_INVALIDDATA;
return 0;
}
/* handle the zero case */
if (!n)
return 0;
/* initialize probability tree */
if (!ur->rem_rung_list) {
ur->rem_rung_list = av_realloc(NULL, RUNG_SPACE);
if (!ur->rem_rung_list) {
ctx->err = AVERROR(ENOMEM);
return 0;
}
memset(ur->rem_rung_list, 0, RUNG_SPACE);
ur->rung_list_size = RUNG_SPACE;
ur->avail_index = ELS_EXPGOLOMB_LEN;
}
/* decode the remainder */
for (i = 0, r = 0, bit = 0; i < n; i++) {
if (!i)
rung_node = &ur->rem_rung_list[n];
else {
if (!rung_node->next_index) {
if (ur->rung_list_size <= (ur->avail_index + 2) * sizeof(ElsRungNode)) {
// remember rung_node position
ptrdiff_t pos = rung_node - ur->rem_rung_list;
ctx->err = av_reallocp(&ur->rem_rung_list,
ur->rung_list_size +
RUNG_SPACE);
if (ctx->err < 0) {
return 0;
}
memset((uint8_t *) ur->rem_rung_list + ur->rung_list_size, 0,
RUNG_SPACE);
ur->rung_list_size += RUNG_SPACE;
// restore rung_node position in the new list
rung_node = &ur->rem_rung_list[pos];
}
rung_node->next_index = ur->avail_index;
ur->avail_index += 2;
}
rung_node = &ur->rem_rung_list[rung_node->next_index + bit];
}
bit = ff_els_decode_bit(ctx, &rung_node->rung);
if (ctx->err)
return bit;
r = (r << 1) + bit;
}
return (1 << n) - 1 + r; /* make value from exp golomb code */
}