| /* |
| * 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 "avcodec.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_free(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; |
| ur->rem_rung_list = av_realloc(ur->rem_rung_list, |
| ur->rung_list_size + |
| RUNG_SPACE); |
| if (!ur->rem_rung_list) { |
| av_free(ur->rem_rung_list); |
| ctx->err = AVERROR(ENOMEM); |
| 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 */ |
| } |
