/* * 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 */ }