| 1 | /* |
| 2 | * Copyright (C) 2007 Marco Gerards <marco@gnu.org> |
| 3 | * Copyright (C) 2009 David Conrad |
| 4 | * |
| 5 | * This file is part of FFmpeg. |
| 6 | * |
| 7 | * FFmpeg is free software; you can redistribute it and/or |
| 8 | * modify it under the terms of the GNU Lesser General Public |
| 9 | * License as published by the Free Software Foundation; either |
| 10 | * version 2.1 of the License, or (at your option) any later version. |
| 11 | * |
| 12 | * FFmpeg is distributed in the hope that it will be useful, |
| 13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
| 15 | * Lesser General Public License for more details. |
| 16 | * |
| 17 | * You should have received a copy of the GNU Lesser General Public |
| 18 | * License along with FFmpeg; if not, write to the Free Software |
| 19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
| 20 | */ |
| 21 | |
| 22 | /** |
| 23 | * @file |
| 24 | * Arithmetic decoder for Dirac |
| 25 | * @author Marco Gerards <marco@gnu.org> |
| 26 | */ |
| 27 | |
| 28 | #ifndef AVCODEC_DIRAC_ARITH_H |
| 29 | #define AVCODEC_DIRAC_ARITH_H |
| 30 | |
| 31 | #include "libavutil/x86/asm.h" |
| 32 | #include "bytestream.h" |
| 33 | #include "get_bits.h" |
| 34 | |
| 35 | enum dirac_arith_contexts { |
| 36 | CTX_ZPZN_F1, |
| 37 | CTX_ZPNN_F1, |
| 38 | CTX_NPZN_F1, |
| 39 | CTX_NPNN_F1, |
| 40 | CTX_ZP_F2, |
| 41 | CTX_ZP_F3, |
| 42 | CTX_ZP_F4, |
| 43 | CTX_ZP_F5, |
| 44 | CTX_ZP_F6, |
| 45 | CTX_NP_F2, |
| 46 | CTX_NP_F3, |
| 47 | CTX_NP_F4, |
| 48 | CTX_NP_F5, |
| 49 | CTX_NP_F6, |
| 50 | CTX_COEFF_DATA, |
| 51 | CTX_SIGN_NEG, |
| 52 | CTX_SIGN_ZERO, |
| 53 | CTX_SIGN_POS, |
| 54 | CTX_ZERO_BLOCK, |
| 55 | CTX_DELTA_Q_F, |
| 56 | CTX_DELTA_Q_DATA, |
| 57 | CTX_DELTA_Q_SIGN, |
| 58 | |
| 59 | DIRAC_CTX_COUNT |
| 60 | }; |
| 61 | |
| 62 | // Dirac resets the arith decoder between decoding various types of data, |
| 63 | // so many contexts are never used simultaneously. Thus, we can reduce |
| 64 | // the number of contexts needed by reusing them. |
| 65 | #define CTX_SB_F1 CTX_ZP_F5 |
| 66 | #define CTX_SB_DATA 0 |
| 67 | #define CTX_PMODE_REF1 0 |
| 68 | #define CTX_PMODE_REF2 1 |
| 69 | #define CTX_GLOBAL_BLOCK 2 |
| 70 | #define CTX_MV_F1 CTX_ZP_F2 |
| 71 | #define CTX_MV_DATA 0 |
| 72 | #define CTX_DC_F1 CTX_ZP_F5 |
| 73 | #define CTX_DC_DATA 0 |
| 74 | |
| 75 | typedef struct { |
| 76 | unsigned low; |
| 77 | uint16_t range; |
| 78 | int16_t counter; |
| 79 | |
| 80 | const uint8_t *bytestream; |
| 81 | const uint8_t *bytestream_end; |
| 82 | |
| 83 | uint16_t contexts[DIRAC_CTX_COUNT]; |
| 84 | } DiracArith; |
| 85 | |
| 86 | extern const uint8_t ff_dirac_next_ctx[DIRAC_CTX_COUNT]; |
| 87 | extern const uint16_t ff_dirac_prob[256]; |
| 88 | extern int16_t ff_dirac_prob_branchless[256][2]; |
| 89 | |
| 90 | static inline void renorm(DiracArith *c) |
| 91 | { |
| 92 | #if HAVE_FAST_CLZ |
| 93 | int shift = 14 - av_log2_16bit(c->range-1) + ((c->range-1)>>15); |
| 94 | |
| 95 | c->low <<= shift; |
| 96 | c->range <<= shift; |
| 97 | c->counter += shift; |
| 98 | #else |
| 99 | while (c->range <= 0x4000) { |
| 100 | c->low <<= 1; |
| 101 | c->range <<= 1; |
| 102 | c->counter++; |
| 103 | } |
| 104 | #endif |
| 105 | } |
| 106 | |
| 107 | static inline void refill(DiracArith *c) |
| 108 | { |
| 109 | int counter = c->counter; |
| 110 | |
| 111 | if (counter >= 0) { |
| 112 | int new = bytestream_get_be16(&c->bytestream); |
| 113 | |
| 114 | // the spec defines overread bits to be 1, and streams rely on this |
| 115 | if (c->bytestream > c->bytestream_end) { |
| 116 | new |= 0xff; |
| 117 | if (c->bytestream > c->bytestream_end+1) |
| 118 | new |= 0xff00; |
| 119 | |
| 120 | c->bytestream = c->bytestream_end; |
| 121 | } |
| 122 | |
| 123 | c->low += new << counter; |
| 124 | counter -= 16; |
| 125 | } |
| 126 | c->counter = counter; |
| 127 | } |
| 128 | |
| 129 | static inline int dirac_get_arith_bit(DiracArith *c, int ctx) |
| 130 | { |
| 131 | int prob_zero = c->contexts[ctx]; |
| 132 | int range_times_prob, bit; |
| 133 | unsigned low = c->low; |
| 134 | int range = c->range; |
| 135 | |
| 136 | range_times_prob = (c->range * prob_zero) >> 16; |
| 137 | |
| 138 | #if HAVE_FAST_CMOV && HAVE_INLINE_ASM && HAVE_6REGS |
| 139 | low -= range_times_prob << 16; |
| 140 | range -= range_times_prob; |
| 141 | bit = 0; |
| 142 | __asm__( |
| 143 | "cmpl %5, %4 \n\t" |
| 144 | "setae %b0 \n\t" |
| 145 | "cmovb %3, %2 \n\t" |
| 146 | "cmovb %5, %1 \n\t" |
| 147 | : "+q"(bit), "+r"(range), "+r"(low) |
| 148 | : "r"(c->low), "r"(c->low>>16), |
| 149 | "r"(range_times_prob) |
| 150 | ); |
| 151 | #else |
| 152 | bit = (low >> 16) >= range_times_prob; |
| 153 | if (bit) { |
| 154 | low -= range_times_prob << 16; |
| 155 | range -= range_times_prob; |
| 156 | } else { |
| 157 | range = range_times_prob; |
| 158 | } |
| 159 | #endif |
| 160 | |
| 161 | c->contexts[ctx] += ff_dirac_prob_branchless[prob_zero>>8][bit]; |
| 162 | c->low = low; |
| 163 | c->range = range; |
| 164 | |
| 165 | renorm(c); |
| 166 | refill(c); |
| 167 | return bit; |
| 168 | } |
| 169 | |
| 170 | static inline int dirac_get_arith_uint(DiracArith *c, int follow_ctx, int data_ctx) |
| 171 | { |
| 172 | int ret = 1; |
| 173 | while (!dirac_get_arith_bit(c, follow_ctx)) { |
| 174 | if (ret >= 0x40000000) { |
| 175 | av_log(NULL, AV_LOG_ERROR, "dirac_get_arith_uint overflow\n"); |
| 176 | return -1; |
| 177 | } |
| 178 | ret <<= 1; |
| 179 | ret += dirac_get_arith_bit(c, data_ctx); |
| 180 | follow_ctx = ff_dirac_next_ctx[follow_ctx]; |
| 181 | } |
| 182 | return ret-1; |
| 183 | } |
| 184 | |
| 185 | static inline int dirac_get_arith_int(DiracArith *c, int follow_ctx, int data_ctx) |
| 186 | { |
| 187 | int ret = dirac_get_arith_uint(c, follow_ctx, data_ctx); |
| 188 | if (ret && dirac_get_arith_bit(c, data_ctx+1)) |
| 189 | ret = -ret; |
| 190 | return ret; |
| 191 | } |
| 192 | |
| 193 | void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int length); |
| 194 | |
| 195 | #endif /* AVCODEC_DIRAC_ARITH_H */ |