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Diffstat (limited to 'libavcodec/dirac_arith.h')
| -rw-r--r-- | libavcodec/dirac_arith.h | 190 |
1 files changed, 190 insertions, 0 deletions
diff --git a/libavcodec/dirac_arith.h b/libavcodec/dirac_arith.h new file mode 100644 index 0000000..f9a8bba --- /dev/null +++ b/libavcodec/dirac_arith.h @@ -0,0 +1,190 @@ +/* + * Copyright (C) 2007 Marco Gerards <marco@gnu.org> + * Copyright (C) 2009 David Conrad + * + * 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 + * Arithmetic decoder for Dirac + * @author Marco Gerards <marco@gnu.org> + */ + +#ifndef AVCODEC_DIRAC_ARITH_H +#define AVCODEC_DIRAC_ARITH_H + +#include "bytestream.h" +#include "get_bits.h" + +enum dirac_arith_contexts { + CTX_ZPZN_F1, + CTX_ZPNN_F1, + CTX_NPZN_F1, + CTX_NPNN_F1, + CTX_ZP_F2, + CTX_ZP_F3, + CTX_ZP_F4, + CTX_ZP_F5, + CTX_ZP_F6, + CTX_NP_F2, + CTX_NP_F3, + CTX_NP_F4, + CTX_NP_F5, + CTX_NP_F6, + CTX_COEFF_DATA, + CTX_SIGN_NEG, + CTX_SIGN_ZERO, + CTX_SIGN_POS, + CTX_ZERO_BLOCK, + CTX_DELTA_Q_F, + CTX_DELTA_Q_DATA, + CTX_DELTA_Q_SIGN, + + DIRAC_CTX_COUNT +}; + +// Dirac resets the arith decoder between decoding various types of data, +// so many contexts are never used simultaneously. Thus, we can reduce +// the number of contexts needed by reusing them. +#define CTX_SB_F1 CTX_ZP_F5 +#define CTX_SB_DATA 0 +#define CTX_PMODE_REF1 0 +#define CTX_PMODE_REF2 1 +#define CTX_GLOBAL_BLOCK 2 +#define CTX_MV_F1 CTX_ZP_F2 +#define CTX_MV_DATA 0 +#define CTX_DC_F1 CTX_ZP_F5 +#define CTX_DC_DATA 0 + +typedef struct { + unsigned low; + uint16_t range; + int16_t counter; + + const uint8_t *bytestream; + const uint8_t *bytestream_end; + + uint16_t contexts[DIRAC_CTX_COUNT]; +} DiracArith; + +extern const uint8_t ff_dirac_next_ctx[DIRAC_CTX_COUNT]; +extern const uint16_t ff_dirac_prob[256]; +extern int16_t ff_dirac_prob_branchless[256][2]; + +static inline void renorm(DiracArith *c) +{ +#if HAVE_FAST_CLZ + int shift = 14 - av_log2_16bit(c->range-1) + ((c->range-1)>>15); + + c->low <<= shift; + c->range <<= shift; + c->counter += shift; +#else + while (c->range <= 0x4000) { + c->low <<= 1; + c->range <<= 1; + c->counter++; + } +#endif +} + +static inline void refill(DiracArith *c) +{ + int counter = c->counter; + + if (counter >= 0) { + int new = bytestream_get_be16(&c->bytestream); + + // the spec defines overread bits to be 1, and streams rely on this + if (c->bytestream > c->bytestream_end) { + new |= 0xff; + if (c->bytestream > c->bytestream_end+1) + new |= 0xff00; + + c->bytestream = c->bytestream_end; + } + + c->low += new << counter; + counter -= 16; + } + c->counter = counter; +} + +static inline int dirac_get_arith_bit(DiracArith *c, int ctx) +{ + int prob_zero = c->contexts[ctx]; + int range_times_prob, bit; + unsigned low = c->low; + int range = c->range; + + range_times_prob = (c->range * prob_zero) >> 16; + +#if HAVE_FAST_CMOV && HAVE_INLINE_ASM + low -= range_times_prob << 16; + range -= range_times_prob; + bit = 0; + __asm__( + "cmpl %5, %4 \n\t" + "setae %b0 \n\t" + "cmovb %3, %2 \n\t" + "cmovb %5, %1 \n\t" + : "+q"(bit), "+r"(range), "+r"(low) + : "r"(c->low), "r"(c->low>>16), + "r"(range_times_prob) + ); +#else + bit = (low >> 16) >= range_times_prob; + if (bit) { + low -= range_times_prob << 16; + range -= range_times_prob; + } else { + range = range_times_prob; + } +#endif + + c->contexts[ctx] += ff_dirac_prob_branchless[prob_zero>>8][bit]; + c->low = low; + c->range = range; + + renorm(c); + refill(c); + return bit; +} + +static inline int dirac_get_arith_uint(DiracArith *c, int follow_ctx, int data_ctx) +{ + int ret = 1; + while (!dirac_get_arith_bit(c, follow_ctx)) { + ret <<= 1; + ret += dirac_get_arith_bit(c, data_ctx); + follow_ctx = ff_dirac_next_ctx[follow_ctx]; + } + return ret-1; +} + +static inline int dirac_get_arith_int(DiracArith *c, int follow_ctx, int data_ctx) +{ + int ret = dirac_get_arith_uint(c, follow_ctx, data_ctx); + if (ret && dirac_get_arith_bit(c, data_ctx+1)) + ret = -ret; + return ret; +} + +void ff_dirac_init_arith_decoder(DiracArith *c, GetBitContext *gb, int length); + +#endif /* AVCODEC_DIRAC_ARITH_H */ |
