/* * 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 */