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/*
* 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 libavcodec/dirac_arith.h
* 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
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 */
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