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/*
* Copyright (C) 2006 Aurelien Jacobs <aurel@gnuage.org>
*
* 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
* Common VP5-VP9 range decoder stuff
*/
#ifndef AVCODEC_VPX_RAC_H
#define AVCODEC_VPX_RAC_H
#include <stdint.h>
#include "config.h"
#include "libavutil/attributes.h"
#include "bytestream.h"
typedef struct VPXRangeCoder {
int high;
int bits; /* stored negated (i.e. negative "bits" is a positive number of
bits left) in order to eliminate a negate in cache refilling */
const uint8_t *buffer;
const uint8_t *end;
unsigned int code_word;
int end_reached;
} VPXRangeCoder;
extern const uint8_t ff_vpx_norm_shift[256];
int ff_vpx_init_range_decoder(VPXRangeCoder *c, const uint8_t *buf, int buf_size);
/**
* returns 1 if the end of the stream has been reached, 0 otherwise.
*/
static av_always_inline int vpx_rac_is_end(VPXRangeCoder *c)
{
if (c->end <= c->buffer && c->bits >= 0)
c->end_reached ++;
return c->end_reached > 10;
}
static av_always_inline unsigned int vpx_rac_renorm(VPXRangeCoder *c)
{
int shift = ff_vpx_norm_shift[c->high];
int bits = c->bits;
unsigned int code_word = c->code_word;
c->high <<= shift;
code_word <<= shift;
bits += shift;
if(bits >= 0 && c->buffer < c->end) {
code_word |= bytestream_get_be16(&c->buffer) << bits;
bits -= 16;
}
c->bits = bits;
return code_word;
}
#if ARCH_ARM
#include "arm/vpx_arith.h"
#elif ARCH_X86
#include "x86/vpx_arith.h"
#endif
#ifndef vpx_rac_get_prob
#define vpx_rac_get_prob vpx_rac_get_prob
static av_always_inline int vpx_rac_get_prob(VPXRangeCoder *c, uint8_t prob)
{
unsigned int code_word = vpx_rac_renorm(c);
unsigned int low = 1 + (((c->high - 1) * prob) >> 8);
unsigned int low_shift = low << 16;
int bit = code_word >= low_shift;
c->high = bit ? c->high - low : low;
c->code_word = bit ? code_word - low_shift : code_word;
return bit;
}
#endif
#ifndef vpx_rac_get_prob_branchy
// branchy variant, to be used where there's a branch based on the bit decoded
static av_always_inline int vpx_rac_get_prob_branchy(VPXRangeCoder *c, int prob)
{
unsigned long code_word = vpx_rac_renorm(c);
unsigned low = 1 + (((c->high - 1) * prob) >> 8);
unsigned low_shift = low << 16;
if (code_word >= low_shift) {
c->high -= low;
c->code_word = code_word - low_shift;
return 1;
}
c->high = low;
c->code_word = code_word;
return 0;
}
#endif
static av_always_inline int vpx_rac_get(VPXRangeCoder *c)
{
unsigned int code_word = vpx_rac_renorm(c);
/* equiprobable */
int low = (c->high + 1) >> 1;
unsigned int low_shift = low << 16;
int bit = code_word >= low_shift;
if (bit) {
c->high -= low;
code_word -= low_shift;
} else {
c->high = low;
}
c->code_word = code_word;
return bit;
}
#endif /* AVCODEC_VPX_RAC_H */
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