mirror of
https://git.videolan.org/git/ffmpeg.git
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278 lines
6.3 KiB
C
278 lines
6.3 KiB
C
/*
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* H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder
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* Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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/**
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* @file
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* Context Adaptive Binary Arithmetic Coder.
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*/
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#ifndef AVCODEC_CABAC_H
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#define AVCODEC_CABAC_H
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#include <stddef.h>
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#include "put_bits.h"
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//#undef NDEBUG
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#include <assert.h>
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#define CABAC_BITS 16
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#define CABAC_MASK ((1<<CABAC_BITS)-1)
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typedef struct CABACContext{
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int low;
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int range;
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int outstanding_count;
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#ifdef STRICT_LIMITS
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int symCount;
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#endif
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const uint8_t *bytestream_start;
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const uint8_t *bytestream;
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const uint8_t *bytestream_end;
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PutBitContext pb;
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}CABACContext;
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extern uint8_t ff_h264_mlps_state[4*64];
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extern uint8_t ff_h264_lps_range[4*2*64]; ///< rangeTabLPS
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extern uint8_t ff_h264_mps_state[2*64]; ///< transIdxMPS
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extern uint8_t ff_h264_lps_state[2*64]; ///< transIdxLPS
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extern const uint8_t ff_h264_norm_shift[512];
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#if ARCH_X86
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# include "x86/cabac.h"
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#endif
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void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size);
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void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size);
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void ff_init_cabac_states(CABACContext *c);
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static inline void put_cabac_bit(CABACContext *c, int b){
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put_bits(&c->pb, 1, b);
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for(;c->outstanding_count; c->outstanding_count--){
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put_bits(&c->pb, 1, 1-b);
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}
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}
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static inline void renorm_cabac_encoder(CABACContext *c){
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while(c->range < 0x100){
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//FIXME optimize
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if(c->low<0x100){
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put_cabac_bit(c, 0);
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}else if(c->low<0x200){
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c->outstanding_count++;
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c->low -= 0x100;
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}else{
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put_cabac_bit(c, 1);
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c->low -= 0x200;
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}
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c->range+= c->range;
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c->low += c->low;
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}
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}
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static void refill(CABACContext *c){
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#if CABAC_BITS == 16
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c->low+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
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#else
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c->low+= c->bytestream[0]<<1;
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#endif
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c->low -= CABAC_MASK;
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c->bytestream+= CABAC_BITS/8;
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}
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static inline void renorm_cabac_decoder(CABACContext *c){
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while(c->range < 0x100){
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c->range+= c->range;
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c->low+= c->low;
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if(!(c->low & CABAC_MASK))
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refill(c);
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}
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}
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static inline void renorm_cabac_decoder_once(CABACContext *c){
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int shift= (uint32_t)(c->range - 0x100)>>31;
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c->range<<= shift;
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c->low <<= shift;
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if(!(c->low & CABAC_MASK))
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refill(c);
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}
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#ifndef get_cabac_inline
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static void refill2(CABACContext *c){
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int i, x;
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x= c->low ^ (c->low-1);
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i= 7 - ff_h264_norm_shift[x>>(CABAC_BITS-1)];
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x= -CABAC_MASK;
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#if CABAC_BITS == 16
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x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);
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#else
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x+= c->bytestream[0]<<1;
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#endif
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c->low += x<<i;
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c->bytestream+= CABAC_BITS/8;
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}
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static av_always_inline int get_cabac_inline(CABACContext *c, uint8_t * const state){
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int s = *state;
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int RangeLPS= ff_h264_lps_range[2*(c->range&0xC0) + s];
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int bit, lps_mask;
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c->range -= RangeLPS;
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lps_mask= ((c->range<<(CABAC_BITS+1)) - c->low)>>31;
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c->low -= (c->range<<(CABAC_BITS+1)) & lps_mask;
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c->range += (RangeLPS - c->range) & lps_mask;
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s^=lps_mask;
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*state= (ff_h264_mlps_state+128)[s];
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bit= s&1;
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lps_mask= ff_h264_norm_shift[c->range];
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c->range<<= lps_mask;
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c->low <<= lps_mask;
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if(!(c->low & CABAC_MASK))
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refill2(c);
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return bit;
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}
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#endif
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static int av_noinline av_unused get_cabac_noinline(CABACContext *c, uint8_t * const state){
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return get_cabac_inline(c,state);
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}
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static int av_unused get_cabac(CABACContext *c, uint8_t * const state){
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return get_cabac_inline(c,state);
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}
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static int av_unused get_cabac_bypass(CABACContext *c){
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int range;
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c->low += c->low;
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if(!(c->low & CABAC_MASK))
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refill(c);
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range= c->range<<(CABAC_BITS+1);
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if(c->low < range){
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return 0;
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}else{
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c->low -= range;
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return 1;
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}
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}
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#ifndef get_cabac_bypass_sign
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static av_always_inline int get_cabac_bypass_sign(CABACContext *c, int val){
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int range, mask;
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c->low += c->low;
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if(!(c->low & CABAC_MASK))
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refill(c);
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range= c->range<<(CABAC_BITS+1);
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c->low -= range;
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mask= c->low >> 31;
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range &= mask;
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c->low += range;
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return (val^mask)-mask;
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}
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#endif
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/**
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*
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* @return the number of bytes read or 0 if no end
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*/
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static int av_unused get_cabac_terminate(CABACContext *c){
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c->range -= 2;
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if(c->low < c->range<<(CABAC_BITS+1)){
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renorm_cabac_decoder_once(c);
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return 0;
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}else{
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return c->bytestream - c->bytestream_start;
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}
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}
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#if 0
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/**
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* Get (truncated) unary binarization.
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*/
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static int get_cabac_u(CABACContext *c, uint8_t * state, int max, int max_index, int truncated){
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int i;
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for(i=0; i<max; i++){
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if(get_cabac(c, state)==0)
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return i;
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if(i< max_index) state++;
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}
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return truncated ? max : -1;
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}
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/**
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* get unary exp golomb k-th order binarization.
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*/
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static int get_cabac_ueg(CABACContext *c, uint8_t * state, int max, int is_signed, int k, int max_index){
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int i, v;
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int m= 1<<k;
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if(get_cabac(c, state)==0)
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return 0;
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if(0 < max_index) state++;
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for(i=1; i<max; i++){
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if(get_cabac(c, state)==0){
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if(is_signed && get_cabac_bypass(c)){
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return -i;
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}else
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return i;
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}
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if(i < max_index) state++;
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}
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while(get_cabac_bypass(c)){
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i+= m;
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m+= m;
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}
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v=0;
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while(m>>=1){
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v+= v + get_cabac_bypass(c);
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}
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i += v;
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if(is_signed && get_cabac_bypass(c)){
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return -i;
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}else
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return i;
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}
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#endif /* 0 */
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#endif /* AVCODEC_CABAC_H */
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