PeerStreamer

/*

 * H.26L/H.264/AVC/JVT/14496-10/... encoder/decoder

 * Copyright (c) 2003 Michael Niedermayer <michaelni@gmx.at>

 *

 * This library 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 of the License, or (at your option) any later version.

 *

 * This library 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 this library; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA

 *

 */

/**

 * @file cabac.h

 * Context Adaptive Binary Arithmetic Coder.

 */

#undef NDEBUG

#include <assert.h>

#define CABAC_BITS 8

#define CABAC_MASK ((1<<CABAC_BITS)-1)

typedef struct CABACContext{

    int low;

    int range;

    int outstanding_count;

#ifdef STRICT_LIMITS

    int symCount;

#endif

    uint8_t lps_range[2*65][4];   ///< rangeTabLPS

    uint8_t lps_state[2*64];      ///< transIdxLPS

    uint8_t mps_state[2*64];      ///< transIdxMPS

    const uint8_t *bytestream_start;

    const uint8_t *bytestream;

    const uint8_t *bytestream_end;

    PutBitContext pb;

}CABACContext;

extern const uint8_t ff_h264_lps_range[64][4];

extern const uint8_t ff_h264_mps_state[64];

extern const uint8_t ff_h264_lps_state[64];

extern const uint8_t ff_h264_norm_shift[256];

void ff_init_cabac_encoder(CABACContext *c, uint8_t *buf, int buf_size);

void ff_init_cabac_decoder(CABACContext *c, const uint8_t *buf, int buf_size);

void ff_init_cabac_states(CABACContext *c, uint8_t const (*lps_range)[4],

                          uint8_t const *mps_state, uint8_t const *lps_state, int state_count);

static inline void put_cabac_bit(CABACContext *c, int b){

    put_bits(&c->pb, 1, b);

    for(;c->outstanding_count; c->outstanding_count--){

        put_bits(&c->pb, 1, 1-b);

    }

}

static inline void renorm_cabac_encoder(CABACContext *c){

    while(c->range < 0x100){

        //FIXME optimize

        if(c->low<0x100){

            put_cabac_bit(c, 0);

        }else if(c->low<0x200){

            c->outstanding_count++;

            c->low -= 0x100;

        }else{

            put_cabac_bit(c, 1);

            c->low -= 0x200;

        }

        c->range+= c->range;

        c->low += c->low;

    }

}

static inline void put_cabac(CABACContext *c, uint8_t * const state, int bit){

    int RangeLPS= c->lps_range[*state][c->range>>6];

    if(bit == ((*state)&1)){

        c->range -= RangeLPS;

        *state= c->mps_state[*state];

    }else{

        c->low += c->range - RangeLPS;

        c->range = RangeLPS;

        *state= c->lps_state[*state];

    }

    renorm_cabac_encoder(c);

#ifdef STRICT_LIMITS

    c->symCount++;

#endif

}

static inline void put_cabac_static(CABACContext *c, int RangeLPS, int bit){

    assert(c->range > RangeLPS);

    if(!bit){

        c->range -= RangeLPS;

    }else{

        c->low += c->range - RangeLPS;

        c->range = RangeLPS;

    }

    renorm_cabac_encoder(c);

#ifdef STRICT_LIMITS

    c->symCount++;

#endif

}

/**

 * @param bit 0 -> write zero bit, !=0 write one bit

 */

static inline void put_cabac_bypass(CABACContext *c, int bit){

    c->low += c->low;

    if(bit){

        c->low += c->range;

    }

//FIXME optimize

    if(c->low<0x200){

        put_cabac_bit(c, 0);

    }else if(c->low<0x400){

        c->outstanding_count++;

        c->low -= 0x200;

    }else{

        put_cabac_bit(c, 1);

        c->low -= 0x400;

    }

#ifdef STRICT_LIMITS

    c->symCount++;

#endif

}

/**

 *

 * @return the number of bytes written

 */

static inline int put_cabac_terminate(CABACContext *c, int bit){

    c->range -= 2;

    if(!bit){

        renorm_cabac_encoder(c);

    }else{

        c->low += c->range;

        c->range= 2;

        renorm_cabac_encoder(c);

        assert(c->low <= 0x1FF);

        put_cabac_bit(c, c->low>>9);

        put_bits(&c->pb, 2, ((c->low>>7)&3)|1);

        flush_put_bits(&c->pb); //FIXME FIXME FIXME XXX wrong

    }

#ifdef STRICT_LIMITS

    c->symCount++;

#endif

    return (put_bits_count(&c->pb)+7)>>3;

}

/**

 * put (truncated) unary binarization.

 */

static inline void put_cabac_u(CABACContext *c, uint8_t * state, int v, int max, int max_index, int truncated){

    int i;

    assert(v <= max);

#if 1

    for(i=0; i<v; i++){

        put_cabac(c, state, 1);

        if(i < max_index) state++;

    }

    if(truncated==0 || v<max)

        put_cabac(c, state, 0);

#else

    if(v <= max_index){

        for(i=0; i<v; i++){

            put_cabac(c, state+i, 1);

        }

        if(truncated==0 || v<max)

            put_cabac(c, state+i, 0);

    }else{

        for(i=0; i<=max_index; i++){

            put_cabac(c, state+i, 1);

        }

        for(; i<v; i++){

            put_cabac(c, state+max_index, 1);

        }

        if(truncated==0 || v<max)

            put_cabac(c, state+max_index, 0);

    }

#endif

}

/**

 * put unary exp golomb k-th order binarization.

 */

static inline void put_cabac_ueg(CABACContext *c, uint8_t * state, int v, int max, int is_signed, int k, int max_index){

    int i;

    if(v==0)

        put_cabac(c, state, 0);

    else{

        const int sign= v < 0;

        if(is_signed) v= ABS(v);

        if(v<max){

            for(i=0; i<v; i++){

                put_cabac(c, state, 1);

                if(i < max_index) state++;

            }

            put_cabac(c, state, 0);

        }else{

            int m= 1<<k;

            for(i=0; i<max; i++){

                put_cabac(c, state, 1);

                if(i < max_index) state++;

            }

            v -= max;

            while(v >= m){ //FIXME optimize

                put_cabac_bypass(c, 1);

                v-= m;

                m+= m;

            }

            put_cabac_bypass(c, 0);

            while(m>>=1){

                put_cabac_bypass(c, v&m);

            }

        }

        if(is_signed)

            put_cabac_bypass(c, sign);

    }

}

static void refill(CABACContext *c){

    if(c->bytestream <= c->bytestream_end)

#if CABAC_BITS == 16

        c->low+= ((c->bytestream[0]<<9) + (c->bytestream[1])<<1);

#else

        c->low+= c->bytestream[0]<<1;

#endif

    c->low -= CABAC_MASK;

    c->bytestream+= CABAC_BITS/8;

}

#if 0 /* all use commented */

static void refill2(CABACContext *c){

    int i, x;

    x= c->low ^ (c->low-1);

    i= 8 - ff_h264_norm_shift[x>>(CABAC_BITS+1)];

    x= -CABAC_MASK;

    if(c->bytestream < c->bytestream_end)

#if CABAC_BITS == 16

        x+= (c->bytestream[0]<<9) + (c->bytestream[1]<<1);

#else

        x+= c->bytestream[0]<<1;

#endif

    c->low += x<<i;

    c->bytestream+= CABAC_BITS/8;

}

#endif

static inline void renorm_cabac_decoder(CABACContext *c){

    while(c->range < (0x200 << CABAC_BITS)){

        c->range+= c->range;

        c->low+= c->low;

        if(!(c->low & CABAC_MASK))

            refill(c);

    }

}

static inline void renorm_cabac_decoder_once(CABACContext *c){

    int mask= (c->range - (0x200 << CABAC_BITS))>>31;

    c->range+= c->range&mask;

    c->low  += c->low  &mask;

    if(!(c->low & CABAC_MASK))

        refill(c);

}

static inline int get_cabac(CABACContext *c, uint8_t * const state){

    int RangeLPS= c->lps_range[*state][c->range>>(CABAC_BITS+7)]<<(CABAC_BITS+1);

    int bit, lps_mask attribute_unused;

    c->range -= RangeLPS;

#if 1

    if(c->low < c->range){

        bit= (*state)&1;

        *state= c->mps_state[*state];

        renorm_cabac_decoder_once(c);

    }else{

//        int shift= ff_h264_norm_shift[RangeLPS>>17];

        bit= ((*state)&1)^1;

        c->low -= c->range;

        *state= c->lps_state[*state];

        c->range = RangeLPS;

        renorm_cabac_decoder(c);

/*        c->range = RangeLPS<<shift;

        c->low <<= shift;

        if(!(c->low & 0xFFFF)){

            refill2(c);

        }*/

    }

#else

    lps_mask= (c->range - c->low)>>31;

    c->low -= c->range & lps_mask;

    c->range += (RangeLPS - c->range) & lps_mask;

    bit= ((*state)^lps_mask)&1;

    *state= c->mps_state[(*state) - (128&lps_mask)];

    lps_mask= ff_h264_norm_shift[c->range>>(CABAC_BITS+2)];

    c->range<<= lps_mask;

    c->low  <<= lps_mask;

    if(!(c->low & CABAC_MASK))

        refill2(c);

#endif

    return bit;

}

static inline int get_cabac_bypass(CABACContext *c){

    c->low += c->low;

    if(!(c->low & CABAC_MASK))

        refill(c);

    if(c->low < c->range){

        return 0;

    }else{

        c->low -= c->range;

        return 1;

    }

}

/**

 *

 * @return the number of bytes read or 0 if no end

 */

static inline int get_cabac_terminate(CABACContext *c){

    c->range -= 4<<CABAC_BITS;

    if(c->low < c->range){

        renorm_cabac_decoder_once(c);

        return 0;

    }else{

        return c->bytestream - c->bytestream_start;

    }

}

/**

 * get (truncated) unnary binarization.

 */

static inline int get_cabac_u(CABACContext *c, uint8_t * state, int max, int max_index, int truncated){

    int i;

    for(i=0; i<max; i++){

        if(get_cabac(c, state)==0)

            return i;

        if(i< max_index) state++;

    }

    return truncated ? max : -1;

}

/**

 * get unary exp golomb k-th order binarization.

 */

static inline int get_cabac_ueg(CABACContext *c, uint8_t * state, int max, int is_signed, int k, int max_index){

    int i, v;

    int m= 1<<k;

    if(get_cabac(c, state)==0)

        return 0;

    if(0 < max_index) state++;

    for(i=1; i<max; i++){

        if(get_cabac(c, state)==0){

            if(is_signed && get_cabac_bypass(c)){

                return -i;

            }else

                return i;

        }

        if(i < max_index) state++;

    }

    while(get_cabac_bypass(c)){

        i+= m;

        m+= m;

    }

    v=0;

    while(m>>=1){

        v+= v + get_cabac_bypass(c);

    }

    i += v;

    if(is_signed && get_cabac_bypass(c)){

        return -i;

    }else

        return i;

}