bitstream.h

播放H264文件的播放器

/*
 * copyright (c) 2004 Michael Niedermayer <[e-mail]>
 *
 * 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/bitstream.h
 * bitstream api header.
 */

#ifndef AVCODEC_BITSTREAM_H
#define AVCODEC_BITSTREAM_H

#include <stdlib.h>
#include <assert.h>
#include "libavutil/bswap.h"
#include "libavutil/common.h"
#include "libavutil/intreadwrite.h"
#include "libavutil/log.h"

#if defined(ALT_BITSTREAM_READER_LE) && !defined(ALT_BITSTREAM_READER)
#   define ALT_BITSTREAM_READER
#endif

//#define ALT_BITSTREAM_WRITER
//#define ALIGNED_BITSTREAM_WRITER
#if !defined(LIBMPEG2_BITSTREAM_READER) && !defined(A32_BITSTREAM_READER) && !defined(ALT_BITSTREAM_READER)
#   if ARCH_ARM
#       define A32_BITSTREAM_READER
#   else
#       define ALT_BITSTREAM_READER
//#define LIBMPEG2_BITSTREAM_READER
//#define A32_BITSTREAM_READER
#   endif
#endif

extern const uint8_t ff_reverse[256];

#if ARCH_X86
// avoid +32 for shift optimization (gcc should do that ...)
static _inline  int32_t NEG_SSR32( int32_t a, int8_t s){
    __asm__ ("sarl %1, %0\n\t"
         : "+r" (a)
         : "ic" ((uint8_t)(-s))
    );
    return a;
}
static _inline uint32_t NEG_USR32(uint32_t a, int8_t s){
    __asm__ ("shrl %1, %0\n\t"
         : "+r" (a)
         : "ic" ((uint8_t)(-s))
    );
    return a;
}
#else
#    define NEG_SSR32(a,s) ((( int32_t)(a))>>(32-(s)))
#    define NEG_USR32(a,s) (((uint32_t)(a))>>(32-(s)))
#endif

/* bit output */

/* buf and buf_end must be present and used by every alternative writer. */
typedef struct PutBitContext {
#ifdef ALT_BITSTREAM_WRITER
    uint8_t *buf, *buf_end;
    int index;
#else
    uint32_t bit_buf;
    int bit_left;
    uint8_t *buf, *buf_ptr, *buf_end;
#endif
    int size_in_bits;
} PutBitContext;

static _inline void init_put_bits(PutBitContext *s, uint8_t *buffer, int buffer_size)
{
    if(buffer_size < 0) {
        buffer_size = 0;
        buffer = NULL;
    }

    s->size_in_bits= 8*buffer_size;
    s->buf = buffer;
    s->buf_end = s->buf + buffer_size;
#ifdef ALT_BITSTREAM_WRITER
    s->index=0;
    ((uint32_t*)(s->buf))[0]=0;
//    memset(buffer, 0, buffer_size);
#else
    s->buf_ptr = s->buf;
    s->bit_left=32;
    s->bit_buf=0;
#endif
}

/* return the number of bits output */
static _inline int put_bits_count(PutBitContext *s)
{
#ifdef ALT_BITSTREAM_WRITER
    return s->index;
#else
    return (s->buf_ptr - s->buf) * 8 + 32 - s->bit_left;
#endif
}

/* pad the end of the output stream with zeros */
static _inline void flush_put_bits(PutBitContext *s)
{
#ifdef ALT_BITSTREAM_WRITER
    align_put_bits(s);
#else
#ifndef BITSTREAM_WRITER_LE
    s->bit_buf<<= s->bit_left;
#endif
    while (s->bit_left < 32) {
        /* XXX: should test end of buffer */
#ifdef BITSTREAM_WRITER_LE
        *s->buf_ptr++=s->bit_buf;
        s->bit_buf>>=8;
#else
        *s->buf_ptr++=s->bit_buf >> 24;
        s->bit_buf<<=8;
#endif
        s->bit_left+=8;
    }
    s->bit_left=32;
    s->bit_buf=0;
#endif
}

void align_put_bits(PutBitContext *s);
void ff_put_string(PutBitContext * pbc, const char *s, int put_zero);
void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length);

/* bit input */
/* buffer, buffer_end and size_in_bits must be present and used by every reader */
typedef struct GetBitContext {
    const uint8_t *buffer, *buffer_end;
#ifdef ALT_BITSTREAM_READER
    int index;
#elif defined LIBMPEG2_BITSTREAM_READER
    uint8_t *buffer_ptr;
    uint32_t cache;
    int bit_count;
#elif defined A32_BITSTREAM_READER
    uint32_t *buffer_ptr;
    uint32_t cache0;
    uint32_t cache1;
    int bit_count;
#endif
    int size_in_bits;
} GetBitContext;

#define VLC_TYPE int16_t

typedef struct VLC {
    int bits;
    VLC_TYPE (*table)[2]; ///< code, bits
    int table_size, table_allocated;
} VLC;

typedef struct RL_VLC_ELEM {
    int16_t level;
    int8_t len;
    uint8_t run;
} RL_VLC_ELEM;

#ifndef ALT_BITSTREAM_WRITER
static _inline void put_bits(PutBitContext *s, int n, unsigned int value)
{
    unsigned int bit_buf;
    int bit_left;

    //    printf("put_bits=%d %x\n", n, value);
    assert(n == 32 || value < (1U << n));

    bit_buf = s->bit_buf;
    bit_left = s->bit_left;

    //    printf("n=%d value=%x cnt=%d buf=%x\n", n, value, bit_cnt, bit_buf);
    /* XXX: optimize */
#ifdef BITSTREAM_WRITER_LE
    bit_buf |= value << (32 - bit_left);
    if (n >= bit_left) {
#if !HAVE_FAST_UNALIGNED
        if (3 & (intptr_t) s->buf_ptr) {
            AV_WL32(s->buf_ptr, bit_buf);
        } else
#endif
        *(uint32_t *)s->buf_ptr = le2me_32(bit_buf);
        s->buf_ptr+=4;
        bit_buf = (bit_left==32)?0:value >> bit_left;
        bit_left+=32;
    }
    bit_left-=n;
#else
    if (n < bit_left) {
        bit_buf = (bit_buf<<n) | value;
        bit_left-=n;
    } else {
        bit_buf<<=bit_left;
        bit_buf |= value >> (n - bit_left);
#if !HAVE_FAST_UNALIGNED
        if (3 & (intptr_t) s->buf_ptr) {
            AV_WB32(s->buf_ptr, bit_buf);
        } else
#endif
        *(uint32_t *)s->buf_ptr = be2me_32(bit_buf);
        //printf("bitbuf = %08x\n", bit_buf);
        s->buf_ptr+=4;
        bit_left+=32 - n;
        bit_buf = value;
    }
#endif

    s->bit_buf = bit_buf;
    s->bit_left = bit_left;
}
#endif


#ifdef ALT_BITSTREAM_WRITER
static _inline void put_bits(PutBitContext *s, int n, unsigned int value)
{
#    ifdef ALIGNED_BITSTREAM_WRITER
#        if ARCH_X86
    __asm__ volatile(
        "movl %0, %%ecx                 \n\t"
        "xorl %%eax, %%eax              \n\t"
        "shrdl %%cl, %1, %%eax          \n\t"
        "shrl %%cl, %1                  \n\t"
        "movl %0, %%ecx                 \n\t"
        "shrl $3, %%ecx                 \n\t"
        "andl $0xFFFFFFFC, %%ecx        \n\t"
        "bswapl %1                      \n\t"
        "orl %1, (%2, %%ecx)            \n\t"
        "bswapl %%eax                   \n\t"
        "addl %3, %0                    \n\t"
        "movl %%eax, 4(%2, %%ecx)       \n\t"
        : "=&r" (s->index), "=&r" (value)
        : "r" (s->buf), "r" (n), "0" (s->index), "1" (value<<(-n))
        : "%eax", "%ecx"
    );
#        else
    int index= s->index;
    uint32_t *ptr= ((uint32_t *)s->buf)+(index>>5);

    value<<= 32-n;

    ptr[0] |= be2me_32(value>>(index&31));
    ptr[1]  = be2me_32(value<<(32-(index&31)));
//if(n>24) printf("%d %d\n", n, value);
    index+= n;
    s->index= index;
#        endif
#    else //ALIGNED_BITSTREAM_WRITER
#        if ARCH_X86
    __asm__ volatile(
        "movl $7, %%ecx                 \n\t"
        "andl %0, %%ecx                 \n\t"
        "addl %3, %%ecx                 \n\t"
        "negl %%ecx                     \n\t"
        "shll %%cl, %1                  \n\t"
        "bswapl %1                      \n\t"
        "movl %0, %%ecx                 \n\t"
        "shrl $3, %%ecx                 \n\t"
        "orl %1, (%%ecx, %2)            \n\t"
        "addl %3, %0                    \n\t"
        "movl $0, 4(%%ecx, %2)          \n\t"
        : "=&r" (s->index), "=&r" (value)
        : "r" (s->buf), "r" (n), "0" (s->index), "1" (value)
        : "%ecx"
    );
#        else
    int index= s->index;
    uint32_t *ptr= (uint32_t*)(((uint8_t *)s->buf)+(index>>3));

    ptr[0] |= be2me_32(value<<(32-n-(index&7) ));
    ptr[1] = 0;
//if(n>24) printf("%d %d\n", n, value);
    index+= n;
    s->index= index;
#        endif
#    endif //!ALIGNED_BITSTREAM_WRITER
}
#endif

static _inline void put_sbits(PutBitContext *pb, int bits, int32_t val)
{
    assert(bits >= 0 && bits <= 31);

    put_bits(pb, bits, val & ((1<<bits)-1));
}


static _inline uint8_t* pbBufPtr(PutBitContext *s)
{
#ifdef ALT_BITSTREAM_WRITER
        return s->buf + (s->index>>3);
#else
        return s->buf_ptr;
#endif
}

/**
 *
 * PutBitContext must be flushed & aligned to a byte boundary before calling this.
 */
static _inline void skip_put_bytes(PutBitContext *s, int n){
        assert((put_bits_count(s)&7)==0);
#ifdef ALT_BITSTREAM_WRITER
        FIXME may need some cleaning of the buffer
        s->index += n<<3;
#else
        assert(s->bit_left==32);
        s->buf_ptr += n;
#endif
}

/**
 * Skips the given number of bits.
 * Must only be used if the actual values in the bitstream do not matter.
 */
static _inline void skip_put_bits(PutBitContext *s, int n){
#ifdef ALT_BITSTREAM_WRITER
    s->index += n;
#else
    s->bit_left -= n;
    s->buf_ptr-= s->bit_left>>5;
    s->bit_left &= 31;
#endif
}

/**
 * Changes the end of the buffer.
 */
static _inline void set_put_bits_buffer_size(PutBitContext *s, int size){
    s->buf_end= s->buf + size;
}

/* Bitstream reader API docs:
name
    arbitrary name which is used as prefix for the internal variables

gb
    getbitcontext

OPEN_READER(name, gb)
    loads gb into local variables

CLOSE_READER(name, gb)
    stores local vars in gb

UPDATE_CACHE(name, gb)
    refills the internal cache from the bitstream
    after this call at least MIN_CACHE_BITS will be available,

GET_CACHE(name, gb)
    will output the contents of the internal cache, next bit is MSB of 32 or 64 bit (FIXME 64bit)

SHOW_UBITS(name, gb, num)
    will return the next num bits

SHOW_SBITS(name, gb, num)
    will return the next num bits and do sign extension

SKIP_BITS(name, gb, num)
    will skip over the next num bits
    note, this is equivalent to SKIP_CACHE; SKIP_COUNTER

SKIP_CACHE(name, gb, num)
    will remove the next num bits from the cache (note SKIP_COUNTER MUST be called before UPDATE_CACHE / CLOSE_READER)

SKIP_COUNTER(name, gb, num)
    will increment the internal bit counter (see SKIP_CACHE & SKIP_BITS)

LAST_SKIP_CACHE(name, gb, num)
    will remove the next num bits from the cache if it is needed for UPDATE_CACHE otherwise it will do nothing

LAST_SKIP_BITS(name, gb, num)
    is equivalent to SKIP_LAST_CACHE; SKIP_COUNTER

for examples see get_bits, show_bits, skip_bits, get_vlc
*/

#ifdef ALT_BITSTREAM_READER
#   define MIN_CACHE_BITS 25

#   define OPEN_READER(name, gb)\
        int name##_index= (gb)->index;\
        int name##_cache= 0;\

#   define CLOSE_READER(name, gb)\
        (gb)->index= name##_index;\

# ifdef ALT_BITSTREAM_READER_LE
#   define UPDATE_CACHE(name, gb)\
        name##_cache= AV_RL32( ((const uint8_t *)(gb)->buffer)+(name##_index>>3) ) >> (name##_index&0x07);\

#   define SKIP_CACHE(name, gb, num)\
        name##_cache >>= (num);
# else
#   define UPDATE_CACHE(name, gb)\
        name##_cache= AV_RB32( ((const uint8_t *)(gb)->buffer)+(name##_index>>3) ) << (name##_index&0x07);\

#   define SKIP_CACHE(name, gb, num)\
        name##_cache <<= (num);
# endif

// FIXME name?
#   define SKIP_COUNTER(name, gb, num)\
        name##_index += (num);\

#   define SKIP_BITS(name, gb, num)\
        {\
            SKIP_CACHE(name, gb, num)\
            SKIP_COUNTER(name, gb, num)\
        }\

#   define LAST_SKIP_BITS(name, gb, num) SKIP_COUNTER(name, gb, num)
#   define LAST_SKIP_CACHE(name, gb, num) ;

# ifdef ALT_BITSTREAM_READER_LE
#   define SHOW_UBITS(name, gb, num)\
        ((name##_cache) & (NEG_USR32(0xffffffff,num)))

#   define SHOW_SBITS(name, gb, num)\
        NEG_SSR32((name##_cache)<<(32-(num)), num)
# else
#   define SHOW_UBITS(name, gb, num)\
        NEG_USR32(name##_cache, num)

#   define SHOW_SBITS(name, gb, num)\
        NEG_SSR32(name##_cache, num)
# endif

#   define GET_CACHE(name, gb)\
        ((uint32_t)name##_cache)

static _inline int get_bits_count(GetBitContext *s){
    return s->index;
}

static _inline void skip_bits_long(GetBitContext *s, int n){
    s->index += n;
}

#elif defined LIBMPEG2_BITSTREAM_READER
//libmpeg2 like reader

#   define MIN_CACHE_BITS 17

#   define OPEN_READER(name, gb)\
        int name##_bit_count=(gb)->bit_count;\
        int name##_cache= (gb)->cache;\
        uint8_t * name##_buffer_ptr=(gb)->buffer_ptr;\

#   define CLOSE_READER(name, gb)\
        (gb)->bit_count= name##_bit_count;\
        (gb)->cache= name##_cache;\