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ffmpeg/libavcodec/bitstream.c

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/*
* Common bit i/o utils
* Copyright (c) 2000, 2001 Fabrice Bellard
* Copyright (c) 2002-2004 Michael Niedermayer <michaelni@gmx.at>
*
* alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
*
* 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.c
* bitstream api.
*/
#include "avcodec.h"
#include "get_bits.h"
#include "put_bits.h"
const uint8_t ff_log2_run[32]={
0, 0, 0, 0, 1, 1, 1, 1,
2, 2, 2, 2, 3, 3, 3, 3,
4, 4, 5, 5, 6, 6, 7, 7,
8, 9,10,11,12,13,14,15
};
void align_put_bits(PutBitContext *s)
{
#ifdef ALT_BITSTREAM_WRITER
put_bits(s,( - s->index) & 7,0);
#else
put_bits(s,s->bit_left & 7,0);
#endif
}
void ff_put_string(PutBitContext *pb, const char *string, int terminate_string)
{
while(*string){
put_bits(pb, 8, *string);
string++;
}
if(terminate_string)
put_bits(pb, 8, 0);
}
void ff_copy_bits(PutBitContext *pb, const uint8_t *src, int length)
{
int words= length>>4;
int bits= length&15;
int i;
if(length==0) return;
if(CONFIG_SMALL || words < 16 || put_bits_count(pb)&7){
for(i=0; i<words; i++) put_bits(pb, 16, AV_RB16(src + 2*i));
}else{
for(i=0; put_bits_count(pb)&31; i++)
put_bits(pb, 8, src[i]);
flush_put_bits(pb);
memcpy(put_bits_ptr(pb), src+i, 2*words-i);
skip_put_bytes(pb, 2*words-i);
}
put_bits(pb, bits, AV_RB16(src + 2*words)>>(16-bits));
}
/* VLC decoding */
//#define DEBUG_VLC
#define GET_DATA(v, table, i, wrap, size) \
{\
const uint8_t *ptr = (const uint8_t *)table + i * wrap;\
switch(size) {\
case 1:\
v = *(const uint8_t *)ptr;\
break;\
case 2:\
v = *(const uint16_t *)ptr;\
break;\
default:\
v = *(const uint32_t *)ptr;\
break;\
}\
}
static int alloc_table(VLC *vlc, int size, int use_static)
{
int index;
index = vlc->table_size;
vlc->table_size += size;
if (vlc->table_size > vlc->table_allocated) {
if(use_static)
abort(); //cant do anything, init_vlc() is used with too little memory
vlc->table_allocated += (1 << vlc->bits);
vlc->table = av_realloc(vlc->table,
sizeof(VLC_TYPE) * 2 * vlc->table_allocated);
if (!vlc->table)
return -1;
}
return index;
}
static int build_table(VLC *vlc, int table_nb_bits,
int nb_codes,
const void *bits, int bits_wrap, int bits_size,
const void *codes, int codes_wrap, int codes_size,
const void *symbols, int symbols_wrap, int symbols_size,
uint32_t code_prefix, int n_prefix, int flags)
{
int i, j, k, n, table_size, table_index, nb, n1, index, code_prefix2, symbol;
uint32_t code;
VLC_TYPE (*table)[2];
table_size = 1 << table_nb_bits;
table_index = alloc_table(vlc, table_size, flags & INIT_VLC_USE_NEW_STATIC);
#ifdef DEBUG_VLC
av_log(NULL,AV_LOG_DEBUG,"new table index=%d size=%d code_prefix=%x n=%d\n",
table_index, table_size, code_prefix, n_prefix);
#endif
if (table_index < 0)
return -1;
table = &vlc->table[table_index];
for(i=0;i<table_size;i++) {
table[i][1] = 0; //bits
table[i][0] = -1; //codes
}
/* first pass: map codes and compute auxillary table sizes */
for(i=0;i<nb_codes;i++) {
GET_DATA(n, bits, i, bits_wrap, bits_size);
GET_DATA(code, codes, i, codes_wrap, codes_size);
/* we accept tables with holes */
if (n <= 0)
continue;
if (!symbols)
symbol = i;
else
GET_DATA(symbol, symbols, i, symbols_wrap, symbols_size);
#if defined(DEBUG_VLC) && 0
av_log(NULL,AV_LOG_DEBUG,"i=%d n=%d code=0x%x\n", i, n, code);
#endif
/* if code matches the prefix, it is in the table */
n -= n_prefix;
if(flags & INIT_VLC_LE)
code_prefix2= code & (n_prefix>=32 ? 0xffffffff : (1 << n_prefix)-1);
else
code_prefix2= code >> n;
if (n > 0 && code_prefix2 == code_prefix) {
if (n <= table_nb_bits) {
/* no need to add another table */
j = (code << (table_nb_bits - n)) & (table_size - 1);
nb = 1 << (table_nb_bits - n);
for(k=0;k<nb;k++) {
if(flags & INIT_VLC_LE)
j = (code >> n_prefix) + (k<<n);
#ifdef DEBUG_VLC
av_log(NULL, AV_LOG_DEBUG, "%4x: code=%d n=%d\n",
j, i, n);
#endif
if (table[j][1] /*bits*/ != 0) {
av_log(NULL, AV_LOG_ERROR, "incorrect codes\n");
return -1;
}
table[j][1] = n; //bits
table[j][0] = symbol;
j++;
}
} else {
n -= table_nb_bits;
j = (code >> ((flags & INIT_VLC_LE) ? n_prefix : n)) & ((1 << table_nb_bits) - 1);
#ifdef DEBUG_VLC
av_log(NULL,AV_LOG_DEBUG,"%4x: n=%d (subtable)\n",
j, n);
#endif
/* compute table size */
n1 = -table[j][1]; //bits
if (n > n1)
n1 = n;
table[j][1] = -n1; //bits
}
}
}
/* second pass : fill auxillary tables recursively */
for(i=0;i<table_size;i++) {
n = table[i][1]; //bits
if (n < 0) {
n = -n;
if (n > table_nb_bits) {
n = table_nb_bits;
table[i][1] = -n; //bits
}
index = build_table(vlc, n, nb_codes,
bits, bits_wrap, bits_size,
codes, codes_wrap, codes_size,
symbols, symbols_wrap, symbols_size,
(flags & INIT_VLC_LE) ? (code_prefix | (i << n_prefix)) : ((code_prefix << table_nb_bits) | i),
n_prefix + table_nb_bits, flags);
if (index < 0)
return -1;
/* note: realloc has been done, so reload tables */
table = &vlc->table[table_index];
table[i][0] = index; //code
}
}
return table_index;
}
/* Build VLC decoding tables suitable for use with get_vlc().
'nb_bits' set thee decoding table size (2^nb_bits) entries. The
bigger it is, the faster is the decoding. But it should not be too
big to save memory and L1 cache. '9' is a good compromise.
'nb_codes' : number of vlcs codes
'bits' : table which gives the size (in bits) of each vlc code.
'codes' : table which gives the bit pattern of of each vlc code.
'symbols' : table which gives the values to be returned from get_vlc().
'xxx_wrap' : give the number of bytes between each entry of the
'bits' or 'codes' tables.
'xxx_size' : gives the number of bytes of each entry of the 'bits'
or 'codes' tables.
'wrap' and 'size' allows to use any memory configuration and types
(byte/word/long) to store the 'bits', 'codes', and 'symbols' tables.
'use_static' should be set to 1 for tables, which should be freed
with av_free_static(), 0 if free_vlc() will be used.
*/
int init_vlc_sparse(VLC *vlc, int nb_bits, int nb_codes,
const void *bits, int bits_wrap, int bits_size,
const void *codes, int codes_wrap, int codes_size,
const void *symbols, int symbols_wrap, int symbols_size,
int flags)
{
vlc->bits = nb_bits;
if(flags & INIT_VLC_USE_NEW_STATIC){
if(vlc->table_size && vlc->table_size == vlc->table_allocated){
return 0;
}else if(vlc->table_size){
abort(); // fatal error, we are called on a partially initialized table
}
}else {
vlc->table = NULL;
vlc->table_allocated = 0;
vlc->table_size = 0;
}
#ifdef DEBUG_VLC
av_log(NULL,AV_LOG_DEBUG,"build table nb_codes=%d\n", nb_codes);
#endif
if (build_table(vlc, nb_bits, nb_codes,
bits, bits_wrap, bits_size,
codes, codes_wrap, codes_size,
symbols, symbols_wrap, symbols_size,
0, 0, flags) < 0) {
av_freep(&vlc->table);
return -1;
}
if((flags & INIT_VLC_USE_NEW_STATIC) && vlc->table_size != vlc->table_allocated)
av_log(NULL, AV_LOG_ERROR, "needed %d had %d\n", vlc->table_size, vlc->table_allocated);
return 0;
}
void free_vlc(VLC *vlc)
{
av_freep(&vlc->table);
}
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