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FFmpeg/libavcodec/common.c
Michael Niedermayer 99683a3077 2 byte shorter userdata for mpeg4 
in the past it was startcode,string,00,7F,startcode
now it is startcode,string,stratcode
both are mpeg4 compliant, as according to the standard the userdata lasts until the next 00 00 01 (startcode prefix) but some very primitive decoders which simply skip until the first 00 byte and then expect the next valid startcode might fail with the old variant, just a theory though (didnt test if quicktime can decode it now)

Originally committed as revision 2767 to svn://svn.ffmpeg.org/ffmpeg/trunk
2004-02-08 22:52:35 +00:00

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/*
* Common bit i/o utils
* Copyright (c) 2000, 2001 Fabrice Bellard.
* Copyright (c) 2002-2004 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., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*
* alternative bitstream reader & writer by Michael Niedermayer <michaelni@gmx.at>
*/
/**
* @file common.c
* common internal api.
*/
#include "avcodec.h"
const uint8_t ff_sqrt_tab[128]={
0, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5,
5, 5, 5, 5, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 6, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9, 9,
9, 9, 9, 9,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,11,11,11,11,11,11,11
};
const uint8_t ff_log2_tab[256]={
0,0,1,1,2,2,2,2,3,3,3,3,3,3,3,3,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,4,
5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,5,
6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,6,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,
7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7,7
};
void init_put_bits(PutBitContext *s, uint8_t *buffer, int 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
}
//#ifdef CONFIG_ENCODERS
#if 1
/* return the number of bits output */
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
}
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
}
#endif //CONFIG_ENCODERS
/* pad the end of the output stream with zeros */
void flush_put_bits(PutBitContext *s)
{
#ifdef ALT_BITSTREAM_WRITER
align_put_bits(s);
#else
s->bit_buf<<= s->bit_left;
while (s->bit_left < 32) {
/* XXX: should test end of buffer */
*s->buf_ptr++=s->bit_buf >> 24;
s->bit_buf<<=8;
s->bit_left+=8;
}
s->bit_left=32;
s->bit_buf=0;
#endif
}
#ifdef CONFIG_ENCODERS
void put_string(PutBitContext * pbc, char *s, int put_zero)
{
while(*s){
put_bits(pbc, 8, *s);
s++;
}
if(put_zero)
put_bits(pbc, 8, 0);
}
/* bit input functions */
#endif //CONFIG_ENCODERS
/**
* init GetBitContext.
* @param buffer bitstream buffer, must be FF_INPUT_BUFFER_PADDING_SIZE bytes larger then the actual read bits
* because some optimized bitstream readers read 32 or 64 bit at once and could read over the end
* @param bit_size the size of the buffer in bits
*/
void init_get_bits(GetBitContext *s,
const uint8_t *buffer, int bit_size)
{
const int buffer_size= (bit_size+7)>>3;
s->buffer= buffer;
s->size_in_bits= bit_size;
s->buffer_end= buffer + buffer_size;
#ifdef ALT_BITSTREAM_READER
s->index=0;
#elif defined LIBMPEG2_BITSTREAM_READER
#ifdef LIBMPEG2_BITSTREAM_READER_HACK
if ((int)buffer&1) {
/* word alignment */
s->cache = (*buffer++)<<24;
s->buffer_ptr = buffer;
s->bit_count = 16-8;
} else
#endif
{
s->buffer_ptr = buffer;
s->bit_count = 16;
s->cache = 0;
}
#elif defined A32_BITSTREAM_READER
s->buffer_ptr = (uint32_t*)buffer;
s->bit_count = 32;
s->cache0 = 0;
s->cache1 = 0;
#endif
{
OPEN_READER(re, s)
UPDATE_CACHE(re, s)
UPDATE_CACHE(re, s)
CLOSE_READER(re, s)
}
#ifdef A32_BITSTREAM_READER
s->cache1 = 0;
#endif
}
/**
* reads 0-32 bits.
*/
unsigned int get_bits_long(GetBitContext *s, int n){
if(n<=17) return get_bits(s, n);
else{
int ret= get_bits(s, 16) << (n-16);
return ret | get_bits(s, n-16);
}
}
/**
* shows 0-32 bits.
*/
unsigned int show_bits_long(GetBitContext *s, int n){
if(n<=17) return show_bits(s, n);
else{
GetBitContext gb= *s;
int ret= get_bits_long(s, n);
*s= gb;
return ret;
}
}
void align_get_bits(GetBitContext *s)
{
int n= (-get_bits_count(s)) & 7;
if(n) skip_bits(s, n);
}
int check_marker(GetBitContext *s, const char *msg)
{
int bit= get_bits1(s);
if(!bit)
av_log(NULL, AV_LOG_INFO, "Marker bit missing %s\n", msg);
return bit;
}
/* 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 index;
index = vlc->table_size;
vlc->table_size += size;
if (vlc->table_size > vlc->table_allocated) {
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,
uint32_t code_prefix, int n_prefix)
{
int i, j, k, n, table_size, table_index, nb, n1, index;
uint32_t code;
VLC_TYPE (*table)[2];
table_size = 1 << table_nb_bits;
table_index = alloc_table(vlc, table_size);
#ifdef DEBUG_VLC
printf("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 defined(DEBUG_VLC) && 0
printf("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 (n > 0 && (code >> n) == 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++) {
#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");
av_abort();
}
table[j][1] = n; //bits
table[j][0] = i; //code
j++;
}
} else {
n -= table_nb_bits;
j = (code >> n) & ((1 << table_nb_bits) - 1);
#ifdef DEBUG_VLC
printf("%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,
(code_prefix << table_nb_bits) | i,
n_prefix + table_nb_bits);
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.
'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' and 'codes' tables.
*/
int init_vlc(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)
{
vlc->bits = nb_bits;
vlc->table = NULL;
vlc->table_allocated = 0;
vlc->table_size = 0;
#ifdef DEBUG_VLC
printf("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,
0, 0) < 0) {
av_free(vlc->table);
return -1;
}
return 0;
}
void free_vlc(VLC *vlc)
{
av_free(vlc->table);
}
int64_t ff_gcd(int64_t a, int64_t b){
if(b) return ff_gcd(b, a%b);
else return a;
}
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