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Code Issues Releases Activity

libmpeg2 style bitstream reader fixes

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Originally committed as revision 1875 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2003-05-14 10:55:59 +00:00
parent 924311cd98
commit 17fb5fd34e
3 changed files with 49 additions and 10 deletions
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26
libavcodec/common.c
View File

@ -140,7 +140,7 @@ void init_get_bits(GetBitContext *s,
#ifdef ALT_BITSTREAM_READER
s->index=0;
#elif defined LIBMPEG2_BITSTREAM_READER
#ifdef LIBMPEG2_BITSTREAM_HACK
#ifdef LIBMPEG2_BITSTREAM_READER_HACK
if ((int)buffer&1) {
/* word alignment */
s->cache = (*buffer++)<<24;
@ -170,6 +170,30 @@ void init_get_bits(GetBitContext *s,
#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;

25
libavcodec/common.h
View File

@ -543,8 +543,8 @@ static inline int get_bits_count(GetBitContext *s){
# define UPDATE_CACHE(name, gb)\
if(name##_bit_count >= 0){\
name##_cache+= (int)be2me_16(*(uint16_t*)name##_buffer_ptr++) << name##_bit_count;\
name##_buffer_ptr+=2;\
name##_cache+= (int)be2me_16(*(uint16_t*)name##_buffer_ptr) << name##_bit_count;\
((uint16_t*)name##_buffer_ptr)++;\
name##_bit_count-= 16;\
}\
@ -654,9 +654,12 @@ static inline int get_bits_count(GetBitContext *s){
#endif
/* add BERO
if MSB not set it is negative
*/
/**
* read mpeg1 dc style vlc (sign bit + mantisse with no MSB).
* if MSB not set it is negative
* @param n length in bits
* @author BERO
*/
static inline int get_xbits(GetBitContext *s, int n){
register int tmp;
register int32_t cache;
@ -685,6 +688,10 @@ static inline int get_sbits(GetBitContext *s, int n){
return tmp;
}
/**
* reads 0-17 bits.
* Note, the alt bitstream reader can read upto 25 bits, but the libmpeg2 reader cant
*/
static inline unsigned int get_bits(GetBitContext *s, int n){
register int tmp;
OPEN_READER(re, s)
@ -695,6 +702,12 @@ static inline unsigned int get_bits(GetBitContext *s, int n){
return tmp;
}
unsigned int get_bits_long(GetBitContext *s, int n);
/**
* shows 0-17 bits.
* Note, the alt bitstream reader can read upto 25 bits, but the libmpeg2 reader cant
*/
static inline unsigned int show_bits(GetBitContext *s, int n){
register int tmp;
OPEN_READER(re, s)
@ -704,6 +717,8 @@ static inline unsigned int show_bits(GetBitContext *s, int n){
return tmp;
}
unsigned int show_bits_long(GetBitContext *s, int n);
static inline void skip_bits(GetBitContext *s, int n){
//Note gcc seems to optimize this to s->index+=n for the ALT_READER :))
OPEN_READER(re, s)

8
libavcodec/h263.c
View File

@ -2708,7 +2708,7 @@ static int mpeg4_decode_partition_a(MpegEncContext *s){
if(s->pict_type==I_TYPE){
int i;
if(show_bits(&s->gb, 19)==DC_MARKER){
if(show_bits_long(&s->gb, 19)==DC_MARKER){
return mb_num-1;
}
@ -2956,7 +2956,7 @@ int ff_mpeg4_decode_partitions(MpegEncContext *s)
s->mb_num_left= mb_num;
if(s->pict_type==I_TYPE){
if(get_bits(&s->gb, 19)!=DC_MARKER){
if(get_bits_long(&s->gb, 19)!=DC_MARKER){
fprintf(stderr, "marker missing after first I partition at %d %d\n", s->mb_x, s->mb_y);
return -1;
}
@ -3885,7 +3885,7 @@ int h263_decode_picture_header(MpegEncContext *s)
int format, width, height;
/* picture start code */
if (get_bits(&s->gb, 22) != 0x20) {
if (get_bits_long(&s->gb, 22) != 0x20) {
fprintf(stderr, "Bad picture start code\n");
return -1;
}
@ -4878,7 +4878,7 @@ int intel_h263_decode_picture_header(MpegEncContext *s)
int format;
/* picture header */
if (get_bits(&s->gb, 22) != 0x20) {
if (get_bits_long(&s->gb, 22) != 0x20) {
fprintf(stderr, "Bad picture start code\n");
return -1;
}