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optimized encode_dc() (+2% speed on P3 for mpeg1 intra only encodings)

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Originally committed as revision 298 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Michael Niedermayer 2002-02-13 15:26:28 +00:00
parent 80feb2a23e
commit f004ca1c1b
2 changed files with 34 additions and 11 deletions
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41
libavcodec/mpeg12.c
View File

@ -33,6 +33,8 @@
#define EXT_START_CODE 0x000001b5
#define USER_START_CODE 0x000001b2
#define ABS(a) ((a)<0 ? -(a) : (a))
static void mpeg1_encode_block(MpegEncContext *s,
DCTELEM *block,
int component);
@ -196,6 +198,26 @@ void mpeg1_encode_picture_header(MpegEncContext *s, int picture_number)
mpeg1_max_level[0][i]= rl_mpeg1.max_level[0][i];
mpeg1_index_run[0][i]= rl_mpeg1.index_run[0][i];
}
/* build unified dc encoding tables */
for(i=-255; i<256; i++)
{
int adiff, index;
int bits, code;
int diff=i;
adiff = ABS(diff);
if(diff<0) diff--;
index = vlc_dc_table[adiff];
bits= vlc_dc_lum_bits[index] + index;
code= (vlc_dc_lum_code[index]<<index) + (diff & ((1 << index) - 1));
mpeg1_lum_dc_uni[i+255]= bits + (code<<8);
bits= vlc_dc_chroma_bits[index] + index;
code= (vlc_dc_chroma_code[index]<<index) + (diff & ((1 << index) - 1));
mpeg1_chr_dc_uni[i+255]= bits + (code<<8);
}
}
mpeg1_encode_sequence_header(s);
@ -333,19 +355,16 @@ static void mpeg1_encode_motion(MpegEncContext *s, int val)
static inline void encode_dc(MpegEncContext *s, int diff, int component)
{
int adiff, index;
adiff = abs(diff);
index = vlc_dc_table[adiff];
if (component == 0) {
put_bits(&s->pb, vlc_dc_lum_bits[index], vlc_dc_lum_code[index]);
put_bits(
&s->pb,
mpeg1_lum_dc_uni[diff+255]&0xFF,
mpeg1_lum_dc_uni[diff+255]>>8);
} else {
put_bits(&s->pb, vlc_dc_chroma_bits[index], vlc_dc_chroma_code[index]);
}
if (diff > 0) {
put_bits(&s->pb, index, (diff & ((1 << index) - 1)));
} else if (diff < 0) {
put_bits(&s->pb, index, ((diff - 1) & ((1 << index) - 1)));
put_bits(
&s->pb,
mpeg1_chr_dc_uni[diff+255]&0xFF,
mpeg1_chr_dc_uni[diff+255]>>8);
}
}

4
libavcodec/mpeg12data.h
View File

@ -61,6 +61,10 @@ const unsigned char vlc_dc_chroma_bits[12] = {
2, 2, 2, 3, 4, 5, 6, 7, 8, 9, 10, 10,
};
/* simple include everything table for dc, first byte is bits number next 3 are code*/
static UINT32 mpeg1_lum_dc_uni[512];
static UINT32 mpeg1_chr_dc_uni[512];
static const UINT16 mpeg1_vlc[113][2] = {
{ 0x3, 2 }, { 0x4, 4 }, { 0x5, 5 }, { 0x6, 7 },
{ 0x26, 8 }, { 0x21, 8 }, { 0xa, 10 }, { 0x1d, 12 },