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Simplify H.264 decode_cabac_mb_cbp_luma(), giving a ~0.5% speedup. 

patch by Andreas Öman, andreas olebyn nu
Date: Thu, 20 Sep 2007 12:59:19 +0200
Subject: [FFmpeg-devel] [PATCH] simplify h264's decode_cabac_mb_cbp_luma()

Originally committed as revision 10537 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Andreas Öman 2007-09-21 00:26:31 +00:00 committed by Diego Biurrun
parent dee15eceae
commit a27d6e714f
1 changed files with 11 additions and 56 deletions
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67
libavcodec/h264.c
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@ -4795,65 +4795,20 @@ static int decode_cabac_mb_chroma_pre_mode( H264Context *h) {
return 3; return 3;
} }
static const uint8_t block_idx_x[16] = {
0, 1, 0, 1, 2, 3, 2, 3, 0, 1, 0, 1, 2, 3, 2, 3
};
static const uint8_t block_idx_y[16] = {
0, 0, 1, 1, 0, 0, 1, 1, 2, 2, 3, 3, 2, 2, 3, 3
};
static const uint8_t block_idx_xy[4][4] = {
{ 0, 2, 8, 10},
{ 1, 3, 9, 11},
{ 4, 6, 12, 14},
{ 5, 7, 13, 15}
};
static int decode_cabac_mb_cbp_luma( H264Context *h) { static int decode_cabac_mb_cbp_luma( H264Context *h) {
int cbp = 0; int cbp_b, cbp_a, ctx, cbp = 0;
int cbp_b = -1;
int i8x8;
if( h->slice_table[h->top_mb_xy] == h->slice_num ) { cbp_a = h->slice_table[h->left_mb_xy[0]] == h->slice_num ? h->left_cbp : -1;
cbp_b = h->top_cbp; cbp_b = h->slice_table[h->top_mb_xy] == h->slice_num ? h->top_cbp : -1;
tprintf(h->s.avctx, "cbp_b = top_cbp = %x\n", cbp_b);
}
for( i8x8 = 0; i8x8 < 4; i8x8++ ) { ctx = !(cbp_a & 0x02) + 2 * !(cbp_b & 0x04);
int cbp_a = -1; cbp |= get_cabac_noinline(&h->cabac, &h->cabac_state[73 + ctx]);
int x, y; ctx = !(cbp & 0x01) + 2 * !(cbp_b & 0x08);
int ctx = 0; cbp |= get_cabac_noinline(&h->cabac, &h->cabac_state[73 + ctx]) << 1;
ctx = !(cbp_a & 0x08) + 2 * !(cbp & 0x01);
x = block_idx_x[4*i8x8]; cbp |= get_cabac_noinline(&h->cabac, &h->cabac_state[73 + ctx]) << 2;
y = block_idx_y[4*i8x8]; ctx = !(cbp & 0x04) + 2 * !(cbp & 0x02);
cbp |= get_cabac_noinline(&h->cabac, &h->cabac_state[73 + ctx]) << 3;
if( x > 0 )
cbp_a = cbp;
else if( h->slice_table[h->left_mb_xy[0]] == h->slice_num ) {
cbp_a = h->left_cbp;
tprintf(h->s.avctx, "cbp_a = left_cbp = %x\n", cbp_a);
}
if( y > 0 )
cbp_b = cbp;
/* No need to test for skip as we put 0 for skip block */
/* No need to test for IPCM as we put 1 for IPCM block */
if( cbp_a >= 0 ) {
int i8x8a = block_idx_xy[(x-1)&0x03][y]/4;
if( ((cbp_a >> i8x8a)&0x01) == 0 )
ctx++;
}
if( cbp_b >= 0 ) {
int i8x8b = block_idx_xy[x][(y-1)&0x03]/4;
if( ((cbp_b >> i8x8b)&0x01) == 0 )
ctx += 2;
}
if( get_cabac( &h->cabac, &h->cabac_state[73 + ctx] ) ) {
cbp |= 1 << i8x8;
}
}
return cbp; return cbp;
} }
static int decode_cabac_mb_cbp_chroma( H264Context *h) { static int decode_cabac_mb_cbp_chroma( H264Context *h) {