[FFmpeg-cvslog] r24468 - in trunk/libavcodec: vp56.h vp8.c vp8data.h
conrad
subversion
Fri Jul 23 23:46:17 CEST 2010
Author: conrad
Date: Fri Jul 23 23:46:17 2010
New Revision: 24468
Log:
Decode DCT tokens by branching to a different code path for each branch
on the huffman tree, instead of traversing the tree in a while loop.
Based on the similar optimization in libvpx's detokenize.c
10% faster at normal bitrates, and 30% faster for high-bitrate intra-only
Modified:
trunk/libavcodec/vp56.h
trunk/libavcodec/vp8.c
trunk/libavcodec/vp8data.h
Modified: trunk/libavcodec/vp56.h
==============================================================================
--- trunk/libavcodec/vp56.h Fri Jul 23 23:46:14 2010 (r24467)
+++ trunk/libavcodec/vp56.h Fri Jul 23 23:46:17 2010 (r24468)
@@ -226,6 +226,24 @@ static inline int vp56_rac_get_prob(VP56
return bit;
}
+// branchy variant, to be used where there's a branch based on the bit decoded
+static av_always_inline int vp56_rac_get_prob_branchy(VP56RangeCoder *c, int prob)
+{
+ unsigned long code_word = vp56_rac_renorm(c);
+ unsigned low = 1 + (((c->high - 1) * prob) >> 8);
+ unsigned low_shift = low << 8;
+
+ if (code_word >= low_shift) {
+ c->high -= low;
+ c->code_word = code_word - low_shift;
+ return 1;
+ }
+
+ c->high = low;
+ c->code_word = code_word;
+ return 0;
+}
+
static inline int vp56_rac_get(VP56RangeCoder *c)
{
unsigned int code_word = vp56_rac_renorm(c);
Modified: trunk/libavcodec/vp8.c
==============================================================================
--- trunk/libavcodec/vp8.c Fri Jul 23 23:46:14 2010 (r24467)
+++ trunk/libavcodec/vp8.c Fri Jul 23 23:46:17 2010 (r24468)
@@ -800,36 +800,61 @@ static int decode_block_coeffs(VP56Range
uint8_t probs[8][3][NUM_DCT_TOKENS-1],
int i, int zero_nhood, int16_t qmul[2])
{
- int token, nonzero = 0;
- int offset = 0;
+ uint8_t *token_prob;
+ int nonzero = 0;
+ int coeff;
- for (; i < 16; i++) {
- token = vp8_rac_get_tree_with_offset(c, vp8_coeff_tree, probs[vp8_coeff_band[i]][zero_nhood], offset);
+ do {
+ token_prob = probs[vp8_coeff_band[i]][zero_nhood];
- if (token == DCT_EOB)
- break;
- else if (token >= DCT_CAT1) {
- int cat = token-DCT_CAT1;
- token = vp8_rac_get_coeff(c, vp8_dct_cat_prob[cat]);
- token += 3 + (2<<cat);
- }
+ if (!vp56_rac_get_prob_branchy(c, token_prob[0])) // DCT_EOB
+ return nonzero;
- // after the first token, the non-zero prediction context becomes
- // based on the last decoded coeff
- if (!token) {
+skip_eob:
+ if (!vp56_rac_get_prob_branchy(c, token_prob[1])) { // DCT_0
zero_nhood = 0;
- offset = 1;
- continue;
- } else if (token == 1)
+ token_prob = probs[vp8_coeff_band[++i]][0];
+ if (i < 16)
+ goto skip_eob;
+ return nonzero; // invalid input; blocks should end with EOB
+ }
+
+ if (!vp56_rac_get_prob_branchy(c, token_prob[2])) { // DCT_1
+ coeff = 1;
zero_nhood = 1;
- else
+ } else {
zero_nhood = 2;
+ if (!vp56_rac_get_prob_branchy(c, token_prob[3])) { // DCT 2,3,4
+ coeff = vp56_rac_get_prob(c, token_prob[4]);
+ if (coeff)
+ coeff += vp56_rac_get_prob(c, token_prob[5]);
+ coeff += 2;
+ } else {
+ // DCT_CAT*
+ if (!vp56_rac_get_prob_branchy(c, token_prob[6])) {
+ if (!vp56_rac_get_prob_branchy(c, token_prob[7])) { // DCT_CAT1
+ coeff = 5 + vp56_rac_get_prob(c, vp8_dct_cat1_prob[0]);
+ } else { // DCT_CAT2
+ coeff = 7;
+ coeff += vp56_rac_get_prob(c, vp8_dct_cat2_prob[0]) << 1;
+ coeff += vp56_rac_get_prob(c, vp8_dct_cat2_prob[1]);
+ }
+ } else { // DCT_CAT3 and up
+ int a = vp56_rac_get_prob(c, token_prob[8]);
+ int b = vp56_rac_get_prob(c, token_prob[9+a]);
+ int cat = (a<<1) + b;
+ coeff = 3 + (8<<cat);
+ coeff += vp8_rac_get_coeff(c, vp8_dct_cat_prob[cat]);
+ }
+ }
+ }
+
// todo: full [16] qmat? load into register?
- block[zigzag_scan[i]] = (vp8_rac_get(c) ? -token : token) * qmul[!!i];
- nonzero = i+1;
- offset = 0;
- }
+ block[zigzag_scan[i]] = (vp8_rac_get(c) ? -coeff : coeff) * qmul[!!i];
+ nonzero = ++i;
+ } while (i < 16);
+
return nonzero;
}
Modified: trunk/libavcodec/vp8data.h
==============================================================================
--- trunk/libavcodec/vp8data.h Fri Jul 23 23:46:14 2010 (r24467)
+++ trunk/libavcodec/vp8data.h Fri Jul 23 23:46:17 2010 (r24468)
@@ -329,21 +329,6 @@ static const uint8_t vp8_coeff_band[16]
0, 1, 2, 3, 6, 4, 5, 6, 6, 6, 6, 6, 6, 6, 6, 7
};
-static const int8_t vp8_coeff_tree[NUM_DCT_TOKENS-1][2] =
-{
- { -DCT_EOB, 1 }, // '0'
- { -DCT_0, 2 }, // '10'
- { -DCT_1, 3 }, // '110'
- { 4, 6 },
- { -DCT_2, 5 }, // '11100'
- { -DCT_3, -DCT_4 }, // '111010', '111011'
- { 7, 8 },
- { -DCT_CAT1, -DCT_CAT2 }, // '111100', '111101'
- { 9, 10 },
- { -DCT_CAT3, -DCT_CAT4 }, // '1111100', '1111101'
- { -DCT_CAT5, -DCT_CAT6 }, // '1111110', '1111111'
-};
-
static const uint8_t vp8_dct_cat1_prob[] = { 159, 0 };
static const uint8_t vp8_dct_cat2_prob[] = { 165, 145, 0 };
static const uint8_t vp8_dct_cat3_prob[] = { 173, 148, 140, 0 };
@@ -351,10 +336,9 @@ static const uint8_t vp8_dct_cat4_prob[]
static const uint8_t vp8_dct_cat5_prob[] = { 180, 157, 141, 134, 130, 0 };
static const uint8_t vp8_dct_cat6_prob[] = { 254, 254, 243, 230, 196, 177, 153, 140, 133, 130, 129, 0 };
-static const uint8_t * const vp8_dct_cat_prob[6] =
+// only used for cat3 and above; cat 1 and 2 are referenced directly
+static const uint8_t * const vp8_dct_cat_prob[] =
{
- vp8_dct_cat1_prob,
- vp8_dct_cat2_prob,
vp8_dct_cat3_prob,
vp8_dct_cat4_prob,
vp8_dct_cat5_prob,
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