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Process all EXP_REUSE blocks at once in exponent_min().

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43% faster in function encode_exponents().

Originally committed as revision 26358 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2011-01-15 01:59:21 +00:00
parent 7d87d56ff8
commit 964f2cf2a0
1 changed files with 25 additions and 12 deletions
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37
libavcodec/ac3enc.c
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@ -500,15 +500,25 @@ static void compute_exp_strategy(AC3EncodeContext *s)
/**
* Set each encoded exponent in a block to the minimum of itself and the
* exponent in the same frequency bin of a following block.
* exp[i] = min(exp[i], exp1[i]
* exponents in the same frequency bin of up to 5 following blocks.
*/
static void exponent_min(uint8_t *exp, uint8_t *exp1, int n)
static void exponent_min(uint8_t *exp, int num_reuse_blocks, int nb_coefs)
{
int i;
for (i = 0; i < n; i++) {
if (exp1[i] < exp[i])
exp[i] = exp1[i];
int blk, i;
if (!num_reuse_blocks)
return;
for (i = 0; i < nb_coefs; i++) {
uint8_t min_exp = *exp;
uint8_t *exp1 = exp + AC3_MAX_COEFS;
for (blk = 0; blk < num_reuse_blocks; blk++) {
uint8_t next_exp = *exp1;
if (next_exp < min_exp)
min_exp = next_exp;
exp1 += AC3_MAX_COEFS;
}
*exp++ = min_exp;
}
}
@ -589,7 +599,7 @@ static void encode_exponents(AC3EncodeContext *s)
{
int blk, blk1, ch;
uint8_t *exp, *exp1, *exp_strategy;
int nb_coefs;
int nb_coefs, num_reuse_blocks;
for (ch = 0; ch < s->channels; ch++) {
exp = s->blocks[0].exp[ch];
@ -599,13 +609,16 @@ static void encode_exponents(AC3EncodeContext *s)
blk = 0;
while (blk < AC3_MAX_BLOCKS) {
blk1 = blk + 1;
exp1 = exp + AC3_MAX_COEFS;
/* for the EXP_REUSE case we select the min of the exponents */
/* count the number of EXP_REUSE blocks after the current block */
while (blk1 < AC3_MAX_BLOCKS && exp_strategy[blk1] == EXP_REUSE) {
exponent_min(exp, exp1, nb_coefs);
blk1++;
exp1 += AC3_MAX_COEFS;
}
num_reuse_blocks = blk1 - blk - 1;
/* for the EXP_REUSE case we select the min of the exponents */
exponent_min(exp, num_reuse_blocks, nb_coefs);
encode_exponents_blk_ch(exp, nb_coefs,
exp_strategy[blk]);
/* copy encoded exponents for reuse case */