[FFmpeg-cvslog] r26040 - trunk/libavcodec/ac3enc.c
jbr
subversion
Thu Dec 16 23:47:08 CET 2010
Author: jbr
Date: Thu Dec 16 23:47:07 2010
New Revision: 26040
Log:
Copy bap from previous block when exponent strategy is EXP_REUSE.
We can do this because exponents are the only bit allocation parameters which
change from block-to-block currently.
Approx. 57% faster in function bit_alloc().
Approx. 25% faster overall encoding.
Modified:
trunk/libavcodec/ac3enc.c
Modified: trunk/libavcodec/ac3enc.c
==============================================================================
--- trunk/libavcodec/ac3enc.c Thu Dec 16 23:47:04 2010 (r26039)
+++ trunk/libavcodec/ac3enc.c Thu Dec 16 23:47:07 2010 (r26040)
@@ -1028,10 +1028,18 @@ static int bit_alloc(AC3EncodeContext *s
mant_cnt[1] = mant_cnt[2] = 2;
mant_cnt[4] = 1;
for (ch = 0; ch < s->channels; ch++) {
+ /* Currently the only bit allocation parameters which vary across
+ blocks within a frame are the exponent values. We can take
+ advantage of that by reusing the bit allocation pointers
+ whenever we reuse exponents. */
+ if (block->exp_strategy[ch] == EXP_REUSE) {
+ memcpy(block->bap[ch], s->blocks[blk-1].bap[ch], AC3_MAX_COEFS);
+ } else {
ff_ac3_bit_alloc_calc_bap(block->mask[ch], block->psd[ch], 0,
s->nb_coefs[ch], snr_offset,
s->bit_alloc.floor, ff_ac3_bap_tab,
block->bap[ch]);
+ }
mantissa_bits += compute_mantissa_size(mant_cnt, block->bap[ch], s->nb_coefs[ch]);
}
mantissa_bits += compute_mantissa_size_final(mant_cnt);
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