[FFmpeg-cvslog] r15101 - trunk/libavcodec/eac3dec.c
jbr
subversion
Sun Aug 31 05:01:56 CEST 2008
Author: jbr
Date: Sun Aug 31 05:01:56 2008
New Revision: 15101
Log:
simplify code and comment regarding determination whether or not AHT is used.
Modified:
trunk/libavcodec/eac3dec.c
Modified: trunk/libavcodec/eac3dec.c
==============================================================================
--- trunk/libavcodec/eac3dec.c (original)
+++ trunk/libavcodec/eac3dec.c Sun Aug 31 05:01:56 2008
@@ -420,21 +420,21 @@ int ff_eac3_parse_header(AC3DecodeContex
/* determine which channels use AHT */
if (parse_aht_info) {
- /* AHT is only available when there are 6 blocks in the frame.
- The coupling channel can only use AHT when coupling is in use for
- all blocks.
- reference: Section E3.3.2 Bit Stream Helper Variables */
+ /* For AHT to be used, all non-zero blocks must reuse exponents from
+ the first block. Furthermore, for AHT to be used in the coupling
+ channel, all blocks must use coupling and use the same coupling
+ strategy. */
s->channel_uses_aht[CPL_CH]=0;
for (ch = (num_cpl_blocks != 6); ch <= s->channels; ch++) {
- int nchregs = 0;
- for (blk = 0; blk < 6; blk++) {
- if (ch)
- nchregs += (s->exp_strategy[blk][ch] != EXP_REUSE);
- else
- nchregs += s->cpl_strategy_exists[blk] ||
- (s->exp_strategy[blk][CPL_CH] != EXP_REUSE);
+ int use_aht = 1;
+ for (blk = 1; blk < 6; blk++) {
+ if ((s->exp_strategy[blk][ch] != EXP_REUSE) ||
+ (!ch && s->cpl_strategy_exists[blk])) {
+ use_aht = 0;
+ break;
+ }
}
- s->channel_uses_aht[ch] = (nchregs == 1) && get_bits1(gbc);
+ s->channel_uses_aht[ch] = use_aht && get_bits1(gbc);
}
} else {
memset(s->channel_uses_aht, 0, sizeof(s->channel_uses_aht));
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