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only calculate number of exponent groups when exponents are not reused.

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Originally committed as revision 13587 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles 2008-05-31 21:53:31 +00:00
parent aa148649a4
commit b85a15fe73
1 changed files with 11 additions and 9 deletions
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20
libavcodec/ac3dec.c
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@ -154,6 +154,7 @@ typedef struct {
int end_freq[AC3_MAX_CHANNELS]; ///< end frequency bin
AC3BitAllocParameters bit_alloc_params; ///< bit allocation parameters
int num_exp_groups[AC3_MAX_CHANNELS]; ///< Number of exponent groups
int8_t dexps[AC3_MAX_CHANNELS][256]; ///< decoded exponents
uint8_t bap[AC3_MAX_CHANNELS][256]; ///< bit allocation pointers
int16_t psd[AC3_MAX_CHANNELS][256]; ///< scaled exponents
@ -907,6 +908,7 @@ static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
for (ch = 1; ch <= fbw_channels; ch++) {
s->start_freq[ch] = 0;
if (s->exp_strategy[ch] != EXP_REUSE) {
int group_size;
int prev = s->end_freq[ch];
if (s->channel_in_cpl[ch])
s->end_freq[ch] = s->start_freq[CPL_CH];
@ -918,26 +920,26 @@ static int ac3_parse_audio_block(AC3DecodeContext *s, int blk)
}
s->end_freq[ch] = bandwidth_code * 3 + 73;
}
group_size = 3 << (s->exp_strategy[ch] - 1);
s->num_exp_groups[ch] = (s->end_freq[ch]+group_size-4) / group_size;
if(blk > 0 && s->end_freq[ch] != prev)
memset(bit_alloc_stages, 3, AC3_MAX_CHANNELS);
}
}
s->start_freq[s->lfe_ch] = 0;
s->end_freq[s->lfe_ch] = 7;
s->num_exp_groups[s->lfe_ch] = 2;
if (s->cpl_in_use && s->exp_strategy[CPL_CH] != EXP_REUSE) {
s->num_exp_groups[CPL_CH] = (s->end_freq[CPL_CH] - s->start_freq[CPL_CH]) /
(3 << (s->exp_strategy[CPL_CH] - 1));
}
/* decode exponents for each channel */
for (ch = !s->cpl_in_use; ch <= s->channels; ch++) {
if (s->exp_strategy[ch] != EXP_REUSE) {
int group_size, num_groups;
group_size = 3 << (s->exp_strategy[ch] - 1);
if(ch == CPL_CH)
num_groups = (s->end_freq[ch] - s->start_freq[ch]) / group_size;
else if(ch == s->lfe_ch)
num_groups = 2;
else
num_groups = (s->end_freq[ch] + group_size - 4) / group_size;
s->dexps[ch][0] = get_bits(gbc, 4) << !ch;
decode_exponents(gbc, s->exp_strategy[ch], num_groups, s->dexps[ch][0],
decode_exponents(gbc, s->exp_strategy[ch],
s->num_exp_groups[ch], s->dexps[ch][0],
&s->dexps[ch][s->start_freq[ch]+!!ch]);
if(ch != CPL_CH && ch != s->lfe_ch)
skip_bits(gbc, 2); /* skip gainrng */