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binkaudio: pre-calculate quantization factors

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This commit is contained in:
Justin Ruggles 2011-10-25 15:13:19 -04:00
parent 101ef19ef4
commit 9f48039a37
1 changed files with 7 additions and 2 deletions
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9
libavcodec/binkaudio.c
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@ -39,6 +39,8 @@
extern const uint16_t ff_wma_critical_freqs[25];
static float quant_table[95];
#define MAX_CHANNELS 2
#define BINK_BLOCK_MAX_SIZE (MAX_CHANNELS << 11)
@ -107,6 +109,10 @@ static av_cold int decode_init(AVCodecContext *avctx)
s->block_size = (s->frame_len - s->overlap_len) * s->channels;
sample_rate_half = (sample_rate + 1) / 2;
s->root = 2.0 / sqrt(s->frame_len);
for (i = 0; i < 95; i++) {
/* constant is result of 0.066399999/log10(M_E) */
quant_table[i] = expf(i * 0.15289164787221953823f) * s->root;
}
/* calculate number of bands */
for (s->num_bands = 1; s->num_bands < 25; s->num_bands++)
@ -190,9 +196,8 @@ static int decode_block(BinkAudioContext *s, short *out, int use_dct)
if (get_bits_left(gb) < s->num_bands * 8)
return AVERROR_INVALIDDATA;
for (i = 0; i < s->num_bands; i++) {
/* constant is result of 0.066399999/log10(M_E) */
int value = get_bits(gb, 8);
quant[i] = expf(FFMIN(value, 95) * 0.15289164787221953823f) * s->root;
quant[i] = quant_table[FFMIN(value, 95)];
}
k = 0;