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AAC: Use a sign LUT rather than 1-2*get_bits1()

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Patch by Alex Converse (alex converse gmail com)

Originally committed as revision 16041 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Alex Converse 2008-12-09 17:14:42 +00:00 committed by Robert Swain
parent c0893c3abb
commit 4a904903dc
1 changed files with 5 additions and 4 deletions
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9
libavcodec/aac.c
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@ -741,6 +741,7 @@ static int decode_spectrum_and_dequant(AACContext * ac, float coef[1024], GetBit
const int c = 1024/ics->num_windows;
const uint16_t * offsets = ics->swb_offset;
float *coef_base = coef;
static const float sign_lookup[] = { 1.0f, -1.0f };
for (g = 0; g < ics->num_windows; g++)
memset(coef + g * 128 + offsets[ics->max_sfb], 0, sizeof(float)*(c - offsets[ics->max_sfb]));
@ -784,11 +785,11 @@ static int decode_spectrum_and_dequant(AACContext * ac, float coef[1024], GetBit
}
vq_ptr = &ff_aac_codebook_vectors[cur_band_type - 1][index * dim];
if (is_cb_unsigned) {
if (vq_ptr[0]) coef[coef_tmp_idx ] = 1 - 2*(int)get_bits1(gb);
if (vq_ptr[1]) coef[coef_tmp_idx + 1] = 1 - 2*(int)get_bits1(gb);
if (vq_ptr[0]) coef[coef_tmp_idx ] = sign_lookup[get_bits1(gb)];
if (vq_ptr[1]) coef[coef_tmp_idx + 1] = sign_lookup[get_bits1(gb)];
if (dim == 4) {
if (vq_ptr[2]) coef[coef_tmp_idx + 2] = 1 - 2*(int)get_bits1(gb);
if (vq_ptr[3]) coef[coef_tmp_idx + 3] = 1 - 2*(int)get_bits1(gb);
if (vq_ptr[2]) coef[coef_tmp_idx + 2] = sign_lookup[get_bits1(gb)];
if (vq_ptr[3]) coef[coef_tmp_idx + 3] = sign_lookup[get_bits1(gb)];
}
}else {
coef[coef_tmp_idx ] = 1.0f;