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Rewrite the SBR decoder QMF analysis filter on top of the IMDCT instead of the RDFT.

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This is based on a procedure to implement the filterbank on the DCT-IV described in
Hsu, H.W. et al. "A Complex Quadrature Mirror Filterbanks for MPEG-4 HE-AAC"
http://sites.google.com/site/wenchiehlee1020/Papers/ComplexFB_AES_121paper144.pdf

Originally committed as revision 23516 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Alex Converse
2010-06-07 21:52:08 +00:00
parent 082a0a33c4
commit 932963b8e2
2 changed files with 17 additions and 29 deletions
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44
libavcodec/aacsbr.c
View File

@@ -71,9 +71,6 @@ enum {
static VLC vlc_sbr[10];
static const int8_t vlc_sbr_lav[10] =
{ 60, 60, 24, 24, 31, 31, 12, 12, 31, 12 };
static DECLARE_ALIGNED(16, float, analysis_cos_pre)[64];
static DECLARE_ALIGNED(16, float, analysis_sin_pre)[64];
static DECLARE_ALIGNED(16, float, analysis_cossin_post)[32][2];
static const DECLARE_ALIGNED(16, float, zero64)[64];
#define SBR_INIT_VLC_STATIC(num, size) \
@@ -116,16 +113,6 @@ av_cold void ff_aac_sbr_init(void)
SBR_INIT_VLC_STATIC(8, 592);
SBR_INIT_VLC_STATIC(9, 512);
for (n = 0; n < 64; n++) {
float pre = M_PI * n / 64;
analysis_cos_pre[n] = cosf(pre);
analysis_sin_pre[n] = sinf(pre);
}
for (k = 0; k < 32; k++) {
float post = M_PI * (k + 0.5) / 128;
analysis_cossin_post[k][0] = 4.0 * cosf(post);
analysis_cossin_post[k][1] = -4.0 * sinf(post);
}
for (n = 1; n < 320; n++)
sbr_qmf_window_us[320 + n] = sbr_qmf_window_us[320 - n];
sbr_qmf_window_us[384] = -sbr_qmf_window_us[384];
@@ -142,13 +129,13 @@ av_cold void ff_aac_sbr_ctx_init(SpectralBandReplication *sbr)
sbr->data[0].synthesis_filterbank_samples_offset = SBR_SYNTHESIS_BUF_SIZE - (1280 - 128);
sbr->data[1].synthesis_filterbank_samples_offset = SBR_SYNTHESIS_BUF_SIZE - (1280 - 128);
ff_mdct_init(&sbr->mdct, 7, 1, 1.0/64);
ff_rdft_init(&sbr->rdft, 6, IDFT_R2C);
ff_mdct_init(&sbr->mdct_ana, 7, 1, -2.0);
}
av_cold void ff_aac_sbr_ctx_close(SpectralBandReplication *sbr)
{
ff_mdct_end(&sbr->mdct);
ff_rdft_end(&sbr->rdft);
ff_mdct_end(&sbr->mdct_ana);
}
static int qsort_comparison_function_int16(const void *a, const void *b)
@@ -1139,7 +1126,7 @@ static void sbr_dequant(SpectralBandReplication *sbr, int id_aac)
* @param x pointer to the beginning of the first sample window
* @param W array of complex-valued samples split into subbands
*/
static void sbr_qmf_analysis(DSPContext *dsp, RDFTContext *rdft, const float *in, float *x,
static void sbr_qmf_analysis(DSPContext *dsp, RDFTContext *mdct, const float *in, float *x,
float z[320], float W[2][32][32][2],
float scale)
{
@@ -1156,19 +1143,20 @@ static void sbr_qmf_analysis(DSPContext *dsp, RDFTContext *rdft, const float *in
dsp->vector_fmul_reverse(z, sbr_qmf_window_ds, x, 320);
for (k = 0; k < 64; k++) {
float f = z[k] + z[k + 64] + z[k + 128] + z[k + 192] + z[k + 256];
z[k] = f * analysis_cos_pre[k];
z[k+64] = f;
z[k] = f;
}
ff_rdft_calc(rdft, z);
re = z[0] * 0.5f;
im = 0.5f * dsp->scalarproduct_float(z+64, analysis_sin_pre, 64);
W[1][i][0][0] = re * analysis_cossin_post[0][0] - im * analysis_cossin_post[0][1];
W[1][i][0][1] = re * analysis_cossin_post[0][1] + im * analysis_cossin_post[0][0];
//Shuffle to IMDCT
z[64] = z[0];
for (k = 1; k < 32; k++) {
re = z[2*k ] - re;
im = z[2*k+1] - im;
W[1][i][k][0] = re * analysis_cossin_post[k][0] - im * analysis_cossin_post[k][1];
W[1][i][k][1] = re * analysis_cossin_post[k][1] + im * analysis_cossin_post[k][0];
z[64+2*k-1] = z[ k];
z[64+2*k ] = -z[64-k];
}
z[64+63] = z[32];
ff_imdct_half(mdct, z, z+64);
for (k = 0; k < 32; k++) {
W[1][i][k][0] = -z[63-k];
W[1][i][k][1] = z[k];
}
x += 32;
}
@@ -1730,7 +1718,7 @@ void ff_sbr_apply(AACContext *ac, SpectralBandReplication *sbr, int id_aac,
}
for (ch = 0; ch < nch; ch++) {
/* decode channel */
sbr_qmf_analysis(&ac->dsp, &sbr->rdft, ch ? R : L, sbr->data[ch].analysis_filterbank_samples,
sbr_qmf_analysis(&ac->dsp, &sbr->mdct_ana, ch ? R : L, sbr->data[ch].analysis_filterbank_samples,
(float*)sbr->qmf_filter_scratch,
sbr->data[ch].W, 1/(-1024 * ac->sf_scale));
sbr_lf_gen(ac, sbr, sbr->X_low, sbr->data[ch].W);

2
libavcodec/sbr.h
View File

@@ -176,7 +176,7 @@ typedef struct {
float s_m[7][48];
float gain[7][48];
DECLARE_ALIGNED(16, float, qmf_filter_scratch)[5][64];
RDFTContext rdft;
FFTContext mdct_ana;
FFTContext mdct;
} SpectralBandReplication;