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mdct: work on 2 input buffers, and remove 1 encoding buffer

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Antoine SOULIER
2022-05-05 13:54:50 +02:00
parent 0cec73a6fb
commit 3568ee1cbf
8 changed files with 63 additions and 63 deletions
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47
src/mdct.c
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@@ -193,39 +193,35 @@ static struct lc3_complex *fft(const struct lc3_complex *x, int n,
/**
* Windowing of samples before MDCT
* dt, sr Duration and samplerate (size of the transform)
* x [-nd..-1] Previous, [0..ns-1] Current samples
* y Output `ns` windowed samples
*
* The number of previous samples `nd` accessed on `x` is :
* nd: `ns` * 23/30 for 7.5ms frame duration
* nd: `ns` * 5/ 8 for 10ms frame duration
* x, y Input current and delayed samples
* y, d Output windowed samples, and delayed ones
*/
static void mdct_window(
enum lc3_dt dt, enum lc3_srate sr, const float *x, float *y)
static void mdct_window(enum lc3_dt dt, enum lc3_srate sr,
const float *x, float *d, float *y)
{
int ns = LC3_NS(dt, sr), nd = LC3_ND(dt, sr);
const float *w0 = lc3_mdct_win[dt][sr], *w1 = w0 + ns;
const float *w2 = w1, *w3 = w2 + nd;
const float *x0 = x - nd, *x1 = x0 + ns;
const float *x2 = x1, *x3 = x2 + nd;
const float *x0 = x + ns-nd, *x1 = x0;
float *y0 = y + ns/2, *y1 = y0;
float *d0 = d, *d1 = d + nd;
while (x0 < x1) {
*(--y0) = *(x0++) * *(w0++) - *(--x1) * *(--w1);
*(--y0) = *(x0++) * *(w0++) - *(--x1) * *(--w1);
while (x1 > x) {
*(--y0) = *d0 * *(w0++) - *(--x1) * *(--w1);
*(y1++) = (*(d0++) = *(x0++)) * *(w2++);
*(--y0) = *d0 * *(w0++) - *(--x1) * *(--w1);
*(y1++) = (*(d0++) = *(x0++)) * *(w2++);
}
for (const float *xe = x2 + ns-nd; x2 < xe; ) {
*(y1++) = *(x2++) * *(w2++);
*(y1++) = *(x2++) * *(w2++);
}
for (x1 += ns; x0 < x1; ) {
*(--y0) = *d0 * *(w0++) - *(--d1) * *(--w1);
*(y1++) = (*(d0++) = *(x0++)) * *(w2++) + (*d1 = *(--x1)) * *(--w3);
while (x2 < x3) {
*(y1++) = *(x2++) * *(w2++) + *(--x3) * *(--w3);
*(y1++) = *(x2++) * *(w2++) + *(--x3) * *(--w3);
*(--y0) = *d0 * *(w0++) - *(--d1) * *(--w1);
*(y1++) = (*(d0++) = *(x0++)) * *(w2++) + (*d1 = *(--x1)) * *(--w3);
}
}
@@ -409,16 +405,17 @@ static void imdct_window(enum lc3_dt dt, enum lc3_srate sr,
* Forward MDCT transformation
*/
void lc3_mdct_forward(enum lc3_dt dt, enum lc3_srate sr,
enum lc3_srate sr_dst, const float *x, float *y)
enum lc3_srate sr_dst, const float *x, float *d, float *y)
{
const struct lc3_mdct_rot_def *rot = lc3_mdct_rot[dt][sr];
int nf = LC3_NS(dt, sr_dst);
int ns = LC3_NS(dt, sr);
union { float *f; struct lc3_complex *z; } u = { .f = y };
struct lc3_complex z[ns/2];
struct lc3_complex buffer[ns/2];
struct lc3_complex *z = (struct lc3_complex *)y;
union { float *f; struct lc3_complex *z; } u = { .z = buffer };
mdct_window(dt, sr, x, u.f);
mdct_window(dt, sr, x, d, u.f);
mdct_pre_fft(rot, u.f, u.z);
u.z = fft(u.z, ns/2, u.z, z);