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avfilter/af_surround: improve front center channel

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Stops producing too loud output of front center channel in stereo upmix
by using average magnitude instead of square root of squared magnitudes.
This commit is contained in:
Paul B Mahol 2022-11-18 13:18:57 +01:00
parent 12b4ab5d4d
commit 08b4c3d6d6
1 changed files with 9 additions and 2 deletions
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11
libavfilter/af_surround.c
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@ -108,6 +108,7 @@ typedef struct AudioSurroundContext {
float *l_phase;
float *r_phase;
float *c_phase;
float *c_mag;
float *lfe_mag;
float *mag_total;
@ -304,11 +305,12 @@ static int config_output(AVFilterLink *outlink)
s->y_pos = av_calloc(s->rdft_size, sizeof(*s->y_pos));
s->l_phase = av_calloc(s->rdft_size, sizeof(*s->l_phase));
s->r_phase = av_calloc(s->rdft_size, sizeof(*s->r_phase));
s->c_mag = av_calloc(s->rdft_size, sizeof(*s->c_mag));
s->c_phase = av_calloc(s->rdft_size, sizeof(*s->c_phase));
s->mag_total = av_calloc(s->rdft_size, sizeof(*s->mag_total));
s->lfe_mag = av_calloc(s->rdft_size, sizeof(*s->lfe_mag));
if (!s->x_pos || !s->y_pos || !s->l_phase || !s->r_phase ||
!s->c_phase || !s->mag_total || !s->lfe_mag)
!s->c_phase || !s->mag_total || !s->lfe_mag || !s->c_mag)
return AVERROR(ENOMEM);
return 0;
@ -401,6 +403,7 @@ static int stereo_upmix(AVFilterContext *ctx, int ch)
const float *l_phase = s->l_phase;
const float *r_phase = s->r_phase;
const float *lfe_mag = s->lfe_mag;
const float *c_mag = s->c_mag;
const float *x = s->x_pos;
const float *y = s->y_pos;
const int chan = av_channel_layout_channel_from_index(&s->out_ch_layout, ch);
@ -410,7 +413,7 @@ static int stereo_upmix(AVFilterContext *ctx, int ch)
switch (chan) {
case AV_CHAN_FRONT_CENTER:
for (int n = 0; n < rdft_size; n++) {
float mag = powf(1.f - fabsf(x[n]), f_x) * powf((y[n] + 1.f) * .5f, f_y) * mag_total[n];
float mag = powf(1.f - fabsf(x[n]), f_x) * powf((y[n] + 1.f) * .5f, f_y) * c_mag[n];
float ph = c_phase[n];
TRANSFORM
@ -746,6 +749,7 @@ static void filter_stereo(AVFilterContext *ctx)
float *lphase = s->l_phase;
float *rphase = s->r_phase;
float *cphase = s->c_phase;
float *cmag = s->c_mag;
float *xpos = s->x_pos;
float *ypos = s->y_pos;
@ -760,6 +764,7 @@ static void filter_stereo(AVFilterContext *ctx)
float r_phase = atan2f(r_im, r_re);
float phase_dif = fabsf(l_phase - r_phase);
float mag_sum = l_mag + r_mag;
float c_mag = mag_sum * 0.5f;
float mag_dif, x, y;
mag_sum = mag_sum < MIN_MAG_SUM ? 1.f : mag_sum;
@ -776,6 +781,7 @@ static void filter_stereo(AVFilterContext *ctx)
ypos[n] = y;
lphase[n] = l_phase;
rphase[n] = r_phase;
cmag[n] = c_mag;
cphase[n] = c_phase;
magtotal[n] = mag_total;
}
@ -1344,6 +1350,7 @@ static av_cold void uninit(AVFilterContext *ctx)
av_freep(&s->y_pos);
av_freep(&s->l_phase);
av_freep(&s->r_phase);
av_freep(&s->c_mag);
av_freep(&s->c_phase);
av_freep(&s->mag_total);
av_freep(&s->lfe_mag);