From: Stefan Huber <shuber@xxxxxxxx>
Remixing one channel map to another is (except for special cases) done
via a linear mapping between channels, whose corresponding matrix is
computed by calc_map_table(). The k-th row in this matrix corresponds to
the coefficients of the linear combination of the input channels that
result in the k-th output channel. In order to avoid clipping of samples
we require that the sum of these coefficients is (at most) 1. This
commit ensures this.
Prior to this commit tests/remix-test.c gives 52 of 132 matrices that
violate this property. For example:
'front-left,front-right,front-center,lfe' -> 'front-left,front-right'
prior this commit after this commit
I00 I01 I02 I03 I00 I01 I02 I03
+------------------------ +------------------------
O00 | 0.750 0.000 0.375 0.375 O00 | 0.533 0.000 0.267 0.200
O01 | 0.000 0.750 0.375 0.375 O01 | 0.000 0.533 0.267 0.200
Building the matrix is done in several steps. However, only insufficient
measures are taken in order to preserve a row-sum of 1.0 (or leaves it
at 0.0) after each step. The current patch adds a post-processing step
in order check for each row whether the sum exceeds 1.0 and, if
necessary, normalizes this row. This allows for further simplifactions:
- The insufficient normalizations after some steps are removed. Gains
are adapted to (partially) resemble the old matrices.
- Handling unconnected input channls becomes a lot simpler.
---
src/pulsecore/resampler.c | 182 +++++++++++++++------------------------------
1 file changed, 62 insertions(+), 120 deletions(-)
diff --git a/src/pulsecore/resampler.c b/src/pulsecore/resampler.c
index 88e74e0..449d5fd 100644
--- a/src/pulsecore/resampler.c
+++ b/src/pulsecore/resampler.c
@@ -727,16 +727,17 @@ static void calc_map_table(pa_resampler *r) {
*
* 6) Make sure S:Left/S:Right is used: S:Left/S:Right: If not
* connected, mix into all D:left and all D:right channels. Gain is
- * 0.1, the current left and right should be multiplied by 0.9.
+ * 1/9.
*
* 7) Make sure S:Center, S:LFE is used:
*
* S:Center, S:LFE: If not connected, mix into all D:left, all
- * D:right, all D:center channels, gain is 0.375. The current (as
- * result of 1..6) factors should be multiplied by 0.75. (Alt.
- * suggestion: 0.25 vs. 0.5) If C-front is only mixed into
- * L-front/R-front if available, otherwise into all L/R channels.
- * Similarly for C-rear.
+ * D:right, all D:center channels. Gain is 0.5 for center and 0.375
+ * for LFE. C-front is only mixed into L-front/R-front if available,
+ * otherwise into all L/R channels. Similarly for C-rear.
+ *
+ * 8) Normalize each row in the matrix such that the sum for each row is
+ * not larger than 1.0 in order to avoid clipping.
*
* S: and D: shall relate to the source resp. destination channels.
*
@@ -759,6 +760,7 @@ static void calc_map_table(pa_resampler *r) {
ic_unconnected_right = 0,
ic_unconnected_center = 0,
ic_unconnected_lfe = 0;
+ unsigned ic_center_mixedin = 0;
pa_assert(remix);
@@ -885,159 +887,99 @@ static void calc_map_table(pa_resampler *r) {
ic_unconnected_lfe++;
}
- if (ic_unconnected_left > 0) {
+ for (ic = 0; ic < n_ic; ic++) {
+ pa_channel_position_t a = r->i_cm.map[ic];
- /* OK, so there are unconnected input channels on the left. Let's
- * multiply all already connected channels on the left side by .9
- * and add in our averaged unconnected channels multiplied by .1 */
+ if (ic_connected[ic])
+ continue;
for (oc = 0; oc < n_oc; oc++) {
+ pa_channel_position_t b = r->o_cm.map[oc];
- if (!on_left(r->o_cm.map[oc]))
- continue;
-
- for (ic = 0; ic < n_ic; ic++) {
+ if (on_left(a) && on_left(b))
+ m->map_table_f[oc][ic] = (1.f/9.f) / (float) ic_unconnected_left;
- if (ic_connected[ic]) {
- m->map_table_f[oc][ic] *= .9f;
- continue;
- }
+ else if (on_right(a) && on_right(b))
+ m->map_table_f[oc][ic] = (1.f/9.f) / (float) ic_unconnected_right;
- if (on_left(r->i_cm.map[ic]))
- m->map_table_f[oc][ic] = .1f / (float) ic_unconnected_left;
+ else if (on_center(a) && on_center(b)) {
+ m->map_table_f[oc][ic] = (1.f/9.f) / (float) ic_unconnected_center;
+ ic_center_mixedin = true;
}
+
+ else if (on_lfe(a) && !(r->flags & PA_RESAMPLER_NO_LFE))
+ m->map_table_f[oc][ic] = .375f / (float) ic_unconnected_lfe;
}
}
- if (ic_unconnected_right > 0) {
+ if (ic_unconnected_center > 0 && !ic_center_mixedin) {
+ unsigned ncenter[PA_CHANNELS_MAX];
+ bool found_frs[PA_CHANNELS_MAX];
- /* OK, so there are unconnected input channels on the right. Let's
- * multiply all already connected channels on the right side by .9
- * and add in our averaged unconnected channels multiplied by .1 */
+ memset(ncenter, 0, sizeof(ncenter));
+ memset(found_frs, 0, sizeof(found_frs));
- for (oc = 0; oc < n_oc; oc++) {
+ /* Hmm, as it appears there was no center channel we
+ could mix our center channel in. In this case, mix it into
+ left and right. Using .5 and 0.75 as factors. */
+
+ for (ic = 0; ic < n_ic; ic++) {
- if (!on_right(r->o_cm.map[oc]))
+ if (ic_connected[ic])
continue;
- for (ic = 0; ic < n_ic; ic++) {
+ if (!on_center(r->i_cm.map[ic]))
+ continue;
+
+ for (oc = 0; oc < n_oc; oc++) {
- if (ic_connected[ic]) {
- m->map_table_f[oc][ic] *= .9f;
+ if (!on_left(r->o_cm.map[oc]) && !on_right(r->o_cm.map[oc]))
continue;
- }
- if (on_right(r->i_cm.map[ic]))
- m->map_table_f[oc][ic] = .1f / (float) ic_unconnected_right;
+ if (front_rear_side(r->i_cm.map[ic]) == front_rear_side(r->o_cm.map[oc])) {
+ found_frs[ic] = true;
+ break;
+ }
}
- }
- }
-
- if (ic_unconnected_center > 0) {
- bool mixed_in = false;
-
- /* OK, so there are unconnected input channels on the center. Let's
- * multiply all already connected channels on the center side by .9
- * and add in our averaged unconnected channels multiplied by .1 */
-
- for (oc = 0; oc < n_oc; oc++) {
- if (!on_center(r->o_cm.map[oc]))
- continue;
-
- for (ic = 0; ic < n_ic; ic++) {
+ for (oc = 0; oc < n_oc; oc++) {
- if (ic_connected[ic]) {
- m->map_table_f[oc][ic] *= .9f;
+ if (!on_left(r->o_cm.map[oc]) && !on_right(r->o_cm.map[oc]))
continue;
- }
- if (on_center(r->i_cm.map[ic])) {
- m->map_table_f[oc][ic] = .1f / (float) ic_unconnected_center;
- mixed_in = true;
- }
+ if (!found_frs[ic] || front_rear_side(r->i_cm.map[ic]) == front_rear_side(r->o_cm.map[oc]))
+ ncenter[oc]++;
}
}
- if (!mixed_in) {
- unsigned ncenter[PA_CHANNELS_MAX];
- bool found_frs[PA_CHANNELS_MAX];
+ for (oc = 0; oc < n_oc; oc++) {
- memset(ncenter, 0, sizeof(ncenter));
- memset(found_frs, 0, sizeof(found_frs));
+ if (!on_left(r->o_cm.map[oc]) && !on_right(r->o_cm.map[oc]))
+ continue;
- /* Hmm, as it appears there was no center channel we
- could mix our center channel in. In this case, mix it into
- left and right. Using .375 and 0.75 as factors. */
+ if (ncenter[oc] <= 0)
+ continue;
for (ic = 0; ic < n_ic; ic++) {
- if (ic_connected[ic])
- continue;
-
if (!on_center(r->i_cm.map[ic]))
continue;
- for (oc = 0; oc < n_oc; oc++) {
-
- if (!on_left(r->o_cm.map[oc]) && !on_right(r->o_cm.map[oc]))
- continue;
-
- if (front_rear_side(r->i_cm.map[ic]) == front_rear_side(r->o_cm.map[oc])) {
- found_frs[ic] = true;
- break;
- }
- }
-
- for (oc = 0; oc < n_oc; oc++) {
-
- if (!on_left(r->o_cm.map[oc]) && !on_right(r->o_cm.map[oc]))
- continue;
-
- if (!found_frs[ic] || front_rear_side(r->i_cm.map[ic]) == front_rear_side(r->o_cm.map[oc]))
- ncenter[oc]++;
- }
- }
-
- for (oc = 0; oc < n_oc; oc++) {
-
- if (!on_left(r->o_cm.map[oc]) && !on_right(r->o_cm.map[oc]))
- continue;
-
- if (ncenter[oc] <= 0)
- continue;
-
- for (ic = 0; ic < n_ic; ic++) {
-
- if (ic_connected[ic]) {
- m->map_table_f[oc][ic] *= .75f;
- continue;
- }
-
- if (!on_center(r->i_cm.map[ic]))
- continue;
-
- if (!found_frs[ic] || front_rear_side(r->i_cm.map[ic]) == front_rear_side(r->o_cm.map[oc]))
- m->map_table_f[oc][ic] = .375f / (float) ncenter[oc];
- }
+ if (!found_frs[ic] || front_rear_side(r->i_cm.map[ic]) == front_rear_side(r->o_cm.map[oc]))
+ m->map_table_f[oc][ic] = .5f / (float) ncenter[oc];
}
}
}
+ }
- if (ic_unconnected_lfe > 0 && !(r->flags & PA_RESAMPLER_NO_LFE)) {
-
- /* OK, so there is an unconnected LFE channel. Let's mix it into
- * all channels, with factor 0.375 */
-
- for (ic = 0; ic < n_ic; ic++) {
-
- if (!on_lfe(r->i_cm.map[ic]))
- continue;
+ for (oc = 0; oc < n_oc; oc++) {
+ float sum = 0.0f;
+ for (ic = 0; ic < n_ic; ic++)
+ sum += m->map_table_f[oc][ic];
- for (oc = 0; oc < n_oc; oc++)
- m->map_table_f[oc][ic] = 0.375f / (float) ic_unconnected_lfe;
- }
- }
+ if (sum > 1.0f)
+ for (ic = 0; ic < n_ic; ic++)
+ m->map_table_f[oc][ic] /= sum;
}
/* make an 16:16 int version of the matrix */
--
1.7.9.5
