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add api for manipulating volume balances

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This commit is contained in:
Lennart Poettering 2009-01-19 21:45:58 +01:00
parent 606cf8a2ec
commit 723d71a021
4 changed files with 136 additions and 0 deletions
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91
src/pulse/volume.c
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@ -402,3 +402,94 @@ int pa_cvolume_compatible(const pa_cvolume *v, const pa_sample_spec *ss) {
return v->channels == ss->channels;
}
static void get_avg_lr(const pa_channel_map *map, const pa_cvolume *v, pa_volume_t *l, pa_volume_t *r) {
int c;
pa_volume_t left = 0, right = 0;
unsigned n_left = 0, n_right = 0;
pa_assert(v);
pa_assert(map);
pa_assert(map->channels == v->channels);
pa_assert(l);
pa_assert(r);
for (c = 0; c < map->channels; c++) {
if (on_left(map->map[c])) {
left += v->values[c];
n_left++;
} else if (on_right(map->map[c])) {
right += v->values[c];
n_right++;
}
}
*l = left / n_left;
*r = right / n_right;
}
float pa_cvolume_get_balance(const pa_channel_map *map, const pa_cvolume *v) {
pa_volume_t left, right;
pa_assert(v);
pa_assert(map);
pa_assert(map->channels == v->channels);
get_avg_lr(map, v, &left, &right);
if (left == right)
return 0.0f;
/* 1.0, 0.0 => -1.0
0.0, 1.0 => 1.0
0.0, 0.0 => 0.0
0.5, 0.5 => 0.0
1.0, 0.5 => -0.5
1.0, 0.25 => -0.75
0.75, 0.25 => -0.66
0.5, 0.25 => -0.5 */
if (left > right)
return -1.0f + ((float) right / (float) left);
else
return 1.0f - ((float) left / (float) right);
}
pa_cvolume* pa_cvolume_set_balance(const pa_channel_map *map, pa_cvolume *v, float new_balance) {
pa_volume_t left, nleft, right, nright, m;
unsigned c;
pa_assert(map->channels == v->channels);
pa_assert(map);
pa_assert(v);
pa_assert(new_balance >= -1.0f);
pa_assert(new_balance <= 1.0f);
get_avg_lr(map, v, &left, &right);
m = PA_MAX(left, right);
if (new_balance <= 0) {
nright = (new_balance + 1.0f) * m;
nleft = m;
} else {
nleft = (1.0f - new_balance) * m;
nright = m;
}
for (c = 0; c < map->channels; c++) {
if (on_left(map->map[c])) {
if (left == 0)
v->values[c] = 0;
else
v->values[c] = (pa_volume_t) (((uint64_t) v->values[c] * (uint64_t) nleft) / (uint64_t) left);
} else if (on_right(map->map[c])) {
if (right == 0)
v->values[c] = 0;
else
v->values[c] = (pa_volume_t) (((uint64_t) v->values[c] * (uint64_t) nright) / (uint64_t) right);
}
}
return v;
}