source: rework volume handling

- drop the 'virtual_' prefix from s->virtual_volume since we don't
  distuingish between reference and real volumes for sources

- introduce an accuracy for source volumes: if the hardware can control
  the volume "close enough" don't necessarily adjust the rest in
  software unless it is beyond a certain threshold. This should save a
  little bit of CPU at the expensive of a bit of accuracy in volume
  handling.

- other minor cleanups

1 files changed, 24 insertions, 13 deletions

diff --git a/src/modules/alsa/alsa-source.c b/src/modules/alsa/alsa-source.c
index 9a51f857..7da37553 100644
--- a/src/modules/alsa/alsa-source.c
+++ b/src/modules/alsa/alsa-source.c
@@ -65,6 +65,8 @@
 #define TSCHED_MIN_SLEEP_USEC (10*PA_USEC_PER_MSEC)          /* 10ms */
 #define TSCHED_MIN_WAKEUP_USEC (4*PA_USEC_PER_MSEC)          /* 4ms */
 
+#define VOLUME_ACCURACY (PA_VOLUME_NORM/100)
+
 struct userdata {
     pa_core *core;
     pa_module *module;
@@ -987,15 +989,11 @@ static void source_get_volume_cb(pa_source *s) {
     if (pa_cvolume_equal(&u->hardware_volume, &r))
         return;
 
-    s->virtual_volume = u->hardware_volume = r;
-
-    if (u->mixer_path->has_dB) {
-        pa_cvolume reset;
+    s->volume = u->hardware_volume = r;
 
-        /* Hmm, so the hardware volume changed, let's reset our software volume */
-        pa_cvolume_reset(&reset, s->sample_spec.channels);
-        pa_source_set_soft_volume(s, &reset);
-    }
+    /* Hmm, so the hardware volume changed, let's reset our software volume */
+    if (u->mixer_path->has_dB)
+        pa_source_set_soft_volume(s, NULL);
 }
 
 static void source_set_volume_cb(pa_source *s) {
@@ -1008,7 +1006,7 @@ static void source_set_volume_cb(pa_source *s) {
     pa_assert(u->mixer_handle);
 
     /* Shift up by the base volume */
-    pa_sw_cvolume_divide_scalar(&r, &s->virtual_volume, s->base_volume);
+    pa_sw_cvolume_divide_scalar(&r, &s->volume, s->base_volume);
 
     if (pa_alsa_path_set_volume(u->mixer_path, u->mixer_handle, &s->channel_map, &r) < 0)
         return;
@@ -1019,13 +1017,26 @@ static void source_set_volume_cb(pa_source *s) {
     u->hardware_volume = r;
 
     if (u->mixer_path->has_dB) {
+        pa_cvolume new_soft_volume;
+        pa_bool_t accurate_enough;
 
         /* Match exactly what the user requested by software */
-        pa_sw_cvolume_divide(&s->soft_volume, &s->virtual_volume, &u->hardware_volume);
+        pa_sw_cvolume_divide(&new_soft_volume, &s->volume, &u->hardware_volume);
+
+        /* If the adjustment to do in software is only minimal we
+         * can skip it. That saves us CPU at the expense of a bit of
+         * accuracy */
+        accurate_enough =
+            (pa_cvolume_min(&new_soft_volume) >= (PA_VOLUME_NORM - VOLUME_ACCURACY)) &&
+            (pa_cvolume_max(&new_soft_volume) <= (PA_VOLUME_NORM + VOLUME_ACCURACY));
 
-        pa_log_debug("Requested volume: %s", pa_cvolume_snprint(t, sizeof(t), &s->virtual_volume));
+        pa_log_debug("Requested volume: %s", pa_cvolume_snprint(t, sizeof(t), &s->volume));
         pa_log_debug("Got hardware volume: %s", pa_cvolume_snprint(t, sizeof(t), &u->hardware_volume));
-        pa_log_debug("Calculated software volume: %s", pa_cvolume_snprint(t, sizeof(t), &s->soft_volume));
+        pa_log_debug("Calculated software volume: %s (accurate-enough=%s)", pa_cvolume_snprint(t, sizeof(t), &new_soft_volume),
+                     pa_yes_no(accurate_enough));
+
+        if (!accurate_enough)
+            s->soft_volume = new_soft_volume;
 
     } else {
         pa_log_debug("Wrote hardware volume: %s", pa_cvolume_snprint(t, sizeof(t), &r));
@@ -1033,7 +1044,7 @@ static void source_set_volume_cb(pa_source *s) {
         /* We can't match exactly what the user requested, hence let's
          * at least tell the user about it */
 
-        s->virtual_volume = r;
+        s->volume = r;
     }
 }