fix changing volume to 0% breaks channel ballance

[rui.chen@xxxxxxxxx (chen rui)]

Hi,

I fixed bug: #874 pulseaudio breaks per-channel volume config when
restoring volume from 0%.

I created arrayto record balance. When the volume change to 0%, I can
use last balance to calculate new volume.

Here is the patch:

Signed-off-by: Chen Rui <rui.chen at tieto.com>
---
  src/pulse/volume.c   |   23 +++++++++++++++++++++--
  src/pulsecore/sink.c |   21 ++++++++++++++++++++-
  2 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/src/pulse/volume.c b/src/pulse/volume.c
index f74d720..a51af0b 100644
--- a/src/pulse/volume.c
+++ b/src/pulse/volume.c
@@ -683,6 +683,8 @@ pa_cvolume* pa_cvolume_set_balance(pa_cvolume *v,
const pa_channel_map *map, flo

  pa_cvolume* pa_cvolume_scale(pa_cvolume *v, pa_volume_t max) {
      unsigned c;
+    static float balance[PA_CHANNELS_MAX/2] = {0};
+    pa_volume_t left, right;
      pa_volume_t t = 0;

      pa_assert(v);
@@ -692,8 +694,25 @@ pa_cvolume* pa_cvolume_scale(pa_cvolume *v,
pa_volume_t max) {

      t = pa_cvolume_max(v);

-    if (t <= PA_VOLUME_MUTED)
-        return pa_cvolume_set(v, v->channels, max);
+    for (c = 0; c < v->channels/2; c++){
+        left = v->values[2*c];
+        right = v->values[2*c+1];
+        if (left < right)
+            balance[c] = (1 - (float)left/right);
+        else if(left > right)
+            balance[c] = (-1 + (float)right/left);
+    }
+
+    if (t <= PA_VOLUME_MUTED){
+        pa_cvolume_set(v, v->channels, max);
+        for (c = 0; c < v->channels/2; c++){
+            if(balance[c] > 0)
+                v->values[2*c] = v->values[2*c] * (1 - balance[c]);
+            else if(balance[c] < 0)
+                v->values[2*c+1] = v->values[2*c+1] * (1 + balance[c]);
+        }
+        return v;
+    }

      for (c = 0; c < v->channels; c++)
          v->values[c] = (pa_volume_t) PA_CLAMP_VOLUME(((uint64_t)
v->values[c] * (uint64_t) max) / (uint64_t) t);
diff --git a/src/pulsecore/sink.c b/src/pulsecore/sink.c
index 7b4e626..e7076ad 100644
--- a/src/pulsecore/sink.c
+++ b/src/pulsecore/sink.c
@@ -1454,8 +1454,27 @@ void pa_sink_set_volume(

      if (volume) {

-        if (pa_cvolume_compatible(volume, &s->sample_spec))
+        if (pa_cvolume_compatible(volume, &s->sample_spec)){
+            pa_cvolume *tmp_volume = volume;
+            unsigned c;
+            static float balance[PA_CHANNELS_MAX/2];
+            for (c = 0; c < volume->channels/2; c++){
+                pa_volume_t left, right;
+                left = tmp_volume->values[2*c];
+                right = tmp_volume->values[2*c+1];
+                if (left < right)
+                    balance[c] = (1 - (float)left/right);
+                else if(left > right)
+                    balance[c] = (-1 + (float)right/left);
+                if(left == right && left == 0){
+                    if(balance[c] > 0)
+                        tmp_volume->values[2*c] =
tmp_volume->values[2*c] * (1 - balance[c]);
+                    else if(balance < 0)
+                        tmp_volume->values[2*c+1] =
tmp_volume->values[2*c+1] * (1 + balance[c]);
+                }
+            }
              s->reference_volume = *volume;
+        }
          else
              pa_cvolume_scale(&s->reference_volume,
pa_cvolume_max(volume));