[AFV] Ref T730, improved volume handling

* for the asymmetric output volume -60/18dB, make sure that normalized 50 means 0dB
* slider is centered
* return value if value for volume was changed

src/blackcore/afv/audio/input.cpp

@@ -94,6 +94,13 @@ namespace BlackCore
                 m_encoder.setBitRate(16 * 1024);
             }
 
+            bool CInput::setVolume(double volume)
+            {
+                if (qFuzzyCompare(m_volume, volume)) { return false; }
+                m_volume = volume;
+                return true;
+            }
+
             void CInput::start(const CAudioDeviceInfo &inputDevice)
             {
                 if (m_started) { return; }