Auto-adjustment of channel faders

ChangeLog

@@ -1,7 +1,8 @@
 
 ### 3.7.0dev <- NOTE: the release version number will be 3.7.1 ###
 
-
+- Automatic channel fader adjustment simplifies mixer setup by using the channel level meters (#1071).
+  (contributed by @JohannesBrx)
 
 ### 3.7.0 (2021-03-17) ###
 

src/audiomixerboard.cpp

@@ -857,6 +857,8 @@ CAudioMixerBoard::CAudioMixerBoard ( QWidget* parent ) :
     // create all mixer controls and make them invisible
     vecpChanFader.Init ( MAX_NUM_CHANNELS );
 
+    vecAvgLevels.Init ( MAX_NUM_CHANNELS, 0.0f );
+
     for ( int i = 0; i < MAX_NUM_CHANNELS; i++ )
     {
         vecpChanFader[i] = new CChannelFader ( this );
@@ -1145,6 +1147,7 @@ void CAudioMixerBoard::ApplyNewConClientList ( CVector<CChannelInfo>& vecChanInf
                     {
                         // the fader was not in use, reset everything for new client
                         vecpChanFader[i]->Reset();
+                        vecAvgLevels[i] = 0.0f;
 
                         // check if this is my own fader and set fader property
                         if ( i == iMyChannelID )
@@ -1308,6 +1311,169 @@ void CAudioMixerBoard::SetAllFaderLevelsToNewClientLevel()
     }
 }
 
+void CAudioMixerBoard::AutoAdjustAllFaderLevels()
+{
+    QMutexLocker locker ( &Mutex );
+
+    // initialize variables used for statistics
+    float vecMaxLevel[MAX_NUM_FADER_GROUPS + 1];
+    int   vecChannelsPerGroup[MAX_NUM_FADER_GROUPS + 1];
+    for ( int i = 0; i < MAX_NUM_FADER_GROUPS + 1; ++i )
+    {
+        vecMaxLevel[i] = LOW_BOUND_SIG_METER;
+        vecChannelsPerGroup[i] = 0;
+    }
+    CVector<CVector<float>> levels;
+    levels.resize ( MAX_NUM_FADER_GROUPS + 1 );
+
+    // compute min/max level per group and number of channels per group
+    for ( int i = 0; i < MAX_NUM_CHANNELS; ++i )
+    {
+        // only apply to visible faders (and not to my own channel fader)
+        if ( vecpChanFader[i]->IsVisible() && ( i != iMyChannelID ) )
+        {
+            // map averaged meter output level to decibels
+            // (invert CStereoSignalLevelMeter::CalcLogResultForMeter)
+            float leveldB = vecAvgLevels[i] *
+                ( UPPER_BOUND_SIG_METER - LOW_BOUND_SIG_METER ) /
+                NUM_STEPS_LED_BAR + LOW_BOUND_SIG_METER;
+
+            int group = vecpChanFader[i]->GetGroupID();
+            if ( group == INVALID_INDEX )
+            {
+                group = MAX_NUM_FADER_GROUPS;
+            }
+
+            if ( leveldB >= AUTO_FADER_NOISE_THRESHOLD_DB )
+            {
+                vecMaxLevel[group] = fmax ( vecMaxLevel[group], leveldB );
+                levels[group].Add ( leveldB );
+            }
+            ++vecChannelsPerGroup[group];
+        }
+    }
+
+    // sort levels for later median computation
+    for ( int i = 0; i < MAX_NUM_FADER_GROUPS + 1; ++i )
+    {
+        std::sort ( levels[i].begin(), levels[i].end() );
+    }
+
+    // compute the number of active groups (at least one channel)
+    int cntActiveGroups = 0;
+    for ( int i = 0; i < MAX_NUM_FADER_GROUPS; ++i )
+    {
+        cntActiveGroups += vecChannelsPerGroup[i] > 0;
+    }
+
+    // only my channel is active, nothing to do
+    if ( cntActiveGroups == 0 &&
+        vecChannelsPerGroup[MAX_NUM_FADER_GROUPS] == 0 )
+    {
+        return;
+    }
+
+    // compute target level for each group
+    // (prevent clipping when each group contributes at maximum level)
+    float targetLevelPerGroup = -20.0f * log10 (
+        std::max ( cntActiveGroups, 1 ) );
+
+    // compute target levels for the channels of each group individually
+    float vecTargetChannelLevel[MAX_NUM_FADER_GROUPS + 1];
+    float levelOffset = 0.0f;
+    float minFader = 0.0f;
+    for ( int i = 0; i < MAX_NUM_FADER_GROUPS + 1; ++i )
+    {
+        // compute the target level for each channel in the current group
+        // (prevent clipping when each channel in this group contributes at
+        // the maximum level)
+        vecTargetChannelLevel[i] = vecChannelsPerGroup[i] > 0 ?
+            targetLevelPerGroup - 20.0f * log10 ( vecChannelsPerGroup[i] ) :
+            0.0f;
+
+        // get median level
+        int cntChannels = levels[i].Size();
+        if ( cntChannels == 0 )
+        {
+            continue;
+        }
+        float refLevel = levels[i][cntChannels / 2];
+
+        // since we can only attenuate channels but not amplify, we have to
+        // check that the reference channel can be brought to the target
+        // level
+        if ( refLevel < vecTargetChannelLevel[i] )
+        {
+            // otherwise, we adjust the level offset in such a way that
+            // the level can be reached
+            levelOffset = fmin ( levelOffset,
+                refLevel - vecTargetChannelLevel[i] );
+
+            // compute the minimum necessary fader setting
+            minFader = fmin ( minFader, -vecMaxLevel[i] +
+                vecTargetChannelLevel[i] + levelOffset );
+        }
+    }
+
+    // take minimum fader value into account
+    // very weak channels would actually require strong channels to be
+    // attenuated to a large amount; however, the attenuation is limited by
+    // the faders
+    if ( minFader < -AUD_MIX_FADER_RANGE_DB )
+    {
+        levelOffset += -AUD_MIX_FADER_RANGE_DB - minFader;
+    }
+
+    // adjust all levels
+    for ( int i = 0; i < MAX_NUM_CHANNELS; ++i )
+    {
+        // only apply to visible faders (and not to my own channel fader)
+        if ( vecpChanFader[i]->IsVisible() && ( i != iMyChannelID ) )
+        {
+            // map averaged meter output level to decibels
+            // (invert CStereoSignalLevelMeter::CalcLogResultForMeter)
+            float leveldB = vecAvgLevels[i] *
+                ( UPPER_BOUND_SIG_METER - LOW_BOUND_SIG_METER ) /
+                NUM_STEPS_LED_BAR + LOW_BOUND_SIG_METER;
+
+            int group = vecpChanFader[i]->GetGroupID();
+            if ( group == INVALID_INDEX )
+            {
+                if ( cntActiveGroups > 0 )
+                {
+                    // do not adjust the channels without group in group mode
+                    continue;
+                }
+                else
+                {
+                    group = MAX_NUM_FADER_GROUPS;
+                }
+            }
+
+            // do not adjust channels with almost zero level to full level since
+            // the channel might simply be silent at the moment
+            if ( leveldB >= AUTO_FADER_NOISE_THRESHOLD_DB )
+            {
+                // compute new level
+                float newdBLevel = -leveldB + vecTargetChannelLevel[group] +
+                    levelOffset;
+
+                // map range from decibels to fader level
+                // (this inverts MathUtils::CalcFaderGain)
+                float newFaderLevel = ( newdBLevel / AUD_MIX_FADER_RANGE_DB +
+                    1.0f ) * AUD_MIX_FADER_MAX;
+
+                // limit fader
+                newFaderLevel = fmin ( fmax ( newFaderLevel, 0.0f),
+                    float ( AUD_MIX_FADER_MAX ) );
+
+                // set fader level
+                vecpChanFader[i]->SetFaderLevel ( newFaderLevel, true );
+            }
+        }
+    }
+}
+
 void CAudioMixerBoard::StoreAllFaderSettings()
 {
     QMutexLocker locker ( &Mutex );
@@ -1511,6 +1677,11 @@ void CAudioMixerBoard::SetChannelLevels ( const CVector<uint16_t>& vecChannelLev
     {
         if ( vecpChanFader[iChId]->IsVisible() && ( i < iNumChannelLevels ) )
         {
+            // compute exponential moving average
+            vecAvgLevels[iChId] =
+                (1.0f - AUTO_FADER_ADJUST_ALPHA) * vecAvgLevels[iChId] +
+                AUTO_FADER_ADJUST_ALPHA * vecChannelLevel[i];
+
             vecpChanFader[iChId]->SetChannelLevel ( vecChannelLevel[i++] );
 
             // show level only if we successfully received levels from the

src/audiomixerboard.h

@@ -232,6 +232,7 @@ class CAudioMixerBoard :
     void            SetAllFaderLevelsToNewClientLevel();
     void            StoreAllFaderSettings();
     void            LoadAllFaderSettings();
+    void            AutoAdjustAllFaderLevels();
 
 protected:
     class CMixerBoardScrollArea : public QScrollArea
@@ -276,6 +277,7 @@ class CAudioMixerBoard :
     ERecorderState          eRecorderState;
     QMutex                  Mutex;
     EChSortType             eChSortType;
+    CVector<float>          vecAvgLevels;
 
     virtual void UpdateGainValue ( const int    iChannelIdx,
                                    const float  fValue,

src/clientdlg.cpp

@@ -340,6 +340,8 @@ CClientDlg::CClientDlg ( CClient*         pNCliP,
     pEditMenu->addAction ( tr ( "Set All Faders to New Client &Level" ), this,
         SLOT ( OnSetAllFadersToNewClientLevel() ), QKeySequence ( Qt::CTRL + Qt::Key_L ) );
 
+    pEditMenu->addAction ( tr ( "Auto-Adjust all &Faders" ), this,
+        SLOT ( OnAutoAdjustAllFaderLevels() ), QKeySequence ( Qt::CTRL + Qt::Key_F ) );
 
     // Main menu bar -----------------------------------------------------------
     QMenuBar* pMenu = new QMenuBar ( this );

src/clientdlg.h

@@ -177,6 +177,7 @@ public slots:
     void OnUseTowRowsForMixerPanel ( bool Checked ) { MainMixerBoard->SetNumMixerPanelRows ( Checked ? 2 : 1 ); }
     void OnClearAllStoredSoloMuteSettings();
     void OnSetAllFadersToNewClientLevel() { MainMixerBoard->SetAllFaderLevelsToNewClientLevel(); }
+    void OnAutoAdjustAllFaderLevels() { MainMixerBoard->AutoAdjustAllFaderLevels(); }
 
     void OnSettingsStateChanged ( int value );
     void OnChatStateChanged ( int value );

src/global.h

@@ -152,6 +152,19 @@ LED bar:      lbr
 #define AUD_MIX_FADER_MAX                100
 #define AUD_MIX_PAN_MAX                  100
 
+// range of audio mixer fader
+#define AUD_MIX_FADER_RANGE_DB           35.0f
+
+// coefficient for averaging channel levels for automatic fader adjustment
+#define AUTO_FADER_ADJUST_ALPHA          0.2f
+
+// target level for auto fader adjustment in decibels
+#define AUTO_FADER_TARGET_LEVEL_DB       -30.0f
+
+// threshold in decibels below which the channel is considered as noise
+// and not adjusted
+#define AUTO_FADER_NOISE_THRESHOLD_DB    -40.0f
+
 // maximum number of fader groups (must be consistent to audiomixerboard implementation)
 #define MAX_NUM_FADER_GROUPS             4
 

src/util.cpp

@@ -485,6 +485,7 @@ CAboutDlg::CAboutDlg ( QWidget* parent ) : CBaseDlg ( parent )
         "<p>David Kastrup (<a href=\"https://github.com/dakhubgit\">dakhubgit</a>)</p>"
         "<p>Jordan Lum (<a href=\"https://github.com/mulyaj\">mulyaj</a>)</p>"
         "<p>Noam Postavsky (<a href=\"https://github.com/npostavs\">npostavs</a>)</p>"
+        "<p>Johannes Brauers (<a href=\"https://github.com/JohannesBrx\">JohannesBrx</a>)</p>"
         "<br>" + tr ( "For details on the contributions check out the " ) +
         "<a href=\"https://github.com/jamulussoftware/jamulus/graphs/contributors\">" + tr ( "Github Contributors list" ) + "</a>." );
 

src/util.h

@@ -1281,7 +1281,8 @@ class MathUtils
         }
         else
         {
-            return powf ( 10.0f, ( fInValueRange0_1 * 35.0f - 35.0f ) / 20.0f );
+            return powf ( 10.0f, ( fInValueRange0_1 - 1.0f ) *
+                AUD_MIX_FADER_RANGE_DB / 20.0f );
         }
     }
 };