From 736b7f0d35d3dba2154dabd4f5d153e58a536c6c Mon Sep 17 00:00:00 2001
From: pkviet <pkv.stream@gmail.com>
Date: Sat, 10 Nov 2018 00:29:28 +0100
Subject: [PATCH] UI: Fix display of mono source with surround output

A mono input with surround output is upmixed by swresampler by routing
it to FC (front center) by default which corresponds to third channel
for 3.0, 4.0, 4.1, 5.0, 5.1, 7.1. (The other channels are muted.)
But the volume meters are set to show the first channel for mono sources.
Therefore although audio is processed, it would not show on the meter.
This fixes this display issue.

Closes obsproject/obs-studio#1540
---
 UI/volume-control.cpp | 24 ++++++++++++++++--------
 UI/volume-control.hpp |  1 +
 2 files changed, 17 insertions(+), 8 deletions(-)

diff --git a/UI/volume-control.cpp b/UI/volume-control.cpp
index 80fbe1f6e..525802a19 100644
--- a/UI/volume-control.cpp
+++ b/UI/volume-control.cpp
@@ -528,6 +528,8 @@ VolumeMeter::VolumeMeter(QWidget *parent, obs_volmeter_t *obs_volmeter,
 	peakHoldDuration = 20.0;                            //  20 seconds
 	inputPeakHoldDuration = 1.0;                        //  1 second
 
+	channels = (int)audio_output_get_channels(obs_get_audio());
+
 	handleChannelCofigurationChange();
 	updateTimerRef = updateTimer.toStrongRef();
 	if (!updateTimerRef) {
@@ -1007,16 +1009,22 @@ void VolumeMeter::paintEvent(QPaintEvent *event)
 
 	for (int channelNr = 0; channelNr < displayNrAudioChannels;
 		channelNr++) {
+
+		int channelNrFixed = (displayNrAudioChannels == 1 &&
+		                      channels > 2)
+			? 2
+			: channelNr;
+
 		if (vertical)
 			paintVMeter(painter, channelNr * 4, 8, 3, height - 10,
-					displayMagnitude[channelNr],
-					displayPeak[channelNr],
-					displayPeakHold[channelNr]);
+					displayMagnitude[channelNrFixed],
+					displayPeak[channelNrFixed],
+					displayPeakHold[channelNrFixed]);
 		else
 			paintHMeter(painter, 5, channelNr * 4, width - 5, 3,
-					displayMagnitude[channelNr],
-					displayPeak[channelNr],
-					displayPeakHold[channelNr]);
+					displayMagnitude[channelNrFixed],
+					displayPeak[channelNrFixed],
+					displayPeakHold[channelNrFixed]);
 
 		if (idle)
 			continue;
@@ -1026,10 +1034,10 @@ void VolumeMeter::paintEvent(QPaintEvent *event)
 		// having too much visual impact.
 		if (vertical)
 			paintInputMeter(painter, channelNr * 4, 3, 3, 3,
-					displayInputPeakHold[channelNr]);
+					displayInputPeakHold[channelNrFixed]);
 		else
 			paintInputMeter(painter, 0, channelNr * 4, 3, 3,
-					displayInputPeakHold[channelNr]);
+					displayInputPeakHold[channelNrFixed]);
 	}
 
 	lastRedrawTime = ts;
diff --git a/UI/volume-control.hpp b/UI/volume-control.hpp
index fde0d12f4..220cafcdf 100644
--- a/UI/volume-control.hpp
+++ b/UI/volume-control.hpp
@@ -144,6 +144,7 @@ private:
 	qreal inputPeakHoldDuration;
 
 	uint64_t lastRedrawTime = 0;
+	int channels = 0;
 	bool clipping = false;
 	bool vertical;