From 7519da5e13ff72a43d05a8a1632d0becb33d457b Mon Sep 17 00:00:00 2001
From: Rene Stange <rsta2@o2online.de>
Date: Mon, 21 Mar 2022 19:02:29 +0100
Subject: [PATCH] Fix Stereo channel swap with HDMI (#52)

There has been a swap of the Stereo channels with HDMI. With the new
option "ChannelsSwapped=0|1" in minidexed.ini one can swap the channels
again, in case it is needed.
---
 src/config.cpp    |  6 ++++++
 src/config.h      |  2 ++
 src/minidexed.cpp | 17 +++++++++++++++--
 src/minidexed.h   |  1 +
 src/minidexed.ini |  1 +
 5 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/src/config.cpp b/src/config.cpp
index 0242548a..d8ba0cf1 100644
--- a/src/config.cpp
+++ b/src/config.cpp
@@ -44,6 +44,7 @@ void CConfig::Load (void)
 	m_nChunkSize = m_Properties.GetNumber ("ChunkSize", m_SoundDevice == "hdmi" ? 384*6 : 1024);
 #endif
 	m_nDACI2CAddress = m_Properties.GetNumber ("DACI2CAddress", 0);
+	m_bChannelsSwapped = m_Properties.GetNumber ("ChannelsSwapped", 0) != 0;
 
 	m_nMIDIBaudRate = m_Properties.GetNumber ("MIDIBaudRate", 31250);
 
@@ -85,6 +86,11 @@ unsigned CConfig::GetDACI2CAddress (void) const
 	return m_nDACI2CAddress;
 }
 
+bool CConfig::GetChannelsSwapped (void) const
+{
+	return m_bChannelsSwapped;
+}
+
 unsigned CConfig::GetMIDIBaudRate (void) const
 {
 	return m_nMIDIBaudRate;
diff --git a/src/config.h b/src/config.h
index f94e62ed..2b24ffcf 100644
--- a/src/config.h
+++ b/src/config.h
@@ -67,6 +67,7 @@ class CConfig		// Configuration for MiniDexed
 	unsigned GetSampleRate (void) const;
 	unsigned GetChunkSize (void) const;
 	unsigned GetDACI2CAddress (void) const;		// 0 for auto probing
+	bool GetChannelsSwapped (void) const;
 
 	// MIDI
 	unsigned GetMIDIBaudRate (void) const;
@@ -100,6 +101,7 @@ class CConfig		// Configuration for MiniDexed
 	unsigned m_nSampleRate;
 	unsigned m_nChunkSize;
 	unsigned m_nDACI2CAddress;
+	bool m_bChannelsSwapped;
 
 	unsigned m_nMIDIBaudRate;
 
diff --git a/src/minidexed.cpp b/src/minidexed.cpp
index df37609b..a8284d16 100644
--- a/src/minidexed.cpp
+++ b/src/minidexed.cpp
@@ -41,6 +41,7 @@ CMiniDexed::CMiniDexed (CConfig *pConfig, CInterruptSystem *pInterrupt,
 	m_SerialMIDI (this, pInterrupt, pConfig),
 	m_bUseSerial (false),
 	m_pSoundDevice (0),
+	m_bChannelsSwapped (pConfig->GetChannelsSwapped ()),
 #ifdef ARM_ALLOW_MULTI_CORE
 	m_nActiveTGsLog2 (0),
 #endif
@@ -83,6 +84,10 @@ CMiniDexed::CMiniDexed (CConfig *pConfig, CInterruptSystem *pInterrupt,
 
 		m_pSoundDevice = new CHDMISoundBaseDevice (pInterrupt, pConfig->GetSampleRate (),
 							   pConfig->GetChunkSize ());
+
+		// The channels are swapped by default in the HDMI sound driver.
+		// TODO: Remove this line, when this has been fixed in the driver.
+		m_bChannelsSwapped = !m_bChannelsSwapped;
 	}
 	else
 	{
@@ -512,8 +517,16 @@ void CMiniDexed::ProcessSound (void)
 					 + m_OutputLevel[7][i] * m_nPan[7];
 			nRight >>= m_nActiveTGsLog2 + 7;
 
-			SampleBuffer[i][0] = (int16_t) nLeft;
-			SampleBuffer[i][1] = (int16_t) nRight;
+			if (!m_bChannelsSwapped)
+			{
+				SampleBuffer[i][0] = (int16_t) nLeft;
+				SampleBuffer[i][1] = (int16_t) nRight;
+			}
+			else
+			{
+				SampleBuffer[i][0] = (int16_t) nRight;
+				SampleBuffer[i][1] = (int16_t) nLeft;
+			}
 		}
 
 		if (   m_pSoundDevice->Write (SampleBuffer, sizeof SampleBuffer)
diff --git a/src/minidexed.h b/src/minidexed.h
index b592af72..daf9acba 100644
--- a/src/minidexed.h
+++ b/src/minidexed.h
@@ -103,6 +103,7 @@ class CMiniDexed
 	bool m_bUseSerial;
 
 	CSoundBaseDevice *m_pSoundDevice;
+	bool m_bChannelsSwapped;
 	unsigned m_nQueueSizeFrames;
 
 #ifdef ARM_ALLOW_MULTI_CORE
diff --git a/src/minidexed.ini b/src/minidexed.ini
index 9b5b10ec..cd2123ac 100644
--- a/src/minidexed.ini
+++ b/src/minidexed.ini
@@ -7,6 +7,7 @@ SoundDevice=pwm
 SampleRate=48000
 #ChunkSize=256
 DACI2CAddress=0
+ChannelsSwapped=0
 
 # MIDI
 MIDIBaudRate=31250