From 77178548f3541541db14b9bca00944b031094b16 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Marcin=20Smoczy=C5=84ski?= <smoczynski.marcin@gmail.com>
Date: Thu, 25 Mar 2021 00:19:15 +0100
Subject: [PATCH] [EGD-5260] Mono to stereo software conversion
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

Add workaround for Bluetooth audio to *always* convert mono PCM to
stereo.

Signed-off-by: Marcin Smoczyński <smoczynski.marcin@gmail.com>
---
 .../Audio/Operation/PlaybackOperation.cpp     |  7 +-----
 module-audio/Audio/decoder/Decoder.cpp        |  7 +++++-
 module-audio/Audio/decoder/DecoderWorker.cpp  | 23 +++++++++++++++----
 module-audio/Audio/decoder/DecoderWorker.hpp  |  9 +++++++-
 4 files changed, 33 insertions(+), 13 deletions(-)

diff --git a/module-audio/Audio/Operation/PlaybackOperation.cpp b/module-audio/Audio/Operation/PlaybackOperation.cpp
index 6f0a830703ee242592a3cf97f0867d4be98efb07..0eca39b3522b2bc4265775a344ddfbe0d87143e1 100644
--- a/module-audio/Audio/Operation/PlaybackOperation.cpp
+++ b/module-audio/Audio/Operation/PlaybackOperation.cpp
@@ -169,12 +169,7 @@ namespace audio
 
         // adjust new profile with information from file's tags
         newProfile->SetSampleRate(tags->sample_rate);
-        if (tags->num_channel == channel::stereoSound) {
-            newProfile->SetInOutFlags(static_cast<uint32_t>(AudioDevice::Flags::OutputStereo));
-        }
-        else {
-            newProfile->SetInOutFlags(static_cast<uint32_t>(AudioDevice::Flags::OutputMono));
-        }
+        newProfile->SetInOutFlags(static_cast<uint32_t>(AudioDevice::Flags::OutputStereo));
 
         // store profile
         currentProfile = newProfile;
diff --git a/module-audio/Audio/decoder/Decoder.cpp b/module-audio/Audio/decoder/Decoder.cpp
index cceaed5d3d4dfbb35b38410140b3ec1372b44873..5bae922b65a0166bc58f76961bbfa26f3b8f2481 100644
--- a/module-audio/Audio/decoder/Decoder.cpp
+++ b/module-audio/Audio/decoder/Decoder.cpp
@@ -126,7 +126,12 @@ namespace audio
     {
         assert(_stream != nullptr);
         if (!audioWorker) {
-            audioWorker = std::make_unique<DecoderWorker>(_stream, this, endOfFileCallback);
+            audioWorker =
+                std::make_unique<DecoderWorker>(_stream,
+                                                this,
+                                                endOfFileCallback,
+                                                tag->num_channel == 1 ? DecoderWorker::ChannelMode::ForceStereo
+                                                                      : DecoderWorker::ChannelMode::NoConversion);
             audioWorker->init();
             audioWorker->run();
         }
diff --git a/module-audio/Audio/decoder/DecoderWorker.cpp b/module-audio/Audio/decoder/DecoderWorker.cpp
index f8c275457c41f0965d25284939a52475966909ab..cf5c09d4db65bc6404b3d42797579f0d6d9c95db 100644
--- a/module-audio/Audio/decoder/DecoderWorker.cpp
+++ b/module-audio/Audio/decoder/DecoderWorker.cpp
@@ -4,10 +4,13 @@
 #include "DecoderWorker.hpp"
 #include "Audio/decoder/Decoder.hpp"
 
-audio::DecoderWorker::DecoderWorker(Stream *audioStreamOut, Decoder *decoder, EndOfFileCallback endOfFileCallback)
+audio::DecoderWorker::DecoderWorker(Stream *audioStreamOut,
+                                    Decoder *decoder,
+                                    EndOfFileCallback endOfFileCallback,
+                                    ChannelMode mode)
     : sys::Worker(DecoderWorker::workerName, DecoderWorker::workerPriority, stackDepth), audioStreamOut(audioStreamOut),
       decoder(decoder), endOfFileCallback(endOfFileCallback),
-      bufferSize(audioStreamOut->getBlockSize() / sizeof(BufferInternalType))
+      bufferSize(audioStreamOut->getBlockSize() / sizeof(BufferInternalType)), channelMode(mode)
 {}
 
 audio::DecoderWorker::~DecoderWorker()
@@ -84,17 +87,27 @@ bool audio::DecoderWorker::handleMessage(uint32_t queueID)
 
 void audio::DecoderWorker::pushAudioData()
 {
-    auto samplesRead = 0;
+    auto samplesRead             = 0;
+    const unsigned int readScale = channelMode == ChannelMode::ForceStereo ? 2 : 1;
 
     while (!audioStreamOut->isFull() && playbackEnabled) {
-        samplesRead = decoder->decode(bufferSize, decoderBuffer.get());
+        auto buffer = decoderBuffer.get();
+
+        samplesRead = decoder->decode(bufferSize / readScale, buffer);
 
         if (samplesRead == 0) {
             endOfFileCallback();
             break;
         }
 
-        if (!audioStreamOut->push(decoderBuffer.get(), samplesRead * sizeof(BufferInternalType))) {
+        // pcm mono to stereo force conversion
+        if (channelMode == ChannelMode::ForceStereo) {
+            for (unsigned int i = bufferSize / 2; i > 0; i--) {
+                buffer[i * 2 - 1] = buffer[i * 2 - 2] = buffer[i - 1];
+            }
+        }
+
+        if (!audioStreamOut->push(decoderBuffer.get(), samplesRead * sizeof(BufferInternalType) * readScale)) {
             LOG_FATAL("Decoder failed to push to stream.");
             break;
         }
diff --git a/module-audio/Audio/decoder/DecoderWorker.hpp b/module-audio/Audio/decoder/DecoderWorker.hpp
index 1b5a232f4092c3311315befd7cb53d1260124897..6008d0622e45d8803d344241f9bd2971c818a58d 100644
--- a/module-audio/Audio/decoder/DecoderWorker.hpp
+++ b/module-audio/Audio/decoder/DecoderWorker.hpp
@@ -21,7 +21,13 @@ namespace audio
             DisablePlayback,
         };
 
-        DecoderWorker(Stream *audioStreamOut, Decoder *decoder, EndOfFileCallback endOfFileCallback);
+        enum class ChannelMode
+        {
+            NoConversion,
+            ForceStereo
+        };
+
+        DecoderWorker(Stream *audioStreamOut, Decoder *decoder, EndOfFileCallback endOfFileCallback, ChannelMode mode);
         ~DecoderWorker() override;
 
         virtual auto init(std::list<sys::WorkerQueueInfo> queues = std::list<sys::WorkerQueueInfo>()) -> bool override;
@@ -52,5 +58,6 @@ namespace audio
 
         const int bufferSize;
         std::unique_ptr<BufferInternalType[]> decoderBuffer;
+        ChannelMode channelMode = ChannelMode::NoConversion;
     };
 } // namespace audio