From b6fbdf9aebcb0357792f2001bbd033b11e6bd381 Mon Sep 17 00:00:00 2001
From: Connor McLaughlin <stenzek@gmail.com>
Date: Sun, 10 May 2020 00:44:23 +1000
Subject: [PATCH] AudioStream: Support changing output volume

---
 src/common/audio_stream.cpp | 21 +++++++++++++++++++--
 src/common/audio_stream.h   | 14 ++++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/src/common/audio_stream.cpp b/src/common/audio_stream.cpp
index 0c0e816a3..e415ddacb 100644
--- a/src/common/audio_stream.cpp
+++ b/src/common/audio_stream.cpp
@@ -32,6 +32,12 @@ bool AudioStream::Reconfigure(u32 output_sample_rate /*= DefaultOutputSampleRate
   return true;
 }
 
+void AudioStream::SetOutputVolume(s32 volume)
+{
+  std::unique_lock<std::mutex> lock(m_buffer_mutex);
+  m_output_volume = volume;
+}
+
 void AudioStream::PauseOutput(bool paused)
 {
   if (m_output_paused == paused)
@@ -123,6 +129,16 @@ void AudioStream::EndWrite(u32 num_frames)
   m_buffer_mutex.unlock();
 }
 
+float AudioStream::GetMinLatency(u32 sample_rate, u32 buffer_size, u32 buffer_count)
+{
+  return (static_cast<float>(buffer_size) / static_cast<float>(sample_rate));
+}
+
+float AudioStream::GetMaxLatency(u32 sample_rate, u32 buffer_size, u32 buffer_count)
+{
+  return (static_cast<float>(buffer_size * (buffer_count - 1)) / static_cast<float>(sample_rate));
+}
+
 u32 AudioStream::GetSamplesAvailable() const
 {
   // TODO: Use atomic loads
@@ -146,8 +162,9 @@ u32 AudioStream::ReadSamples(SampleType* samples, u32 num_samples)
     const u32 from_this_buffer = std::min(m_buffer_size - buffer.read_position, remaining_samples);
 
     const u32 copy_count = from_this_buffer * m_channels;
-    std::memcpy(samples, &buffer.data[buffer.read_position * m_channels], copy_count * sizeof(SampleType));
-    samples += copy_count;
+    const SampleType* read_pointer = &buffer.data[buffer.read_position * m_channels];
+    for (u32 i = 0; i < copy_count; i++)
+      *(samples++) = ApplyVolume(*(read_pointer++), m_output_volume);
 
     remaining_samples -= from_this_buffer;
     buffer.read_position += from_this_buffer;
diff --git a/src/common/audio_stream.h b/src/common/audio_stream.h
index 030bc28d2..0e00c2a3b 100644
--- a/src/common/audio_stream.h
+++ b/src/common/audio_stream.h
@@ -26,11 +26,13 @@ public:
   u32 GetChannels() const { return m_channels; }
   u32 GetBufferSize() const { return m_buffer_size; }
   u32 GetBufferCount() const { return static_cast<u32>(m_buffers.size()); }
+  s32 GetOutputVolume() const { return m_output_volume; }
   bool IsSyncing() const { return m_sync; }
 
   bool Reconfigure(u32 output_sample_rate = DefaultOutputSampleRate, u32 channels = 1,
                    u32 buffer_size = DefaultBufferSize, u32 buffer_count = DefaultBufferCount);
   void SetSync(bool enable) { m_sync = enable; }
+  void SetOutputVolume(s32 volume);
 
   void PauseOutput(bool paused);
   void EmptyBuffers();
@@ -45,12 +47,21 @@ public:
 
   static std::unique_ptr<AudioStream> CreateCubebAudioStream();
 
+  // Latency computation - returns values in seconds
+  static float GetMinLatency(u32 sample_rate, u32 buffer_size, u32 buffer_count);
+  static float GetMaxLatency(u32 sample_rate, u32 buffer_size, u32 buffer_count);
+
 protected:
   virtual bool OpenDevice() = 0;
   virtual void PauseDevice(bool paused) = 0;
   virtual void CloseDevice() = 0;
   virtual void BufferAvailable() = 0;
 
+  ALWAYS_INLINE static SampleType ApplyVolume(SampleType sample, s32 volume)
+  {
+    return s16((s32(sample) * volume) / 100);
+  }
+
   bool IsDeviceOpen() const { return (m_output_sample_rate > 0); }
 
   u32 GetSamplesAvailable() const;
@@ -87,6 +98,9 @@ private:
   // TODO: Switch to semaphore
   std::condition_variable m_buffer_available_cv;
 
+  // volume, 0-100
+  s32 m_output_volume = 100;
+
   bool m_output_paused = true;
   bool m_sync = true;
 };
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