Adding --mute.

src/xenia/apu/apu-private.h

@@ -14,4 +14,6 @@
 
 DECLARE_string(apu);
 
+DECLARE_bool(mute);
+
 #endif  // XENIA_APU_APU_PRIVATE_H_

src/xenia/apu/apu.cc

@@ -15,6 +15,8 @@ using namespace xe::apu;
 
 DEFINE_string(apu, "any", "Audio system. Use: [any, nop, xaudio2]");
 
+DEFINE_bool(mute, false, "Mutes all audio output.");
+
 #include "xenia/apu/nop/nop_apu.h"
 std::unique_ptr<AudioSystem> xe::apu::CreateNop(Emulator* emulator) {
   return xe::apu::nop::Create(emulator);

src/xenia/apu/xaudio2/xaudio2_audio_driver.cc

@@ -116,6 +116,10 @@ void XAudio2AudioDriver::Initialize() {
     return;
   }
 
+  if (FLAGS_mute) {
+    pcm_voice_->SetVolume(0.0f);
+  }
+
   SetEvent(wait_handle_);
 }