diff --git a/libxenia.vcxproj b/libxenia.vcxproj
index ed3e129fc..37c87626c 100644
--- a/libxenia.vcxproj
+++ b/libxenia.vcxproj
@@ -16,7 +16,7 @@
   </ItemGroup>
   <ItemGroup>
     <ClCompile Include="src\xenia\apu\apu.cc" />
-    <ClCompile Include="src\xenia\apu\audio_decoder.cpp" />
+    <ClCompile Include="src\xenia\apu\audio_decoder.cc" />
     <ClCompile Include="src\xenia\apu\audio_driver.cc" />
     <ClCompile Include="src\xenia\apu\audio_system.cc" />
     <ClCompile Include="src\xenia\apu\nop\nop_apu.cc" />
diff --git a/libxenia.vcxproj.filters b/libxenia.vcxproj.filters
index a9990fa36..563796688 100644
--- a/libxenia.vcxproj.filters
+++ b/libxenia.vcxproj.filters
@@ -706,6 +706,9 @@
     <ClCompile Include="src\xenia\cpu\backend\x64\x64_code_cache.cc">
       <Filter>src\xenia\cpu\backend\x64</Filter>
     </ClCompile>
+    <ClCompile Include="src\xenia\apu\audio_decoder.cc">
+      <Filter>src\xenia\apu</Filter>
+    </ClCompile>
   </ItemGroup>
   <ItemGroup>
     <ClInclude Include="src\xenia\emulator.h">
diff --git a/src/xenia/apu/audio_decoder.cpp b/src/xenia/apu/audio_decoder.cc
similarity index 100%
rename from src/xenia/apu/audio_decoder.cpp
rename to src/xenia/apu/audio_decoder.cc
diff --git a/src/xenia/apu/audio_system.h b/src/xenia/apu/audio_system.h
index 1aac86224..27c748093 100644
--- a/src/xenia/apu/audio_system.h
+++ b/src/xenia/apu/audio_system.h
@@ -62,9 +62,9 @@ struct XMAContextData {
   uint32_t loop_subframe_skip : 3;           // +17bit, XMASetLoopData might be subframe_decode_count
   uint32_t subframe_decode_count : 4;        // +20bit might be subframe_skip_count
   uint32_t unk_dword_1_b : 3;                // ? NumSubframesToSkip/NumChannels(?)
-  uint32_t sample_rate : 2;                  // +27bit multiplied by something?
+  uint32_t sample_rate : 2;                  // +27bit enum of sample rates
   uint32_t is_stereo : 1;                    // +29bit might be NumChannels
-  uint32_t unk_dword_1_c : 1;                // ? NumChannels?
+  uint32_t unk_dword_1_c : 1;                // ? part of NumChannels?
   uint32_t output_buffer_valid : 1;          // +31bit, XMAIsOutputBufferValid
 
   // DWORD 2