From 0ddc112415d7d18de776d4868e1937ed12910b5b Mon Sep 17 00:00:00 2001
From: Paul Adenot <paul@paul.cx>
Date: Tue, 20 Oct 2020 20:03:26 +0000
Subject: [PATCH] Bug 1670917 - Add a pref to allow using raw WASAPI streams.
 Make it default to input-only raw streams. r=kinetik

Differential Revision: https://phabricator.services.mozilla.com/D93363
---
 dom/media/AudioStream.cpp                |  2 +-
 dom/media/CubebUtils.cpp                 | 15 ++++++++++-----
 dom/media/CubebUtils.h                   |  2 +-
 dom/media/GraphDriver.cpp                |  4 ++--
 modules/libpref/init/StaticPrefList.yaml | 13 +++++++++++++
 5 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/dom/media/AudioStream.cpp b/dom/media/AudioStream.cpp
index d7809ae69286..a765837a5945 100644
--- a/dom/media/AudioStream.cpp
+++ b/dom/media/AudioStream.cpp
@@ -286,7 +286,7 @@ nsresult AudioStream::Init(uint32_t aNumChannels,
   params.channels = mOutChannels;
   params.layout = static_cast<uint32_t>(aChannelMap);
   params.format = ToCubebFormat<AUDIO_OUTPUT_FORMAT>::value;
-  params.prefs = CubebUtils::GetDefaultStreamPrefs();
+  params.prefs = CubebUtils::GetDefaultStreamPrefs(CUBEB_DEVICE_TYPE_OUTPUT);
 
   // This is noop if MOZ_DUMP_AUDIO is not set.
   mDumpFile.Open("AudioStream", mOutChannels, aRate);
diff --git a/dom/media/CubebUtils.cpp b/dom/media/CubebUtils.cpp
index dbccbc4be1ab..0bd78835812c 100644
--- a/dom/media/CubebUtils.cpp
+++ b/dom/media/CubebUtils.cpp
@@ -39,6 +39,7 @@
 #include <cmath>
 #include <thread>
 #include "AudioThreadRegistry.h"
+#include "mozilla/StaticPrefs_media.h"
 
 #define AUDIOIPC_POOL_SIZE_DEFAULT 1
 #define AUDIOIPC_STACK_SIZE_DEFAULT (64 * 4096)
@@ -695,16 +696,20 @@ char* GetForcedOutputDevice() {
   return sCubebOutputDeviceName;
 }
 
-cubeb_stream_prefs GetDefaultStreamPrefs() {
+cubeb_stream_prefs GetDefaultStreamPrefs(cubeb_device_type aType) {
+  cubeb_stream_prefs prefs = CUBEB_STREAM_PREF_NONE;
 #ifdef XP_WIN
   // Investigation for bug 1427011 - if we're in E10S mode, rely on the
   // AudioNotification IPC to detect device changes.
   if (sCubebDisableDeviceSwitching &&
       (XRE_IsE10sParentProcess() || XRE_IsContentProcess())) {
-    return CUBEB_STREAM_PREF_DISABLE_DEVICE_SWITCHING;
+    prefs |= CUBEB_STREAM_PREF_DISABLE_DEVICE_SWITCHING;
+  }
+  if (StaticPrefs::media_cubeb_wasapi_raw() & static_cast<uint32_t>(aType)) {
+    prefs |= CUBEB_STREAM_PREF_RAW;
   }
 #endif
-  return CUBEB_STREAM_PREF_NONE;
+  return prefs;
 }
 
 bool RouteOutputAsVoice() { return sRouteOutputAsVoice; }
@@ -735,7 +740,7 @@ bool EstimatedRoundTripLatencyDefaultDevices(double* aMean, double* aStdDev) {
   output_params.rate = rate;
   output_params.channels = 2;
   output_params.layout = CUBEB_LAYOUT_UNDEFINED;
-  output_params.prefs = GetDefaultStreamPrefs();
+  output_params.prefs = GetDefaultStreamPrefs(CUBEB_DEVICE_TYPE_OUTPUT);
 
   latencyFrames = GetCubebMTGLatencyInFrames(&output_params);
 
@@ -744,7 +749,7 @@ bool EstimatedRoundTripLatencyDefaultDevices(double* aMean, double* aStdDev) {
   input_params.rate = rate;
   input_params.channels = 1;
   input_params.layout = CUBEB_LAYOUT_UNDEFINED;
-  input_params.prefs = GetDefaultStreamPrefs();
+  input_params.prefs = GetDefaultStreamPrefs(CUBEB_DEVICE_TYPE_INPUT);
 
   cubeb_stream* stm;
   rv = cubeb_stream_init(GetCubebContext(), &stm,
diff --git a/dom/media/CubebUtils.h b/dom/media/CubebUtils.h
index e9cb09aa6b01..7e024e3d92c5 100644
--- a/dom/media/CubebUtils.h
+++ b/dom/media/CubebUtils.h
@@ -54,7 +54,7 @@ uint32_t GetCubebPlaybackLatencyInMilliseconds();
 uint32_t GetCubebMTGLatencyInFrames(cubeb_stream_params* params);
 bool CubebLatencyPrefSet();
 void GetCurrentBackend(nsAString& aBackend);
-cubeb_stream_prefs GetDefaultStreamPrefs();
+cubeb_stream_prefs GetDefaultStreamPrefs(cubeb_device_type aType);
 char* GetForcedOutputDevice();
 // No-op on all platforms but Android, where it tells the device's AudioManager
 // to switch to "communication mode", which might change audio routing,
diff --git a/dom/media/GraphDriver.cpp b/dom/media/GraphDriver.cpp
index 639b2bd1acf8..cbf15b75d00e 100644
--- a/dom/media/GraphDriver.cpp
+++ b/dom/media/GraphDriver.cpp
@@ -636,7 +636,7 @@ void AudioCallbackDriver::Init() {
       AudioConfig::ChannelLayout(mOutputChannelCount).Map();
 
   output.layout = static_cast<uint32_t>(channelMap);
-  output.prefs = CubebUtils::GetDefaultStreamPrefs();
+  output.prefs = CubebUtils::GetDefaultStreamPrefs(CUBEB_DEVICE_TYPE_OUTPUT);
   if (mInputDevicePreference == CUBEB_DEVICE_PREF_VOICE &&
       CubebUtils::RouteOutputAsVoice()) {
     output.prefs |= static_cast<cubeb_stream_prefs>(CUBEB_STREAM_PREF_VOICE);
@@ -666,7 +666,7 @@ void AudioCallbackDriver::Init() {
   input = output;
   input.channels = mInputChannelCount;
   input.layout = CUBEB_LAYOUT_UNDEFINED;
-  input.prefs = CubebUtils::GetDefaultStreamPrefs();
+  input.prefs = CubebUtils::GetDefaultStreamPrefs(CUBEB_DEVICE_TYPE_INPUT);
   if (mInputDevicePreference == CUBEB_DEVICE_PREF_VOICE) {
     input.prefs |= static_cast<cubeb_stream_prefs>(CUBEB_STREAM_PREF_VOICE);
   }
diff --git a/modules/libpref/init/StaticPrefList.yaml b/modules/libpref/init/StaticPrefList.yaml
index f5f096c8fa7c..ec2095e64bfb 100644
--- a/modules/libpref/init/StaticPrefList.yaml
+++ b/modules/libpref/init/StaticPrefList.yaml
@@ -6829,6 +6829,19 @@
   value: false
 #endif
 
+# Whether or not to pass AUDCLNT_STREAMOPTIONS_RAW when initializing audio
+# streams when using WASAPI.
+# 0 - don't use RAW streams
+# 1 - use RAW streams for input streams only
+# 2 - use RAW streams for output streams only
+# 3 - use RAW streams for input and output streams
+#if defined (XP_WIN)
+- name: media.cubeb.wasapi-raw
+  type: RelaxedAtomicUint32
+  mirror: always
+  value: 1
+#endif // XP_WIN
+
 # ClockDrift desired buffering in milliseconds
 - name: media.clockdrift.buffering
   type: int32_t