Bug 1887774 add prefs to simulate drift in audio streams r=padenot

Differential Revision: https://phabricator.services.mozilla.com/D206863

dom/media/CubebUtils.cpp

@@ -382,10 +382,33 @@ int CubebStreamInit(cubeb* context, cubeb_stream** stream,
   if (ms) {
     std::this_thread::sleep_for(std::chrono::milliseconds(ms));
   }
-  return cubeb_stream_init(context, stream, stream_name, input_device,
-                           input_stream_params, output_device,
-                           output_stream_params, latency_frames, data_callback,
-                           state_callback, user_ptr);
+  cubeb_stream_params inputParamData;
+  cubeb_stream_params outputParamData;
+  cubeb_stream_params* inputParamPtr = input_stream_params;
+  cubeb_stream_params* outputParamPtr = output_stream_params;
+  if (input_stream_params && !output_stream_params) {
+    inputParamData = *input_stream_params;
+    inputParamData.rate = llround(
+        static_cast<double>(StaticPrefs::media_cubeb_input_drift_factor()) *
+        inputParamData.rate);
+    MOZ_LOG(
+        gCubebLog, LogLevel::Info,
+        ("CubebStreamInit input stream rate %" PRIu32, inputParamData.rate));
+    inputParamPtr = &inputParamData;
+  } else if (output_stream_params && !input_stream_params) {
+    outputParamData = *output_stream_params;
+    outputParamData.rate = llround(
+        static_cast<double>(StaticPrefs::media_cubeb_output_drift_factor()) *
+        outputParamData.rate);
+    MOZ_LOG(
+        gCubebLog, LogLevel::Info,
+        ("CubebStreamInit output stream rate %" PRIu32, outputParamData.rate));
+    outputParamPtr = &outputParamData;
+  }
+
+  return cubeb_stream_init(
+      context, stream, stream_name, input_device, inputParamPtr, output_device,
+      outputParamPtr, latency_frames, data_callback, state_callback, user_ptr);
 }
 
 void InitBrandName() {

modules/libpref/init/StaticPrefList.yaml

@@ -9592,6 +9592,20 @@
   value: 32768   # Measured in KiB
   mirror: always
 
+# Multiplier to change the sample rate at which input-only streams run, so as
+# to similate clock drift.
+- name: media.cubeb.input_drift_factor
+  type: AtomicFloat
+  mirror: always
+  value: 1.f
+
+# Multiplier to change the sample rate at which output-only streams run, so as
+# to similate clock drift.
+- name: media.cubeb.output_drift_factor
+  type: AtomicFloat
+  mirror: always
+  value: 1.f
+
 # Whether cubeb is sandboxed (AudioIPC)
 - name: media.cubeb.sandbox
   type: bool