tor-browser

commit fc84989374baf6eac06941c9c953e456ffec0ddc
parent dc3ebfbdcba61bf0e2e5eb14b592f6893f308906
Author: Karl Tomlinson <karlt+@karlt.net>
Date:   Wed,  8 Oct 2025 05:54:47 +0000

Bug 1992922 Clear scratch buffer on switch to fallback driver r=pehrsons

so that it is not output at an inappropriate later time.

Differential Revision: https://phabricator.services.mozilla.com/D267738

Diffstat:
M
dom/media/AudioBufferUtils.h
 | 
2
++
M
dom/media/GraphDriver.cpp
 | 
8
++++++++

2 files changed, 10 insertions(+), 0 deletions(-)
diff --git a/dom/media/AudioBufferUtils.h b/dom/media/AudioBufferUtils.h
@@ -167,6 +167,8 @@ class SpillBuffer {
     return this->operator=(aOther);
   }
 
+  bool IsEmpty() const { return mPosition == 0; }
+  void Empty() { mPosition = 0; }
   /* Empty the spill buffer into the buffer of the audio callback. This returns
    * the number of frames written. */
   uint32_t Empty(AudioCallbackBufferWrapper<T>& aBuffer) {
diff --git a/dom/media/GraphDriver.cpp b/dom/media/GraphDriver.cpp
@@ -866,6 +866,7 @@ long AudioCallbackDriver::DataCallback(const AudioDataValue* aInputBuffer,
 
   if (mAudioStreamState.compareExchange(AudioStreamState::Starting,
                                         AudioStreamState::Running)) {
+    MOZ_ASSERT(mScratchBuffer.IsEmpty());
     LOG(LogLevel::Verbose, ("%p: AudioCallbackDriver %p First audio callback "
                             "close the Fallback driver",
                             Graph(), this));
@@ -1296,6 +1297,13 @@ void AudioCallbackDriver::FallbackToSystemClockDriver() {
   LOG(LogLevel::Debug,
       ("%p: AudioCallbackDriver %p Falling back to SystemClockDriver.", Graph(),
        this));
+  // On DeviceChangedCallback() or StateChangeCallback(), mScratchBuffer might
+  // not be empty, but switching to a fallback driver is giving up on
+  // outputting mScratchBuffer contiguously.
+  // Clear the buffer so that it is not output later when an audio callback
+  // arrives for a new discontiguous output stream.
+  mScratchBuffer.Empty();
+
   mNextReInitBackoffStep =
       TimeDuration::FromMilliseconds(AUDIO_INITIAL_FALLBACK_BACKOFF_STEP_MS);
   mNextReInitAttempt = TimeStamp::Now() + mNextReInitBackoffStep;