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Commit 0cae043f authored by Atneya Nair's avatar Atneya Nair
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Allow frame count regress in AudioStreamOut 

AudioStreamOut attempts to detect wraparound by assuming that the
HAL frame count is monotonic, which is not true wrt gapless offload
tracks. When a non-monotonic update is detected, we freeze the fw
side framecount, rather than updating. The exception is when we
are notified that framecount will reset (e.g. flush()).

Since the notification that we are transitioning can occur arbitrarily
in advance from the HAL, upon presentationComplete for a offload stream,
we notify AudioStreamOut that we expect an upcoming framecount reset
from the HAL.
Then, we do not suppress the next detected non-monotonic sample, and
appropriately decrease the uint64 mRenderPosition.

Test: offloadAudioTrackPlayer manual test app (exoplayer test in
google3)

Bug: 191950723
Change-Id: I6060d0a9750783c2e2a7b46ce592c042d1405aa0
parent 688cec6e

services/audioflinger/AudioStreamOut.cpp

+7 −0
Original line number Diff line number Diff line
@@ -39,6 +39,7 @@ AudioStreamOut::AudioStreamOut(AudioHwDevice *dev, audio_output_flags_t flags) 
        , mRateMultiplier(1)

        , mHalFormatHasProportionalFrames(false)

        , mHalFrameSize(0)

        , mExpectRetrograde(false)

{

}
@@ -69,8 +70,12 @@ status_t AudioStreamOut::getRenderPosition(uint64_t *frames) 
    const uint32_t truncatedPosition = (uint32_t)mRenderPosition;

    int32_t deltaHalPosition; // initialization not needed, overwitten by __builtin_sub_overflow()

    (void) __builtin_sub_overflow(halPosition, truncatedPosition, &deltaHalPosition);



    if (deltaHalPosition > 0) {

        mRenderPosition += deltaHalPosition;

    } else if (mExpectRetrograde) {

        mExpectRetrograde = false;

        mRenderPosition -= static_cast<uint64_t>(-deltaHalPosition);

    }

    // Scale from HAL sample rate to application rate.

    *frames = mRenderPosition / mRateMultiplier;
@@ -187,6 +192,7 @@ audio_config_base_t AudioStreamOut::getAudioProperties() const 
int AudioStreamOut::flush()

{

    mRenderPosition = 0;

    mExpectRetrograde = false;

    mFramesWritten = 0;

    mFramesWrittenAtStandby = 0;

    status_t result = stream->flush();
@@ -196,6 +202,7 @@ int AudioStreamOut::flush() 
int AudioStreamOut::standby()

{

    mRenderPosition = 0;

    mExpectRetrograde = false;

    mFramesWrittenAtStandby = mFramesWritten;

    return stream->standby();

}

services/audioflinger/AudioStreamOut.h

+9 −1
Original line number Diff line number Diff line
@@ -93,13 +93,21 @@ public: 
    virtual status_t flush();

    virtual status_t standby();



    // Avoid suppressing retrograde motion in mRenderPosition for gapless offload/direct when

    // transitioning between tracks.

    // The HAL resets the frame position without flush/stop being called, but calls back prior to

    // this event. So, on the next occurrence of retrograde motion, we permit backwards movement of

    // mRenderPosition.

    virtual void presentationComplete() { mExpectRetrograde = true; }



protected:

    uint64_t             mFramesWritten; // reset by flush

    uint64_t             mFramesWrittenAtStandby;

    uint64_t             mRenderPosition; // reset by flush or standby

    uint64_t             mRenderPosition; // reset by flush, standby, or presentation complete

    int                  mRateMultiplier;

    bool                 mHalFormatHasProportionalFrames;

    size_t               mHalFrameSize;

    bool                 mExpectRetrograde; // see presentationComplete

};



} // namespace android

services/audioflinger/Threads.cpp

+7 −2
Original line number Diff line number Diff line
@@ -6320,9 +6320,13 @@ AudioFlinger::PlaybackThread::mixer_state AudioFlinger::DirectOutputThread::prep 
                    track->isStopping_2() || track->isPaused()) {

                // We have consumed all the buffers of this track.

                // Remove it from the list of active tracks.

                bool presComplete = false;

                if (mStandby || !last ||

                        track->presentationComplete(latency_l()) ||

                        (presComplete = track->presentationComplete(latency_l())) ||

                        track->isPaused() || mHwPaused) {

                    if (presComplete) {

                        mOutput->presentationComplete();

                    }

                    if (track->isStopping_2()) {

                        track->mState = TrackBase::STOPPED;

                    }
@@ -6901,7 +6905,8 @@ AudioFlinger::PlaybackThread::mixer_state AudioFlinger::OffloadThread::prepareTr 
                // Drain has completed or we are in standby, signal presentation complete

                if (!(mDrainSequence & 1) || !last || mStandby) {

                    track->mState = TrackBase::STOPPED;

                    track->presentationComplete(latency_l());

                    mOutput->presentationComplete();

                    track->presentationComplete(latency_l()); // always returns true

                    track->reset();

                    tracksToRemove->add(track);

                    // OFFLOADED stop resets frame counts.