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Commit c8e09c61 authored by Andy Hung's avatar Andy Hung
Browse files

Improve AudioTrack offload timestamp startup glitch detector 

New or existing glitch behavior for Nexus 5 offload audio:
we receive several 0 timestamps,
then we get a stale timestamp (very large),
then a few ms later we get a correct nonzero timestamp.

We attempt to hide the glitch because the retrograde timestamp
correction makes the glitch "sticky".

Bug: 21633313
Change-Id: I39153af718c151f9435e7d315651a811f72743da
parent 005e9d03

include/media/AudioTrack.h

+1 −0
Original line number Diff line number Diff line
@@ -894,6 +894,7 @@ protected: 
                                                    // only used for offloaded and direct tracks.



    bool                    mPreviousTimestampValid;// true if mPreviousTimestamp is valid

    bool                    mTimestampStartupGlitchReported; // reduce log spam

    bool                    mRetrogradeMotionReported; // reduce log spam

    AudioTimestamp          mPreviousTimestamp;     // used to detect retrograde motion

media/libmedia/AudioTrack.cpp

+26 −4
Original line number Diff line number Diff line
@@ -492,6 +492,8 @@ status_t AudioTrack::set( 
    mObservedSequence = mSequence;

    mInUnderrun = false;

    mPreviousTimestampValid = false;

    mTimestampStartupGlitchReported = false;

    mRetrogradeMotionReported = false;



    return NO_ERROR;

}
@@ -519,6 +521,8 @@ status_t AudioTrack::start() 
        // reset current position as seen by client to 0

        mPosition = 0;

        mPreviousTimestampValid = false;

        mTimestampStartupGlitchReported = false;

        mRetrogradeMotionReported = false;



        // For offloaded tracks, we don't know if the hardware counters are really zero here,

        // since the flush is asynchronous and stop may not fully drain.
@@ -2218,7 +2222,12 @@ status_t AudioTrack::getTimestamp(AudioTimestamp& timestamp) 
        }



        // Check whether a pending flush or stop has completed, as those commands may

        // be asynchronous or return near finish.

        // be asynchronous or return near finish or exhibit glitchy behavior.

        //

        // Originally this showed up as the first timestamp being a continuation of

        // the previous song under gapless playback.

        // However, we sometimes see zero timestamps, then a glitch of

        // the previous song's position, and then correct timestamps afterwards.

        if (mStartUs != 0 && mSampleRate != 0) {

            static const int kTimeJitterUs = 100000; // 100 ms

            static const int k1SecUs = 1000000;
@@ -2236,16 +2245,29 @@ status_t AudioTrack::getTimestamp(AudioTimestamp& timestamp) 


                if (deltaPositionByUs > deltaTimeUs + kTimeJitterUs) {

                    // Verify that the counter can't count faster than the sample rate

                    // since the start time.  If greater, then that means we have failed

                    // since the start time.  If greater, then that means we may have failed

                    // to completely flush or stop the previous playing track.

                    ALOGW("incomplete flush or stop:"

                    ALOGW_IF(!mTimestampStartupGlitchReported,

                            "getTimestamp startup glitch detected"

                            " deltaTimeUs(%lld) deltaPositionUs(%lld) tsmPosition(%u)",

                            (long long)deltaTimeUs, (long long)deltaPositionByUs,

                            timestamp.mPosition);

                    mTimestampStartupGlitchReported = true;

                    if (previousTimestampValid

                            && mPreviousTimestamp.mPosition == 0 /* should be true if valid */) {

                        timestamp = mPreviousTimestamp;

                        mPreviousTimestampValid = true;

                        return NO_ERROR;

                    }

                    return WOULD_BLOCK;

                }

                if (deltaPositionByUs != 0) {

                    mStartUs = 0; // don't check again, we got valid nonzero position.

                }

            } else {

                mStartUs = 0; // don't check again, start time expired.

            }

            mStartUs = 0; // no need to check again, start timestamp has either expired or unneeded.

            mTimestampStartupGlitchReported = false;

        }

    } else {

        // Update the mapping between local consumed (mPosition) and server consumed (mServer)