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Commit 6140c79c authored by Phil Burk's avatar Phil Burk
Browse files

AudioFlinger: prevent retrograde timestamps for direct mode 



Prevent retrograde motion in the HAL or drivers from making it
up through the AudioFlinger to the app.

Bug: 19604395
Change-Id: I11d6c0f7cab69e75fd4b4a2a90f64960b4bb6d5a
Signed-off-by: default avatarPhil Burk <philburk@google.com>
parent 377165c2

services/audioflinger/PlaybackTracks.h

+3 −2
Original line number Diff line number Diff line
@@ -157,8 +157,9 @@ private: 
    bool                mFlushHwPending; // track requests for thread flush



    // for last call to getTimestamp

    bool                mPreviousValid;

    uint32_t            mPreviousFramesWritten;

    bool                mPreviousTimestampValid;

    // This is either the first timestamp or one that has passed

    // the check to prevent retrograde motion.

    AudioTimestamp      mPreviousTimestamp;

};  // end of Track

services/audioflinger/Tracks.cpp

+48 −29
Original line number Diff line number Diff line
@@ -405,9 +405,7 @@ AudioFlinger::PlaybackThread::Track::Track( 
    mAudioTrackServerProxy(NULL),

    mResumeToStopping(false),

    mFlushHwPending(false),

    mPreviousValid(false),

    mPreviousFramesWritten(0)

    // mPreviousTimestamp

    mPreviousTimestampValid(false)

{

    // client == 0 implies sharedBuffer == 0

    ALOG_ASSERT(!(client == 0 && sharedBuffer != 0));
@@ -864,7 +862,7 @@ void AudioFlinger::PlaybackThread::Track::reset() 
        if (mState == FLUSHED) {

            mState = IDLE;

        }

        mPreviousValid = false;

        mPreviousTimestampValid = false;

    }

}
@@ -886,19 +884,22 @@ status_t AudioFlinger::PlaybackThread::Track::getTimestamp(AudioTimestamp& times 
{

    // Client should implement this using SSQ; the unpresented frame count in latch is irrelevant

    if (isFastTrack()) {

        // FIXME no lock held to set mPreviousValid = false

        // FIXME no lock held to set mPreviousTimestampValid = false

        return INVALID_OPERATION;

    }

    sp<ThreadBase> thread = mThread.promote();

    if (thread == 0) {

        // FIXME no lock held to set mPreviousValid = false

        // FIXME no lock held to set mPreviousTimestampValid = false

        return INVALID_OPERATION;

    }



    Mutex::Autolock _l(thread->mLock);

    PlaybackThread *playbackThread = (PlaybackThread *)thread.get();



    status_t result = INVALID_OPERATION;

    if (!isOffloaded() && !isDirect()) {

        if (!playbackThread->mLatchQValid) {

            mPreviousValid = false;

            mPreviousTimestampValid = false;

            return INVALID_OPERATION;

        }

        uint32_t unpresentedFrames =
@@ -914,36 +915,54 @@ status_t AudioFlinger::PlaybackThread::Track::getTimestamp(AudioTimestamp& times 
        uint32_t framesWritten = i >= 0 ?

                playbackThread->mLatchQ.mFramesReleased[i] :

                mAudioTrackServerProxy->framesReleased();

        bool checkPreviousTimestamp = mPreviousValid && framesWritten >= mPreviousFramesWritten;

        if (framesWritten < unpresentedFrames) {

            mPreviousValid = false;

            return INVALID_OPERATION;

            mPreviousTimestampValid = false;

            // return invalid result

        } else {

            timestamp.mPosition = framesWritten - unpresentedFrames;

            timestamp.mTime = playbackThread->mLatchQ.mTimestamp.mTime;

            result = NO_ERROR;

        }

        mPreviousFramesWritten = framesWritten;

        uint32_t position = framesWritten - unpresentedFrames;

        struct timespec time = playbackThread->mLatchQ.mTimestamp.mTime;

        if (checkPreviousTimestamp) {

            if (time.tv_sec < mPreviousTimestamp.mTime.tv_sec ||

                    (time.tv_sec == mPreviousTimestamp.mTime.tv_sec &&

                    time.tv_nsec < mPreviousTimestamp.mTime.tv_nsec)) {

                ALOGW("Time is going backwards");

    } else { // offloaded or direct

        result = playbackThread->getTimestamp_l(timestamp);

    }



    // Prevent retrograde motion in timestamp.

    if (result == NO_ERROR) {

        if (mPreviousTimestampValid) {

            if (timestamp.mTime.tv_sec < mPreviousTimestamp.mTime.tv_sec ||

                    (timestamp.mTime.tv_sec == mPreviousTimestamp.mTime.tv_sec &&

                    timestamp.mTime.tv_nsec < mPreviousTimestamp.mTime.tv_nsec)) {

                ALOGW("WARNING - retrograde timestamp time");

                // FIXME Consider blocking this from propagating upwards.

            }



            // Looking at signed delta will work even when the timestamps

            // are wrapping around.

            int32_t deltaPosition = static_cast<int32_t>(timestamp.mPosition

                    - mPreviousTimestamp.mPosition);

            // position can bobble slightly as an artifact; this hides the bobble

            static const uint32_t MINIMUM_POSITION_DELTA = 8u;

            if ((position <= mPreviousTimestamp.mPosition) ||

                    (position - mPreviousTimestamp.mPosition) < MINIMUM_POSITION_DELTA) {

                position = mPreviousTimestamp.mPosition;

                time = mPreviousTimestamp.mTime;

            static const int32_t MINIMUM_POSITION_DELTA = 8;

            if (deltaPosition < 0) {

#define TIME_TO_NANOS(time) ((uint64_t)time.tv_sec * 1000000000 + time.tv_nsec)

                ALOGW("WARNING - retrograde timestamp position corrected,"

                        " %d = %u - %u, (at %llu, %llu nanos)",

                        deltaPosition,

                        timestamp.mPosition,

                        mPreviousTimestamp.mPosition,

                        TIME_TO_NANOS(timestamp.mTime),

                        TIME_TO_NANOS(mPreviousTimestamp.mTime));

#undef TIME_TO_NANOS

            }

            if (deltaPosition < MINIMUM_POSITION_DELTA) {

                // Current timestamp is bad. Use last valid timestamp.

                timestamp = mPreviousTimestamp;

            }

        }

        timestamp.mPosition = position;

        timestamp.mTime = time;

        mPreviousTimestamp = timestamp;

        mPreviousValid = true;

        return NO_ERROR;

        mPreviousTimestampValid = true;

    }



    return playbackThread->getTimestamp_l(timestamp);

    return result;

}



status_t AudioFlinger::PlaybackThread::Track::attachAuxEffect(int EffectId)