Fix timestretch AV sync

    ALOGV("processFrames(%zu %zu)  remaining(%zu)", *dstFrames, *srcFrames, mRemaining);

    // Note dstFrames is the required number of frames.

    if (!mAudioPlaybackRateValid) {

        //fallback mode

        // Ensure consumption from src is as expected.

        // TODO: add logic to track "very accurate" consumption related to speed, original sampling

        // rate, actual frames processed.

        const size_t targetSrc = *dstFrames * mPlaybackRate.mSpeed;

        if (*srcFrames < targetSrc) { // limit dst frames to that possible

            *dstFrames = *srcFrames / mPlaybackRate.mSpeed;

        } else if (*srcFrames > targetSrc + 1) {

            *srcFrames = targetSrc + 1;

        }

    if (!mAudioPlaybackRateValid) {

        //fallback mode

        if (*dstFrames > 0) {

            switch(mPlaybackRate.mFallbackMode) {

            case AUDIO_TIMESTRETCH_FALLBACK_CUT_REPEAT: