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Commit 97844998 authored by Chong Zhang's avatar Chong Zhang
Browse files

HLS: reduce number of guessed wrong seq numbers 

- account for playlist age in live streaming when calculating
  segment time

- be more conservative on downswitching if bandwidth is unstable

- adjust forward or backward if guessed wrong seq number

- code refactor

bug: 19567254

Change-Id: I0b61cea888fdffd1b3ee2446747ed10152e9e7d7
parent 2170233c

include/media/stagefright/Utils.h

+1 −1
Original line number Diff line number Diff line
@@ -71,7 +71,7 @@ struct HLSTime { 
    sp<AMessage> mMeta;



    HLSTime(const sp<AMessage> &meta = NULL);

    int64_t getSegmentTimeUs(bool midpoint = false) const;

    int64_t getSegmentTimeUs() const;

};



bool operator <(const HLSTime &t0, const HLSTime &t1);

media/libstagefright/Utils.cpp

+21 −3
Original line number Diff line number Diff line
@@ -852,14 +852,32 @@ HLSTime::HLSTime(const sp<AMessage>& meta) : 
    }

}



int64_t HLSTime::getSegmentTimeUs(bool midpoint) const {

int64_t HLSTime::getSegmentTimeUs() const {

    int64_t segmentStartTimeUs = -1ll;

    if (mMeta != NULL) {

        CHECK(mMeta->findInt64("segmentStartTimeUs", &segmentStartTimeUs));

        if (midpoint) {



        int64_t segmentFirstTimeUs;

        if (mMeta->findInt64("segmentFirstTimeUs", &segmentFirstTimeUs)) {

            segmentStartTimeUs += mTimeUs - segmentFirstTimeUs;

        }



        // adjust segment time by playlist age (for live streaming)

        int64_t playlistTimeUs;

        if (mMeta->findInt64("playlistTimeUs", &playlistTimeUs)) {

            int64_t playlistAgeUs = ALooper::GetNowUs() - playlistTimeUs;



            int64_t durationUs;

            CHECK(mMeta->findInt64("segmentDurationUs", &durationUs));

            segmentStartTimeUs += durationUs / 2;



            // round to nearest whole segment

            playlistAgeUs = (playlistAgeUs + durationUs / 2)

                    / durationUs * durationUs;



            segmentStartTimeUs -= playlistAgeUs;

            if (segmentStartTimeUs < 0) {

                segmentStartTimeUs = 0;

            }

        }

    }

    return segmentStartTimeUs;

media/libstagefright/httplive/LiveSession.cpp

+50 −8
Original line number Diff line number Diff line
@@ -67,7 +67,7 @@ struct LiveSession::BandwidthEstimator : public RefBase { 
    BandwidthEstimator();



    void addBandwidthMeasurement(size_t numBytes, int64_t delayUs);

    bool estimateBandwidth(int32_t *bandwidth);

    bool estimateBandwidth(int32_t *bandwidth, bool *isStable = NULL);



private:

    // Bandwidth estimation parameters
@@ -81,6 +81,9 @@ private: 


    Mutex mLock;

    List<BandwidthEntry> mBandwidthHistory;

    List<int32_t> mPrevEstimates;

    bool mHasNewSample;

    bool mIsStable;

    int64_t mTotalTransferTimeUs;

    size_t mTotalTransferBytes;
@@ -88,6 +91,8 @@ private: 
};



LiveSession::BandwidthEstimator::BandwidthEstimator() :

    mHasNewSample(false),

    mIsStable(true),

    mTotalTransferTimeUs(0),

    mTotalTransferBytes(0) {

}
@@ -102,6 +107,7 @@ void LiveSession::BandwidthEstimator::addBandwidthMeasurement( 
    mTotalTransferTimeUs += delayUs;

    mTotalTransferBytes += numBytes;

    mBandwidthHistory.push_back(entry);

    mHasNewSample = true;



    // trim old samples, keeping at least kMaxBandwidthHistoryItems samples,

    // and total transfer time at least kMaxBandwidthHistoryWindowUs.
@@ -116,14 +122,43 @@ void LiveSession::BandwidthEstimator::addBandwidthMeasurement( 
    }

}



bool LiveSession::BandwidthEstimator::estimateBandwidth(int32_t *bandwidthBps) {

bool LiveSession::BandwidthEstimator::estimateBandwidth(int32_t *bandwidthBps, bool *isStable) {

    AutoMutex autoLock(mLock);



    if (mBandwidthHistory.size() < 2) {

        return false;

    }



    if (!mHasNewSample) {

        *bandwidthBps = *(--mPrevEstimates.end());

        if (isStable) {

            *isStable = mIsStable;

        }

        return true;

    }



    *bandwidthBps = ((double)mTotalTransferBytes * 8E6 / mTotalTransferTimeUs);

    mPrevEstimates.push_back(*bandwidthBps);

    while (mPrevEstimates.size() > 3) {

        mPrevEstimates.erase(mPrevEstimates.begin());

    }

    mHasNewSample = false;



    int32_t minEstimate = -1, maxEstimate = -1;

    List<int32_t>::iterator it;

    for (it = mPrevEstimates.begin(); it != mPrevEstimates.end(); it++) {

        int32_t estimate = *it;

        if (minEstimate < 0 || minEstimate > estimate) {

            minEstimate = estimate;

        }

        if (maxEstimate < 0 || maxEstimate < estimate) {

            maxEstimate = estimate;

        }

    }

    mIsStable = (maxEstimate <= minEstimate * 4 / 3);

    if (isStable) {

       *isStable = mIsStable;

    }

    return true;

}
@@ -1930,7 +1965,7 @@ void LiveSession::onChangeConfiguration3(const sp<AMessage> &msg) { 
                fetcher->getFetcherID(),

                (long long)startTime.mTimeUs,

                (long long)mLastSeekTimeUs,

                (long long)startTime.getSegmentTimeUs(true /* midpoint */),

                (long long)startTime.getSegmentTimeUs(),

                seekMode);



        // Set the target segment start time to the middle point of the
@@ -1945,7 +1980,7 @@ void LiveSession::onChangeConfiguration3(const sp<AMessage> &msg) { 
                sources[kSubtitleIndex],

                getMetadataSource(sources, mNewStreamMask, switching),

                startTime.mTimeUs < 0 ? mLastSeekTimeUs : startTime.mTimeUs,

                startTime.getSegmentTimeUs(true /* midpoint */),

                startTime.getSegmentTimeUs(),

                startTime.mSeq,

                seekMode);

    }
@@ -2296,7 +2331,8 @@ bool LiveSession::switchBandwidthIfNeeded(bool bufferHigh, bool bufferLow) { 
    }



    int32_t bandwidthBps;

    if (mBandwidthEstimator->estimateBandwidth(&bandwidthBps)) {

    bool isStable;

    if (mBandwidthEstimator->estimateBandwidth(&bandwidthBps, &isStable)) {

        ALOGV("bandwidth estimated at %.2f kbps", bandwidthBps / 1024.0f);

        mLastBandwidthBps = bandwidthBps;

    } else {
@@ -2308,12 +2344,18 @@ bool LiveSession::switchBandwidthIfNeeded(bool bufferHigh, bool bufferLow) { 
    // canSwithDown and canSwitchUp can't both be true.

    // we only want to switch up when measured bw is 120% higher than current variant,

    // and we only want to switch down when measured bw is below current variant.

    bool canSwithDown = bufferLow

    bool canSwitchDown = bufferLow

            && (bandwidthBps < (int32_t)curBandwidth);

    bool canSwitchUp = bufferHigh

            && (bandwidthBps > (int32_t)curBandwidth * 12 / 10);



    if (canSwithDown || canSwitchUp) {

    if (canSwitchDown || canSwitchUp) {

        // bandwidth estimating has some delay, if we have to downswitch when

        // it hasn't stabilized, be very conservative on bandwidth.

        if (!isStable && canSwitchDown) {

            bandwidthBps /= 2;

        }



        ssize_t bandwidthIndex = getBandwidthIndex(bandwidthBps);



        // it's possible that we're checking for canSwitchUp case, but the returned
@@ -2321,7 +2363,7 @@ bool LiveSession::switchBandwidthIfNeeded(bool bufferHigh, bool bufferLow) { 
        // of measured bw. In that case we don't want to do anything, since we have

        // both enough buffer and enough bw.

        if ((canSwitchUp && bandwidthIndex > mCurBandwidthIndex)

         || (canSwithDown && bandwidthIndex < mCurBandwidthIndex)) {

         || (canSwitchDown && bandwidthIndex < mCurBandwidthIndex)) {

            // if not yet prepared, just restart again with new bw index.

            // this is faster and playback experience is cleaner.

            changeConfiguration(

media/libstagefright/httplive/M3UParser.cpp

+32 −5
Original line number Diff line number Diff line
@@ -250,6 +250,9 @@ M3UParser::M3UParser( 
      mIsVariantPlaylist(false),

      mIsComplete(false),

      mIsEvent(false),

      mFirstSeqNumber(-1),

      mLastSeqNumber(-1),

      mTargetDurationUs(-1ll),

      mDiscontinuitySeq(0),

      mDiscontinuityCount(0),

      mSelectedIndex(-1) {
@@ -283,6 +286,19 @@ size_t M3UParser::getDiscontinuitySeq() const { 
    return mDiscontinuitySeq;

}



int64_t M3UParser::getTargetDuration() const {

    return mTargetDurationUs;

}



int32_t M3UParser::getFirstSeqNumber() const {

    return mFirstSeqNumber;

}



void M3UParser::getSeqNumberRange(int32_t *firstSeq, int32_t *lastSeq) const {

    *firstSeq = mFirstSeqNumber;

    *lastSeq = mLastSeqNumber;

}



sp<AMessage> M3UParser::meta() {

    return mMeta;

}
@@ -664,12 +680,23 @@ status_t M3UParser::parse(const void *_data, size_t size) { 
    }



    // error checking of all fields that's required to appear once

    // (currently only checking "target-duration")

    // (currently only checking "target-duration"), and

    // initialization of playlist properties (eg. mTargetDurationUs)

    if (!mIsVariantPlaylist) {

        int32_t targetDurationSecs;

    if (!mIsVariantPlaylist && (mMeta == NULL || !mMeta->findInt32(

            "target-duration", &targetDurationSecs))) {

        if (mMeta == NULL || !mMeta->findInt32(

                "target-duration", &targetDurationSecs)) {

            ALOGE("Media playlist missing #EXT-X-TARGETDURATION");

            return ERROR_MALFORMED;

        }

        mTargetDurationUs = targetDurationSecs * 1000000ll;



        mFirstSeqNumber = 0;

        if (mMeta != NULL) {

            mMeta->findInt32("media-sequence", &mFirstSeqNumber);

        }

        mLastSeqNumber = mFirstSeqNumber + mItems.size() - 1;

    }



    return OK;

}

media/libstagefright/httplive/M3UParser.h

+6 −0
Original line number Diff line number Diff line
@@ -36,6 +36,9 @@ struct M3UParser : public RefBase { 
    bool isComplete() const;

    bool isEvent() const;

    size_t getDiscontinuitySeq() const;

    int64_t getTargetDuration() const;

    int32_t getFirstSeqNumber() const;

    void getSeqNumberRange(int32_t *firstSeq, int32_t *lastSeq) const;



    sp<AMessage> meta();
@@ -70,6 +73,9 @@ private: 
    bool mIsVariantPlaylist;

    bool mIsComplete;

    bool mIsEvent;

    int32_t mFirstSeqNumber;

    int32_t mLastSeqNumber;

    int64_t mTargetDurationUs;

    size_t mDiscontinuitySeq;

    int32_t mDiscontinuityCount;