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author | Chong Zhang <chz@google.com> | 2015-03-17 14:10:07 -0700 |
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committer | Chong Zhang <chz@google.com> | 2015-03-19 12:38:37 -0700 |
commit | 538b6d22a3578c0201d48f8548289aa254d81484 (patch) | |
tree | 626c785a041cdf9c268a874f07e478c3f2d023c2 /media/libstagefright/httplive/LiveSession.cpp | |
parent | 1c15c670928bab5eef6b1a06cf49378abb1e70bf (diff) | |
download | frameworks_av-538b6d22a3578c0201d48f8548289aa254d81484.zip frameworks_av-538b6d22a3578c0201d48f8548289aa254d81484.tar.gz frameworks_av-538b6d22a3578c0201d48f8548289aa254d81484.tar.bz2 |
HLS: bandwidth estimator changes
- separate bandwidth estimator from HTTPBase, so that we have
better control on which samples to use, it also allows bandiwdth
history across multiple HTTPBase objects (which we'll use later).
- use min buffer duration among the streams to decide whether to
download next segment.
- maintain constant buffer level, time next download to happen
when buffer just goes below kMinBufferedDurationUs.
bug: 19567254
Change-Id: I5c481ad1f7ff3f084d57ec68856e12ae6b40ce41
Diffstat (limited to 'media/libstagefright/httplive/LiveSession.cpp')
-rw-r--r-- | media/libstagefright/httplive/LiveSession.cpp | 147 |
1 files changed, 109 insertions, 38 deletions
diff --git a/media/libstagefright/httplive/LiveSession.cpp b/media/libstagefright/httplive/LiveSession.cpp index a94754b..f5328a6 100644 --- a/media/libstagefright/httplive/LiveSession.cpp +++ b/media/libstagefright/httplive/LiveSession.cpp @@ -50,13 +50,75 @@ namespace android { // static -// Number of recently-read bytes to use for bandwidth estimation -const size_t LiveSession::kBandwidthHistoryBytes = 200 * 1024; // High water mark to start up switch or report prepared) const int64_t LiveSession::kHighWaterMark = 8000000ll; const int64_t LiveSession::kMidWaterMark = 5000000ll; const int64_t LiveSession::kLowWaterMark = 3000000ll; +struct LiveSession::BandwidthEstimator : public RefBase { + BandwidthEstimator(); + + void addBandwidthMeasurement(size_t numBytes, int64_t delayUs); + bool estimateBandwidth(int32_t *bandwidth); + +private: + // Bandwidth estimation parameters + static const int32_t kMaxBandwidthHistoryItems = 20; + static const int64_t kMaxBandwidthHistoryWindowUs = 3000000ll; // 3 sec + + struct BandwidthEntry { + int64_t mDelayUs; + size_t mNumBytes; + }; + + Mutex mLock; + List<BandwidthEntry> mBandwidthHistory; + int64_t mTotalTransferTimeUs; + size_t mTotalTransferBytes; + + DISALLOW_EVIL_CONSTRUCTORS(BandwidthEstimator); +}; + +LiveSession::BandwidthEstimator::BandwidthEstimator() : + mTotalTransferTimeUs(0), + mTotalTransferBytes(0) { +} + +void LiveSession::BandwidthEstimator::addBandwidthMeasurement( + size_t numBytes, int64_t delayUs) { + AutoMutex autoLock(mLock); + + BandwidthEntry entry; + entry.mDelayUs = delayUs; + entry.mNumBytes = numBytes; + mTotalTransferTimeUs += delayUs; + mTotalTransferBytes += numBytes; + mBandwidthHistory.push_back(entry); + + // trim old samples, keeping at least kMaxBandwidthHistoryItems samples, + // and total transfer time at least kMaxBandwidthHistoryWindowUs. + while (mBandwidthHistory.size() > kMaxBandwidthHistoryItems) { + List<BandwidthEntry>::iterator it = mBandwidthHistory.begin(); + if (mTotalTransferTimeUs - it->mDelayUs < kMaxBandwidthHistoryWindowUs) { + break; + } + mTotalTransferTimeUs -= it->mDelayUs; + mTotalTransferBytes -= it->mNumBytes; + mBandwidthHistory.erase(mBandwidthHistory.begin()); + } +} + +bool LiveSession::BandwidthEstimator::estimateBandwidth(int32_t *bandwidthBps) { + AutoMutex autoLock(mLock); + + if (mBandwidthHistory.size() < 2) { + return false; + } + + *bandwidthBps = ((double)mTotalTransferBytes * 8E6 / mTotalTransferTimeUs); + return true; +} + LiveSession::LiveSession( const sp<AMessage> ¬ify, uint32_t flags, const sp<IMediaHTTPService> &httpService) @@ -66,10 +128,10 @@ LiveSession::LiveSession( mInPreparationPhase(true), mHTTPDataSource(new MediaHTTP(mHTTPService->makeHTTPConnection())), mCurBandwidthIndex(-1), + mBandwidthEstimator(new BandwidthEstimator()), mStreamMask(0), mNewStreamMask(0), mSwapMask(0), - mCheckBandwidthGeneration(0), mSwitchGeneration(0), mSubtitleGeneration(0), mLastDequeuedTimeUs(0ll), @@ -89,13 +151,6 @@ LiveSession::LiveSession( mPacketSources.add(indexToType(i), new AnotherPacketSource(NULL /* meta */)); mPacketSources2.add(indexToType(i), new AnotherPacketSource(NULL /* meta */)); } - - size_t numHistoryItems = kBandwidthHistoryBytes / - PlaylistFetcher::kDownloadBlockSize + 1; - if (numHistoryItems < 5) { - numHistoryItems = 5; - } - mHTTPDataSource->setBandwidthHistorySize(numHistoryItems); } LiveSession::~LiveSession() { @@ -948,8 +1003,15 @@ static double uniformRand() { } #endif -size_t LiveSession::getBandwidthIndex() { - if (mBandwidthItems.size() == 0) { +void LiveSession::addBandwidthMeasurement(size_t numBytes, int64_t delayUs) { + mBandwidthEstimator->addBandwidthMeasurement(numBytes, delayUs); +} + +size_t LiveSession::getBandwidthIndex(int32_t bandwidthBps) { + if (mBandwidthItems.size() < 2) { + // shouldn't be here if we only have 1 bandwidth, check + // logic to get rid of redundant bandwidth polling + ALOGW("getBandwidthIndex() called for single bandwidth playlist!"); return 0; } @@ -967,15 +1029,6 @@ size_t LiveSession::getBandwidthIndex() { } if (index < 0) { - int32_t bandwidthBps; - if (mHTTPDataSource != NULL - && mHTTPDataSource->estimateBandwidth(&bandwidthBps)) { - ALOGV("bandwidth estimated at %.2f kbps", bandwidthBps / 1024.0f); - } else { - ALOGV("no bandwidth estimate."); - return 0; // Pick the lowest bandwidth stream by default. - } - char value[PROPERTY_VALUE_MAX]; if (property_get("media.httplive.max-bw", value, NULL)) { char *end; @@ -992,15 +1045,9 @@ size_t LiveSession::getBandwidthIndex() { index = mBandwidthItems.size() - 1; while (index > 0) { - // consider only 80% of the available bandwidth, but if we are switching up, - // be even more conservative (70%) to avoid overestimating and immediately - // switching back. - size_t adjustedBandwidthBps = bandwidthBps; - if (index > mCurBandwidthIndex) { - adjustedBandwidthBps = adjustedBandwidthBps * 7 / 10; - } else { - adjustedBandwidthBps = adjustedBandwidthBps * 8 / 10; - } + // be conservative (70%) to avoid overestimating and immediately + // switching down again. + size_t adjustedBandwidthBps = bandwidthBps * 7 / 10; if (mBandwidthItems.itemAt(index).mBandwidth <= adjustedBandwidthBps) { break; } @@ -1577,9 +1624,9 @@ void LiveSession::cancelPollBuffering() { void LiveSession::onPollBuffering() { ALOGV("onPollBuffering: mSwitchInProgress %d, mReconfigurationInProgress %d, " - "mInPreparationPhase %d, mStreamMask 0x%x", + "mInPreparationPhase %d, mCurBandwidthIndex %d, mStreamMask 0x%x", mSwitchInProgress, mReconfigurationInProgress, - mInPreparationPhase, mStreamMask); + mInPreparationPhase, mCurBandwidthIndex, mStreamMask); bool low, mid, high; if (checkBuffering(low, mid, high)) { @@ -1588,8 +1635,8 @@ void LiveSession::onPollBuffering() { } // don't switch before we report prepared - if (!mInPreparationPhase && (low || high)) { - switchBandwidthIfNeeded(high); + if (!mInPreparationPhase) { + switchBandwidthIfNeeded(high, !mid); } } @@ -1704,11 +1751,35 @@ bool LiveSession::checkBuffering(bool &low, bool &mid, bool &high) { return false; } -void LiveSession::switchBandwidthIfNeeded(bool canSwitchUp) { - ssize_t bandwidthIndex = getBandwidthIndex(); +void LiveSession::switchBandwidthIfNeeded(bool bufferHigh, bool bufferLow) { + // no need to check bandwidth if we only have 1 bandwidth settings + if (mBandwidthItems.size() < 2) { + return; + } + + int32_t bandwidthBps; + if (mBandwidthEstimator->estimateBandwidth(&bandwidthBps)) { + ALOGV("bandwidth estimated at %.2f kbps", bandwidthBps / 1024.0f); + } else { + ALOGV("no bandwidth estimate."); + return; + } + + int32_t curBandwidth = mBandwidthItems.itemAt(mCurBandwidthIndex).mBandwidth; + bool bandwidthLow = bandwidthBps < (int32_t)curBandwidth * 8 / 10; + bool bandwidthHigh = bandwidthBps > (int32_t)curBandwidth * 12 / 10; + + if ((bufferHigh && bandwidthHigh) || (bufferLow && bandwidthLow)) { + ssize_t bandwidthIndex = getBandwidthIndex(bandwidthBps); + + if (bandwidthIndex == mCurBandwidthIndex + || (bufferHigh && bandwidthIndex < mCurBandwidthIndex) + || (bufferLow && bandwidthIndex > mCurBandwidthIndex)) { + return; + } - if ((canSwitchUp && bandwidthIndex > mCurBandwidthIndex) - || (!canSwitchUp && bandwidthIndex < mCurBandwidthIndex)) { + ALOGI("#### Initiate Bandwidth Switch: %d => %d", + mCurBandwidthIndex, bandwidthIndex); changeConfiguration(-1, bandwidthIndex, false); } } |