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VPAAMP-684:Tech Fault error leads to Blue Screen when rewinding from … #1693

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35 changes: 29 additions & 6 deletions MediaStreamContext.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -73,8 +73,13 @@ bool MediaStreamContext::CacheFragment(std::string fragmentUrl, unsigned int cur
mStagingFragment.Clear();
CachedFragment *cachedFragment = &mStagingFragment;
BitsPerSecond bitrate = 0;
BitsPerSecond expectedBandwidth = fragmentDescriptor.Bandwidth;
double downloadTimeS = 0;
AampMediaType actualType = (AampMediaType)(initSegment ? (eMEDIATYPE_INIT_VIDEO + mediaType) : mediaType); // Need to revisit the logic
if (mActiveDownloadInfo && mActiveDownloadInfo->bandwidth > 0)
{
Comment on lines +76 to +80
expectedBandwidth = mActiveDownloadInfo->bandwidth;
}

PopulateCommonMetadata(cachedFragment, fragmentUrl, actualType, 0, initSegment, discontinuity);
cachedFragment->timeScale = fragmentDescriptor.TimeScale;
Expand Down Expand Up @@ -109,7 +114,11 @@ bool MediaStreamContext::CacheFragment(std::string fragmentUrl, unsigned int cur
bool bReadfromcache = false;
if (initSegment)
{
ret = bReadfromcache = aamp->getAampCacheHandler()->RetrieveFromInitFragmentCache(fragmentUrl,cachedFragment->fragment,effectiveUrl);
auto *cacheHandler = aamp->getAampCacheHandler();
if (cacheHandler)
{
ret = bReadfromcache = cacheHandler->RetrieveFromInitFragmentCache(fragmentUrl, cachedFragment->fragment, effectiveUrl);
}
}
if (!bReadfromcache)
{
Expand All @@ -131,7 +140,11 @@ bool MediaStreamContext::CacheFragment(std::string fragmentUrl, unsigned int cur
ret = aamp->GetFile(fragmentUrl, actualType, mTempFragment, effectiveUrl, httpErrorCode, &downloadTimeS, range, curlInstance, true/*resetBuffer*/, &bitrate, &iFogError, fragmentDurationS, bucketType, maxInitDownloadTimeMS);
if (initSegment && ret)
{
aamp->getAampCacheHandler()->InsertToInitFragCache(fragmentUrl, mTempFragment, effectiveUrl, actualType);
auto *cacheHandler = aamp->getAampCacheHandler();
if (cacheHandler)
{
cacheHandler->InsertToInitFragCache(fragmentUrl, mTempFragment, effectiveUrl, actualType);
}
}
if (ret)
{
Expand Down Expand Up @@ -181,10 +194,10 @@ bool MediaStreamContext::CacheFragment(std::string fragmentUrl, unsigned int cur
}

mCheckForRampdown = false;
if (ret && (bitrate > 0 && bitrate != fragmentDescriptor.Bandwidth))
if (ret && (bitrate > 0 && bitrate != expectedBandwidth))
{
AAMPLOG_INFO("Bitrate changed from %" BITSPERSECOND_FORMAT " to %" BITSPERSECOND_FORMAT "",
fragmentDescriptor.Bandwidth, bitrate);
expectedBandwidth, bitrate);
fragmentDescriptor.Bandwidth = (uint32_t)bitrate;
context->SetTsbBandwidth(bitrate);
context->mUpdateReason = true;
Expand Down Expand Up @@ -1047,10 +1060,21 @@ bool MediaStreamContext::DownloadFragment(DownloadInfoPtr dlInfo)
URIInfo uriInfo;
if (dlInfo->uriList.size() > 0)
{
// Asses the current bandwidth and get the appropriate URIInfo from the map with resolved URLs
// Assess the current bandwidth and get the appropriate URIInfo from the map with resolved URLs.
if (dlInfo->uriList.find(fragmentDescriptor.Bandwidth) != dlInfo->uriList.end())
{
uriInfo = dlInfo->uriList[fragmentDescriptor.Bandwidth];
// Sync dlInfo->bandwidth to the selected bandwidth to avoid mismatch in downstream comparisons
// (e.g. bitrate check in CacheFragment) when a period/ad-state change updated fragmentDescriptor.Bandwidth.
if (dlInfo->bandwidth != fragmentDescriptor.Bandwidth)
{
dlInfo->bandwidth = fragmentDescriptor.Bandwidth;
}
Comment on lines +1069 to +1072
}
// Fallback to job submission bandwidth if descriptor bandwidth is not present in the map.
else if ((dlInfo->bandwidth > 0) && (dlInfo->uriList.find(dlInfo->bandwidth) != dlInfo->uriList.end()))
{
uriInfo = dlInfo->uriList[dlInfo->bandwidth];
}
if (uriInfo.url.empty() && dlInfo->uriList.size() > 0)
{
Expand Down Expand Up @@ -1206,6 +1230,5 @@ bool MediaStreamContext::DownloadFragment(DownloadInfoPtr dlInfo)
retval = CacheFragment(dlInfo->url, dlInfo->curlInstance, dlInfo->pts, dlInfo->fragmentDurationSec, dlInfo->range.c_str(), dlInfo->isInitSegment, dlInfo->isDiscontinuity, dlInfo->isPlayingAd, dlInfo->timeScale);
}
}

return retval;
}
168 changes: 168 additions & 0 deletions test/utests/tests/CacheFragmentTests/CacheFragmentTests.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,7 @@ using ::testing::StrictMock;
using ::testing::SetArgReferee;
using ::testing::AtLeast;
using ::testing::DoAll;
using ::testing::SetArgPointee;

AampConfig *gpGlobalConfig{nullptr};
struct TestParams
Expand Down Expand Up @@ -388,4 +389,171 @@ INSTANTIATE_TEST_SUITE_P(
::testing::ValuesIn(testCases)
);

/**
* @brief Verifies that an init segment download succeeds when fragmentDescriptor.Bandwidth
* has advanced to the ad period's bandwidth while a source-content init segment job
* is still in-flight.
*
* The fix introduces expectedBandwidth, overridden with mActiveDownloadInfo->bandwidth
* (captured at job-submission time). When FOG returns the correct content bitrate, it
* matches expectedBandwidth and no false rampdown fires.
*/
TEST_F(MediaStreamContextTest, CacheFragment_InitSegment_FogBitrateMismatch_ReturnsSuccess)
{
// --- Arrange ---
static constexpr BitsPerSecond kJobBandwidth = 2000000; // BW at job-submission (source content)
static constexpr BitsPerSecond kAdPeriodBandwidth = 5000000; // ad period's bandwidth — fragmentDescriptor advances to this during the period transition

// Create the MediaStreamContext (TEST_F does not call Initialize())
mMediaStreamContext = new MediaStreamContext(eTRACK_VIDEO, mStreamAbstractionAAMP_MPD, mPrivateInstanceAAMP, "SAMPLETEXT");

// Simulate the race: period transitioned to the ad, updating fragmentDescriptor.Bandwidth to the ad period's BW
mMediaStreamContext->fragmentDescriptor.Bandwidth = kAdPeriodBandwidth;

URIInfo uriInfo;
uriInfo.url = "http://example.com/init.mp4";
URLBitrateMap urlList = { { kJobBandwidth, uriInfo } };

// dlInfo->bandwidth = job-submission BW (2Mbps) — this overrides expectedBandwidth
mMediaStreamContext->mActiveDownloadInfo = std::make_shared<DownloadInfo>(
eMEDIATYPE_VIDEO, eCURLINSTANCE_VIDEO,
10.0, 0.0, "", -1, 0,
/*isInitSegment=*/true, false, false, false,
0.0, 0, 1, kJobBandwidth, AampTime{}, urlList);

// FOG serves and reports the correct 2Mbps content bandwidth
EXPECT_CALL(*g_mockPrivateInstanceAAMP, GetFile(_, _, _, _, _, _, _, _, _, _, _, _, _, _))
.WillOnce(DoAll(SetArgPointee<9>(kJobBandwidth), Return(true)));
EXPECT_CALL(*g_mockPrivateInstanceAAMP, GetTSBSessionManager())
.WillRepeatedly(Return(nullptr));
EXPECT_CALL(*g_mockPrivateInstanceAAMP, GetLLDashChunkMode())
.WillRepeatedly(Return(false));

// --- Act ---
bool result = mMediaStreamContext->CacheFragment(
uriInfo.url, 0, 10.0, 0.0, nullptr, /*initSegment=*/true, false, false, 0);

// --- Assert ---
// Init segment must succeed.
// expectedBandwidth = dlInfo->bandwidth (2Mbps) == bitrate from FOG (2Mbps) → no rampdown.
EXPECT_TRUE(result) << "Init segment must succeed when expectedBandwidth fix prevents false rampdown";

// fragmentDescriptor.Bandwidth must not be touched — rampdown never fired.
EXPECT_EQ(mMediaStreamContext->fragmentDescriptor.Bandwidth, static_cast<uint32_t>(kAdPeriodBandwidth))
<< "fragmentDescriptor.Bandwidth must not be updated when rampdown does not fire";

// No bytes stashed for reschedule (download succeeded).
EXPECT_TRUE(mMediaStreamContext->mDownloadedFragment.empty())
<< "mDownloadedFragment must be empty when init segment succeeds";
}

/**
* @brief Verifies that rampdown still fires for media segments when FOG reports a
* genuinely different bitrate — ensuring the expectedBandwidth fix does not
* suppress legitimate ABR rampdown for media fragments.
*/
TEST_F(MediaStreamContextTest, CacheFragment_MediaSegment_FogBitrateMismatch_RampdownTriggered)
{
// --- Arrange ---
static constexpr BitsPerSecond kJobBandwidth = 2000000;
static constexpr BitsPerSecond kFogReportedBitrate = 5000000;

// Create the MediaStreamContext (TEST_F does not call Initialize())
mMediaStreamContext = new MediaStreamContext(eTRACK_VIDEO, mStreamAbstractionAAMP_MPD, mPrivateInstanceAAMP, "SAMPLETEXT");

mMediaStreamContext->fragmentDescriptor.Bandwidth = kJobBandwidth;

URIInfo uriInfo;
uriInfo.url = "http://example.com/segment.mp4";
URLBitrateMap urlList = { { kJobBandwidth, uriInfo } };

mMediaStreamContext->mActiveDownloadInfo = std::make_shared<DownloadInfo>(
eMEDIATYPE_VIDEO, eCURLINSTANCE_VIDEO,
10.0, 2.0, "", -1, 0,
/*isInitSegment=*/false, false, false, false,
0.0, 0, 1, kJobBandwidth, AampTime{}, urlList);

// FOG reports mismatched bitrate for a media segment → rampdown must fire.
static const std::vector<uint8_t> kSegmentBytes{0xAA, 0xBB, 0xCC, 0xDD};
EXPECT_CALL(*g_mockPrivateInstanceAAMP, GetFile(_, _, _, _, _, _, _, _, _, _, _, _, _, _))
.WillOnce(DoAll(SetArgReferee<2>(kSegmentBytes), SetArgPointee<9>(kFogReportedBitrate), Return(true)));
EXPECT_CALL(*g_mockPrivateInstanceAAMP, GetTSBSessionManager())
.WillRepeatedly(Return(nullptr));
EXPECT_CALL(*g_mockPrivateInstanceAAMP, GetLLDashChunkMode())
.WillRepeatedly(Return(false));

// --- Act ---
bool result = mMediaStreamContext->CacheFragment(
uriInfo.url, 0, 10.0, 2.0, nullptr, /*initSegment=*/false, false, false, 0);

// --- Assert ---
// Rampdown must still trigger for media segments (existing behavior preserved).
EXPECT_FALSE(result) << "Media segment rampdown must trigger on FOG bitrate mismatch";

// Descriptor updated to FOG-reported bitrate for the next download attempt.
EXPECT_EQ(mMediaStreamContext->fragmentDescriptor.Bandwidth, static_cast<uint32_t>(kFogReportedBitrate))
<< "fragmentDescriptor.Bandwidth must be updated to FOG-reported bitrate on rampdown";

// Downloaded bytes saved in mDownloadedFragment for the reschedule/reuse path.
EXPECT_FALSE(mMediaStreamContext->mDownloadedFragment.empty())
<< "mDownloadedFragment must hold the downloaded bytes for reschedule reuse";
}

/**
* @brief Verifies that rampdown fires for init segments when FOG reports a genuinely
* different bitrate — confirming the rampdown check applies equally to init
* segments, not only media segments.
*
* Unlike the period-transition race scenario, here fragmentDescriptor.Bandwidth equals
* the job-submission bandwidth. FOG returning a different bitrate is a genuine mismatch
* and rampdown must trigger.
*/
TEST_F(MediaStreamContextTest, CacheFragment_InitSegment_GenuineFogBitrateMismatch_RampdownTriggered)
{
// --- Arrange ---
static constexpr BitsPerSecond kJobBandwidth = 2000000;
static constexpr BitsPerSecond kFogReportedBitrate = 5000000;

// Create the MediaStreamContext (TEST_F does not call Initialize())
mMediaStreamContext = new MediaStreamContext(eTRACK_VIDEO, mStreamAbstractionAAMP_MPD, mPrivateInstanceAAMP, "SAMPLETEXT");

// No period transition: descriptor BW matches the job-submission BW
mMediaStreamContext->fragmentDescriptor.Bandwidth = kJobBandwidth;

URIInfo uriInfo;
uriInfo.url = "http://example.com/init.mp4";
URLBitrateMap urlList = { { kJobBandwidth, uriInfo } };

mMediaStreamContext->mActiveDownloadInfo = std::make_shared<DownloadInfo>(
eMEDIATYPE_VIDEO, eCURLINSTANCE_VIDEO,
10.0, 0.0, "", -1, 0,
/*isInitSegment=*/true, false, false, false,
0.0, 0, 1, kJobBandwidth, AampTime{}, urlList);

// FOG reports a genuinely different bitrate for the init segment → rampdown must fire.
static const std::vector<uint8_t> kInitSegmentBytes{0x00, 0x00, 0x00, 0x20};
EXPECT_CALL(*g_mockPrivateInstanceAAMP, GetFile(_, _, _, _, _, _, _, _, _, _, _, _, _, _))
.WillOnce(DoAll(SetArgReferee<2>(kInitSegmentBytes), SetArgPointee<9>(kFogReportedBitrate), Return(true)));
EXPECT_CALL(*g_mockPrivateInstanceAAMP, GetTSBSessionManager())
.WillRepeatedly(Return(nullptr));
EXPECT_CALL(*g_mockPrivateInstanceAAMP, GetLLDashChunkMode())
.WillRepeatedly(Return(false));

// --- Act ---
bool result = mMediaStreamContext->CacheFragment(
uriInfo.url, 0, 10.0, 0.0, nullptr, /*initSegment=*/true, false, false, 0);

// --- Assert ---
// Rampdown must trigger for init segments on genuine FOG bitrate mismatch.
EXPECT_FALSE(result) << "Init segment rampdown must trigger on genuine FOG bitrate mismatch";

// Descriptor updated to FOG-reported bitrate for the next download attempt.
EXPECT_EQ(mMediaStreamContext->fragmentDescriptor.Bandwidth, static_cast<uint32_t>(kFogReportedBitrate))
<< "fragmentDescriptor.Bandwidth must be updated to FOG-reported bitrate on rampdown";

// Downloaded bytes saved in mDownloadedFragment for the reschedule/reuse path.
EXPECT_FALSE(mMediaStreamContext->mDownloadedFragment.empty())
<< "mDownloadedFragment must hold the downloaded bytes for reschedule reuse";
}


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