VPAAMP-292: LLD Target Latency not Increasing on Underflow

[srikanthreddybijjam-comcast]

Reason for change: Added buffer check for audio along with video
Test Procedure: Refer the ticket VPAAMP-292
Priority: P1

[Copilot]

Pull request overview

Updates latency-monitor buffer accounting so underflow/low-buffer on audio can drive adaptive target-latency increases (VPAAMP-292), rather than relying on video-only buffered duration.

Changes:

• Introduce GetMinAVBufferedDuration{,Secs}() to report min(audio, video) buffered duration for latency-monitor decisions.
• Switch latency-monitor polling/wakeup paths to use the new min A/V buffered duration.
• Update/add L1 tests and fakes/mocks to exercise and support the new audio-buffer behavior.

Reviewed changes

Copilot reviewed 11 out of 11 changed files in this pull request and generated 4 comments.

Show a summary per file

File	Description
streamabstraction.cpp	Adds StreamAbstractionAAMP::GetMinAVBufferedDuration() implementation (min A/V buffer).
StreamAbstractionAAMP.h	Declares GetMinAVBufferedDuration() API for stream abstraction.
priv_aamp.cpp	Implements PrivateInstanceAAMP::GetMinAVBufferedDurationSecs() with try_to_lock sentinel behavior.
priv_aamp.h	Declares GetMinAVBufferedDurationSecs() for latency-monitor consumption.
AampLatencyMonitor.cpp	Uses GetMinAVBufferedDurationSecs() for polling and sentinel handling.
MediaStreamContext.cpp	Notifies latency monitor using min A/V buffer instead of video-only buffer.
test/utests/mocks/MockPrivateInstanceAAMP.h	Extends mock interface with GetMinAVBufferedDurationSecs().
test/utests/fakes/FakePrivateInstanceAAMP.cpp	Adds fake delegation for GetMinAVBufferedDurationSecs() to the mock.
test/utests/fakes/FakeStreamAbstractionAamp.cpp	Adds stub for GetMinAVBufferedDuration() in the fake abstraction.
test/utests/tests/MediaStreamContextTests/FragmentDownloadTests.cpp	Updates expectations to the new buffer-duration method.
test/utests/tests/AampLatencyMonitorTests/AampLatencyMonitorTestCases.cpp	Updates existing tests and adds new cases validating audio-buffer-driven shifting and rate-correction suppression.

[Copilot]

Pull request overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

Suppressed comments (6)

MediaStreamContext.cpp:762

• Same issue as the earlier call site: taking std::min(video,audio) makes bufferMs negative when one track is unavailable (-1.0), preventing early notification even if the other track has a valid buffered duration. Compute min over valid (>= 0) durations instead.

			const AampAVBufferDuration avBuf = aamp->GetMinAVBufferedDurationSecs();
			const double bufferMs = std::min(avBuf.videoDurationSecs, avBuf.audioDurationSecs) * 1000.0;

test/utests/tests/MediaStreamContextTests/FragmentDownloadTests.cpp:79

• The comment says GetMinAVBufferedDurationSecs() is called for every video-track and audio-track fragment, but MediaStreamContext calls it only inside eTRACK_VIDEO branches. This comment is misleading for future test maintenance.

		// GetMinAVBufferedDurationSecs() is called for every video-track and audio-track fragment via

priv_aamp.cpp:15106

• Doxygen tag should be @return (not @returns) for consistency and correct extraction.

/**
 * @brief Get audio and video buffered durations for the latency monitor.
 * @returns buffer values in seconds
 */

AampLatencyMonitor.cpp:289

• bufferMs is computed as min(video,audio). However GetBuffered*DurationSec() can legitimately return -1.0 for a missing/disabled track (not only lock contention), which makes bufferMs negative and causes the latency poll to be skipped even when the other track has a valid buffered duration (e.g., audio-only or video-only playback). Consider ignoring negative per-track values and only treating the poll as unavailable when both are negative.

		const AampAVBufferDuration avBuf = mAamp->GetMinAVBufferedDurationSecs();
		const double bufferMs   = std::min(avBuf.videoDurationSecs, avBuf.audioDurationSecs) * 1000.0;

		// A negative bufferMs is the sentinel returned by GetMinAVBufferedDurationSecs()
		// when mStreamLock could not be acquired (std::try_to_lock contention).

MediaStreamContext.cpp:250

• This uses std::min(video,audio) directly, so if either track reports a negative sentinel (e.g., missing/disabled track), bufferMs becomes negative and the latency monitor won't be notified even though the other track may have valid buffered duration. Compute the minimum over valid (>= 0) durations instead.

This issue also appears on line 761 of the same file.

						const AampAVBufferDuration avBuf = aamp->GetMinAVBufferedDurationSecs();
						const double bufferMs = std::min(avBuf.videoDurationSecs, avBuf.audioDurationSecs) * 1000.0;
						if (bufferMs >= 0.0)

priv_aamp.h:4082

• The name GetMinAVBufferedDurationSecs suggests it returns a single minimum duration, but it actually returns both A/V durations in a struct (callers then compute the min). Consider renaming to reflect the return type (e.g., GetAVBufferedDurationSecs / GetAVBufferedDurationsSecs) to reduce API ambiguity.

	/**
	 * @fn GetMinAVBufferedDurationSecs
	 * @brief Get audio and video buffered durations for use by the latency monitor.
	 * @return AampAVBufferDuration containing both audio and video buffered durations in seconds.
	 */
	AampAVBufferDuration GetMinAVBufferedDurationSecs();