Camera: Handle deviation between frame duration and vsync intervals
When camera frame duration deviates from display vsync interval, the
current approach doesn't work because it favors delaying the frames to
latch onto next VSYNC interval.
We cannot compensate such delay by pulling in and latching onto an
ealier VSYNC signal. That will result in periods where frames are
displayed at 16ms, 50ms, 16ms, 50ms intervals for 30fps case.
The solution is to use different methods for different cases:
1. If the frame duration is multiples of VSYNC intervals, use existing
approach.
2. Otherwise, simply use the earlist expected presentation time in the
VSYNC timeline.
Test: Run camera at lower FPS (24) and observe trace
Test: No regression for fixed 30fps or 60fps use cases
Test: Vendor verifies 24/30/60 fps display rate on different SoC chips
Test: PerformanceTest#testSurfaceViewJitterReduction
Bug: 236389092
Change-Id: I5408192550a1e09b18c4c0aa255a7687bf5dd829
diff --git a/services/camera/libcameraservice/device3/Camera3OutputStream.cpp b/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
index da1cf09..7e2ea49 100644
--- a/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
+++ b/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
@@ -18,6 +18,7 @@
#define ATRACE_TAG ATRACE_TAG_CAMERA
//#define LOG_NDEBUG 0
+#include <algorithm>
#include <ctime>
#include <fstream>
@@ -1392,14 +1393,30 @@
const VsyncEventData& vsyncEventData = parcelableVsyncEventData.vsync;
nsecs_t currentTime = systemTime();
- // Reset capture to present time offset if more than 1 second
- // between frames.
- if (t - mLastCaptureTime > kSpacingResetIntervalNs) {
+ // Reset capture to present time offset if:
+ // - More than 1 second between frames.
+ // - The frame duration deviates from multiples of vsync frame intervals.
+ nsecs_t captureInterval = t - mLastCaptureTime;
+ float captureToVsyncIntervalRatio = 1.0f * captureInterval / vsyncEventData.frameInterval;
+ float ratioDeviation = std::fabs(
+ captureToVsyncIntervalRatio - std::roundf(captureToVsyncIntervalRatio));
+ if (captureInterval > kSpacingResetIntervalNs ||
+ ratioDeviation >= kMaxIntervalRatioDeviation) {
+ nsecs_t minPresentT = mLastPresentTime + vsyncEventData.frameInterval / 2;
for (size_t i = 0; i < VsyncEventData::kFrameTimelinesLength; i++) {
- if (vsyncEventData.frameTimelines[i].deadlineTimestamp >= currentTime) {
- mCaptureToPresentOffset =
- vsyncEventData.frameTimelines[i].expectedPresentationTime - t;
- break;
+ const auto& timeline = vsyncEventData.frameTimelines[i];
+ if (timeline.deadlineTimestamp >= currentTime &&
+ timeline.expectedPresentationTime > minPresentT) {
+ nsecs_t presentT = vsyncEventData.frameTimelines[i].expectedPresentationTime;
+ mCaptureToPresentOffset = presentT - t;
+ mLastCaptureTime = t;
+ mLastPresentTime = presentT;
+
+ // Move the expected presentation time back by 1/3 of frame interval to
+ // mitigate the time drift. Due to time drift, if we directly use the
+ // expected presentation time, often times 2 expected presentation time
+ // falls into the same VSYNC interval.
+ return presentT - vsyncEventData.frameInterval/3;
}
}
}