Camera: Reduce latency for dejittering
There is a tradeoff between dejittering and latency. The more we delay
the presentation of frames, the longer latency there is.
- Only look ahead for 2 frames in the vsync timeline. And do not exceed
2+1 vsync timestamps when spacing out fixed frame rates in lockstep with
display vsync.
- Disable synchronizing presentation time to vsync for variable frame
rate. Fixed frame rate and video mode is typically more tolerant to
higher latency and prefers smoother user experience.
- Reduce the upper bound of holding onto buffers to 10ms.
Test: Measure photon-to-photon latency
Bug: 239775097
Change-Id: I601a0fadf89529922fd1bd5d0a17ba80832b4cab
diff --git a/services/camera/libcameraservice/device3/Camera3OutputStream.cpp b/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
index 8b3cf44..84b5aa4 100644
--- a/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
+++ b/services/camera/libcameraservice/device3/Camera3OutputStream.cpp
@@ -1410,18 +1410,24 @@
}
nsecs_t Camera3OutputStream::syncTimestampToDisplayLocked(nsecs_t t) {
+ nsecs_t currentTime = systemTime();
+ if (!mFixedFps) {
+ mLastCaptureTime = t;
+ mLastPresentTime = currentTime;
+ return t;
+ }
+
ParcelableVsyncEventData parcelableVsyncEventData;
auto res = mDisplayEventReceiver.getLatestVsyncEventData(&parcelableVsyncEventData);
if (res != OK) {
ALOGE("%s: Stream %d: Error getting latest vsync event data: %s (%d)",
__FUNCTION__, mId, strerror(-res), res);
mLastCaptureTime = t;
- mLastPresentTime = t;
+ mLastPresentTime = currentTime;
return t;
}
const VsyncEventData& vsyncEventData = parcelableVsyncEventData.vsync;
- nsecs_t currentTime = systemTime();
nsecs_t minPresentT = mLastPresentTime + vsyncEventData.frameInterval / 2;
// Find the best presentation time without worrying about previous frame's
@@ -1526,8 +1532,8 @@
}
}
- if (expectedPresentT == mLastPresentTime && expectedPresentT <=
- vsyncEventData.frameTimelines[maxTimelines].expectedPresentationTime) {
+ if (expectedPresentT == mLastPresentTime && expectedPresentT <
+ vsyncEventData.frameTimelines[maxTimelines-1].expectedPresentationTime) {
// Couldn't find a reasonable presentation time. Using last frame's
// presentation time would cause a frame drop. The best option now
// is to use the next VSync as long as the last presentation time
diff --git a/services/camera/libcameraservice/device3/Camera3OutputStream.h b/services/camera/libcameraservice/device3/Camera3OutputStream.h
index 741bca2..db988a0 100644
--- a/services/camera/libcameraservice/device3/Camera3OutputStream.h
+++ b/services/camera/libcameraservice/device3/Camera3OutputStream.h
@@ -432,7 +432,7 @@
static constexpr nsecs_t kSpacingResetIntervalNs = 50000000LL; // 50 millisecond
static constexpr nsecs_t kTimelineThresholdNs = 1000000LL; // 1 millisecond
static constexpr float kMaxIntervalRatioDeviation = 0.05f;
- static constexpr int kMaxTimelines = 3;
+ static constexpr int kMaxTimelines = 2;
nsecs_t syncTimestampToDisplayLocked(nsecs_t t);
// Re-space frames by delaying queueBuffer so that frame delivery has
diff --git a/services/camera/libcameraservice/device3/PreviewFrameSpacer.cpp b/services/camera/libcameraservice/device3/PreviewFrameSpacer.cpp
index 67f42b4..b3cb178 100644
--- a/services/camera/libcameraservice/device3/PreviewFrameSpacer.cpp
+++ b/services/camera/libcameraservice/device3/PreviewFrameSpacer.cpp
@@ -68,7 +68,7 @@
return true;
}
- // Cache the frame to match readout time interval, for up to 33ms
+ // Cache the frame to match readout time interval, for up to kMaxFrameWaitTime
nsecs_t expectedQueueTime = mLastCameraPresentTime + readoutInterval;
nsecs_t frameWaitTime = std::min(kMaxFrameWaitTime, expectedQueueTime - currentTime);
if (frameWaitTime > 0 && mPendingBuffers.size() < 2) {
diff --git a/services/camera/libcameraservice/device3/PreviewFrameSpacer.h b/services/camera/libcameraservice/device3/PreviewFrameSpacer.h
index e165768..cb9690c 100644
--- a/services/camera/libcameraservice/device3/PreviewFrameSpacer.h
+++ b/services/camera/libcameraservice/device3/PreviewFrameSpacer.h
@@ -85,7 +85,7 @@
nsecs_t mLastCameraPresentTime = 0;
static constexpr nsecs_t kWaitDuration = 5000000LL; // 50ms
static constexpr nsecs_t kFrameIntervalThreshold = 80000000LL; // 80ms
- static constexpr nsecs_t kMaxFrameWaitTime = 33333333LL; // 33ms
+ static constexpr nsecs_t kMaxFrameWaitTime = 10000000LL; // 10ms
};
}; //namespace camera3
