[libcamera-devel] [PATCH] android: Apply 1% tolerance to minFrameDuration capping

[Umang Jain]

We have some stream resolution which can provide slightly better
frame duration than what we cap (i.e. 1/30 fps). The problem with
this is CTS complains if the camera goes faster during the test
than minFrameDuration reported for that resolution. For instance,

1080p minFrameDuration:
	- Nautilus : 33282000ns
	- Soraka   : 33147000ns

Both are less than capped minFrameDuration 1/30 fps (33333333.33ns).

This patch considers this situation and doesn't cap the
minFrameDuration if the hardware can provide frame durations slightly
better. The tolerance considered is 1% only from the cap.

Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
---
On LIMITED level - no regressions were found : 230/231 pass rate

On FULL level - this fixes the test:
android.hardware.camera2.cts.SurfaceViewPreviewTest#testPreviewFpsRange
---
 src/android/camera_capabilities.cpp | 16 +++++++++++++---
 1 file changed, 13 insertions(+), 3 deletions(-)

diff --git a/src/android/camera_capabilities.cpp b/src/android/camera_capabilities.cpp
index f357902e..c4c26089 100644
--- a/src/android/camera_capabilities.cpp
+++ b/src/android/camera_capabilities.cpp
@@ -648,7 +648,7 @@ int CameraCapabilities::initializeStreamConfigurations()
 			int64_t maxFrameDuration = frameDurations->second.max().get<int64_t>() * 1000;
 
 			/*
-			 * Cap min frame duration to 30 FPS.
+			 * Cap min frame duration to 30 FPS with 1% tolerance.
 			 *
 			 * 30 frames per second has been validated as the most
 			 * opportune frame rate for quality tuning, and power
@@ -667,8 +667,18 @@ int CameraCapabilities::initializeStreamConfigurations()
 			 * control to be specified for each Request. Defer this
 			 * to the in-development configuration API rework.
 			 */
-			if (minFrameDuration < 1e9 / 30.0)
-				minFrameDuration = 1e9 / 30.0;
+			int64_t minFrameDurationCap = 1e9 / 30.0;
+			if (minFrameDuration < minFrameDurationCap) {
+				float tolerance =
+					(minFrameDurationCap - minFrameDuration) * 100.0 / minFrameDurationCap;
+
+				/*
+				 * If the tolerance is less than 1%, do not cap
+				 * the frame duration.
+				 */
+				if (tolerance > 1.0)
+					minFrameDuration = minFrameDurationCap;
+			}
 
 			streamConfigurations_.push_back({
 				res, androidFormat, minFrameDuration, maxFrameDuration,
-- 
2.31.0