[libcamera-devel] [PATCH v3 4/4] ipu3: cio2: Tweak sensor size selection policy
Umang Jain
umang.jain at ideasonboard.com
Mon Aug 30 10:21:50 CEST 2021
Do not compare higher precision of the ratios, as it might lead to
absurd selection of sensor size for a relatively low requested
resolution size.
For example:
The imx258 driver supports the following sensor resolutions:
- 4208x3118 = 1.349583066
- 2104x1560 = 1.348717949
- 1048x780 = 1.343589744
It can be inferred that, that the aspect ratio only differs by a small
factor with each other. It does not makes sense to select a 4208x3118
for a requested size of say 640x480 or 1280x720, which is what is
happening currently.
($) cam -c1 -swidth=640,height=480,role=raw
- CIO2 configuration: 4208x3118-SGRBG10_IPU3
In order to address this constraint, only compare the ratio with single
precision to make a better decision on the sensor resolution policy
selection.
($) cam -c1 -srole=raw,width=640,height=480
- CIO2 configuration: 1048x780-SGRBG10_IPU3
Signed-off-by: Umang Jain <umang.jain at ideasonboard.com>
Tested-by: Jacopo Mondi <jacopo at jmondi.org>
Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>
Reviewed-by: Kieran Bingham <kieran.bingham at ideasonboard.com>
---
src/libcamera/pipeline/ipu3/cio2.cpp | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/src/libcamera/pipeline/ipu3/cio2.cpp b/src/libcamera/pipeline/ipu3/cio2.cpp
index ceaf665e..9cedcb5b 100644
--- a/src/libcamera/pipeline/ipu3/cio2.cpp
+++ b/src/libcamera/pipeline/ipu3/cio2.cpp
@@ -295,6 +295,14 @@ V4L2SubdeviceFormat CIO2Device::getSensorFormat(const std::vector<unsigned int>
continue;
float ratio = static_cast<float>(sz.width) / sz.height;
+ /*
+ * Ratios can differ by small mantissa difference which
+ * can affect the selection of the sensor output size
+ * wildly. We are interested in selection of the closest
+ * size with respect to the desired output size, hence
+ * comparing it with a single precision digit is enough.
+ */
+ ratio = static_cast<unsigned int>(ratio * 10) / 10.0;
float ratioDiff = fabsf(ratio - desiredRatio);
unsigned int area = sz.width * sz.height;
unsigned int areaDiff = area - desiredArea;
--
2.31.1
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