[libcamera-devel] [PATCH v6 1/6] libcamera: controls: Add sensor test pattern mode

[Laurent Pinchart]

Hi Hiro,

Thank you for the patch.

On Fri, May 28, 2021 at 12:05:26PM +0900, Hirokazu Honda wrote:
> The control is used to report available sensor test pattern modes
> and also specify the mode to sensor.
> 
> Signed-off-by: Hirokazu Honda <hiroh at chromium.org>
> Reviewed-by: Jacopo Mondi <jacopo at jmondi.org>
> ---
>  src/libcamera/control_ids.yaml | 58 ++++++++++++++++++++++++++++++++++
>  1 file changed, 58 insertions(+)
> 
> diff --git a/src/libcamera/control_ids.yaml b/src/libcamera/control_ids.yaml
> index 88d81ac4..b1fe1dc6 100644
> --- a/src/libcamera/control_ids.yaml
> +++ b/src/libcamera/control_ids.yaml
> @@ -615,4 +615,62 @@ controls:
>          detection, additional format conversions etc) count as an additional
>          pipeline stage.
>  
> +  - TestPatternMode:
> +      type: int32_t
> +      draft: true
> +      description: |
> +        Control to select the test pattern mode. Currently identical to
> +        ANDROID_SENSOR_TEST_PATTERN_MODE.

I'd add that the test pattern modes are identical to the ones defined by
the CCS specification. Maybe something along the lines of:

	The modes are described in a pixel-perfect way in the MIPI
	Camera Command Set (https://www.mipi.org/specifications/camera-command-set)
	specification.

I've wondered for a long time how we could standardize test pattern
modes when there's no standard at the hardware level, and I've been
pointed out recently to the fact that CCS defines pixel-perfect test
patterns (they are parametrized by a set of read-only parameters
reported by the sensor though, the specification is worth a read). This
comes from the SMIA++ specification that also standardized test pattern
modes, but from what I've been told, not in a pixel-perfect way.

Apart from that, this looks good to me for now as it's a draft control.
We'll have to decide how to handle custom patterns once we destage this
control.

> +      enum:
> +        - name: TestPatternModeOff
> +          value: 0
> +          description: |
> +            No test pattern mode is used. The camera device returns frames from
> +            the image sensor.
> +        - name: TestPatternModeSolidColor
> +          value: 1
> +          description: |
> +            Each pixel in [R, G_even, G_odd, B] is replaced by its respective
> +            color channel provided in test pattern data.
> +            \todo Add control for test pattern data.
> +        - name: TestPatternModeColorBars
> +          value: 2
> +          description: |
> +            All pixel data is replaced with an 8-bar color pattern. The vertical
> +            bars (left-to-right) are as follows; white, yellow, cyan, green,
> +            magenta, red, blue and black. Each bar should take up 1/8 of the
> +            sensor pixel array width. When this is not possible, the bar size
> +            should be rounded down to the nearest integer and the pattern can
> +            repeat on the right side. Each bar's height must always take up the
> +            full sensor pixel array height.
> +        - name: TestPatternModeColorBarsFadeToGray
> +          value: 3
> +          description: |
> +            The test pattern is similar to TestPatternModeColorBars,
> +            except that each bar should start at its specified color at the top
> +            and fade to gray at the bottom. Furthermore each bar is further
> +            subdevided into a left and right half. The left half should have a
> +            smooth gradient, and the right half should have a quantized
> +            gradient. In particular, the right half's should consist of blocks
> +            of the same color for 1/16th active sensor pixel array width. The
> +            least significant bits in the quantized gradient should be copied
> +            from the most significant bits of the smooth gradient. The height of
> +            each bar should always be a multiple of 128. When this is not the
> +            case, the pattern should repeat at the bottom of the image.
> +        - name: TestPatternModePn9
> +          value: 4
> +          description: |
> +            All pixel data is replaced by a pseudo-random sequence generated
> +            from a PN9 512-bit sequence (typically implemented in hardware with
> +            a linear feedback shift register). The generator should be reset at
> +            the beginning of each frame, and thus each subsequent raw frame with
> +            this test pattern should be exactly the same as the last.
> +        - name: TestPatternModeCustom1
> +          value: 5

This starts at 256 in the Android camera HAL API, I'd do the same as the
control is documented as being identical to
ANDROID_SENSOR_TEST_PATTERN_MODE.

Reviewed-by: Laurent Pinchart <laurent.pinchart at ideasonboard.com>

> +          description: |
> +            The first custom test pattern. All custom patterns that are
> +            available only on this camera device are at least this numeric
> +            value. All of the custom test patterns will be static (that is the
> +            raw image must not vary from frame to frame).
> +
>  ...

-- 
Regards,

Laurent Pinchart