[libcamera-devel] [PATCH] android: camera_device: Fix exposure time tag in exif and android

[Laurent Pinchart]

Hi Paul,

Thank you for the patch.

On Thu, Jan 28, 2021 at 07:22:14PM +0900, Paul Elder wrote:
> The exposure time libcamera control is in microseconds while android and
> our exif component use nanoseconds. Convert it appropriately.
> 
> CTS also expects the exposure time exif tag to match the exposure time
> set in the android result metadata. Fix it.
> 
> Signed-off-by: Paul Elder <paul.elder at ideasonboard.com>
> ---
>  src/android/camera_device.cpp            | 2 +-
>  src/android/jpeg/post_processor_jpeg.cpp | 3 ++-
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/src/android/camera_device.cpp b/src/android/camera_device.cpp
> index f5066709..36382941 100644
> --- a/src/android/camera_device.cpp
> +++ b/src/android/camera_device.cpp
> @@ -2058,7 +2058,7 @@ CameraDevice::getResultMetadata(Camera3RequestDescriptor *descriptor,
>  	}
>  
>  	if (metadata.contains(controls::ExposureTime)) {
> -		int32_t exposure = metadata.get(controls::ExposureTime);
> +		int64_t exposure = metadata.get(controls::ExposureTime) * 1000;

The calculation will overflow for long exposure times.

		int64_t exposure = metadata.get(controls::ExposureTime) * 1000ULL;

After addressing Jacopo's comments,

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

>  		resultMetadata->addEntry(ANDROID_SENSOR_EXPOSURE_TIME,
>  					 &exposure, 1);
>  	}
> diff --git a/src/android/jpeg/post_processor_jpeg.cpp b/src/android/jpeg/post_processor_jpeg.cpp
> index cac0087b..6250b050 100644
> --- a/src/android/jpeg/post_processor_jpeg.cpp
> +++ b/src/android/jpeg/post_processor_jpeg.cpp
> @@ -113,7 +113,8 @@ int PostProcessorJpeg::process(const FrameBuffer &source,
>  	exif.setTimestamp(std::time(nullptr), 0ms);
>  
>  	/* \todo Get this information from libcamera::Request::metadata */
> -	exif.setExposureTime(0);
> +	ret = resultMetadata->getEntry(ANDROID_SENSOR_EXPOSURE_TIME, &entry);
> +	exif.setExposureTime(ret ? *entry.data.i64 : 0);
>  	ret = requestMetadata.getEntry(ANDROID_LENS_APERTURE, &entry);
>  	if (ret)
>  		exif.setAperture(*entry.data.f);

-- 
Regards,

Laurent Pinchart