[libcamera-devel] Fixing debayering?

[Rafael Diniz]

Thanks Laurent.

I tried many different resolutions, and I still get the artifacts.

I'm going down to debugging what the driver is delivering to user-space, 
as there could be something wrong in kernel space, so I want to be sure 
there is nothing wrong.

Rafael

On 7/6/22 10:16, Laurent Pinchart wrote:
> Hi Rafael,
> 
> On Wed, Jul 06, 2022 at 02:37:04PM +0300, Rafael Diniz wrote:
>> Thanks Laurent.
>>
>> I'm wondering if the frames SBGGR8 passed to this code are in the
>> required format...
>> /** Monochrome RGBA or GL_LUMINANCE Bayer encoded texture.*/
> 
> That part should be fine. In ViewFinderGL::doRender(), for RAW8 formats,
> we have
> 
> 		glTexImage2D(GL_TEXTURE_2D,
> 			     0,
> 			     GL_LUMINANCE,
> 			     stride_,
> 			     size_.height(),
> 			     0,
> 			     GL_LUMINANCE,
> 			     GL_UNSIGNED_BYTE,
> 			     image_->data(0).data());
> 
> With GL_LUMINANCE + GL_UNSIGNED_BYTE, the texture sampler will read the
> texture with one byte per pixel, and store the value of the byte in the
> .r, .g and .b components (scaled from [0, 255] to [0.0, 1.0]). The
> fragment shader then uses the .r component only.
> 
> One point to note is that the texture sampler will perform interpolation
> if the coordinates passed to it don't fall on a texel. For RAW8 formats,
> interpolation won't give correct results, as the sampler would try to
> interpolate between neighbour pixels with different colour filter. For
> that reason, ViewFinderGL::selectFormat() sets textureMinMagFilters_ to
> GL_NEAREST, which is then used in ViewFinderGL::configureTexture() to
> setup the min/mag filters. The lack of interpolation will affect the
> image quality when the display size is different than the capture size.
> 
>> Trying to dig a bit further.
>>
>> On 7/6/22 07:50, Laurent Pinchart wrote:
>>> On Wed, Jul 06, 2022 at 12:26:29PM +0300, Rafael Diniz via libcamera-devel wrote:
>>>> Hi all,
>>>>
>>>> The last annoying bug I can find in using qcam on the Pinephone (at
>>>> least on lower resolutions, as high resolutions are still borked) is the
>>>> debayering from SBGGR8, which is clearly producing artifacts. Where can
>>>> I find its implementation? I plan to read it and compare to the
>>>> canonical one and see what could be wrong.
>>>
>>> The implementation is in src/qcam/assets/shader/bayer_8.vert and
>>> src/qcam/assets/shader/bayer_8.frag.
> 
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