[libcamera-devel] [PATCH][RFC v2 0/2] qcam: viewfinder_gl: add RAW12P format support

[Andrey Konovalov]

I'd like to add that I would probably hold off on merging this patchset until I
post the RAW10P one. The latter is in progress, and when it is completed, it will
be more clear if reading the frame into GL_RGB texture (this is what the current
patchset does) vs GL_RED is the right choice.

Thanks,
Andrey

On 01.01.2021 20:15, Andrey Konovalov wrote:
> This patchset adds support for OpenGL accelerated conversion from 12-bit
> packed raw Bayer format (debyering).
> 
> All the 4 pixel layouts are supported, but only the RGGB one was tested.
> 
> The lower 4 bits of the 12-bit colour values are discarded as the target RGBA
> format has only 8 bits per colour.
> 
> Changes in v2 vs v1 [1]:
> * Most of the review comments are addressed. In particular:
>    * comments explaining the calculations in the shader are added
>    * textureUniformY_ is reused in the same way as RGB formats do
>    * uniforms are renamed to follow the common pattern
>    * the existing float tex_stepx is extended to vec2 tex_step and is
>      used in both YUV_packed and bayer_12_packed shaders
>    * firstRed_ type changed to QPointF
>    * NOT CHANGED: the center is still vec4, and [xy]coords are still vec2.
>      The reason is that I'd like to keep them in the same form as in the
>      original code [2] - I still consider moving from the current bilinear
>      to the MHC filter implemented in [2] someday.
> * The shader code is reworked to address the issue with the garbage due
>    to scaling the image from the captured size to the viewfinder window size.
>    With v1 one could see something like [3], and in v2 this is fixed [4].
>    For this all the processing is moved to the fragment shader, so that the
>    hardware interpolators don't have the effect (the price is increased GPU
>    load). [PATCH][RFC 1/2] "qcam: viewfinder_gl: set the vertex shader file
>    name in selectFormat()" is dropped as the common identity vertex shader is
>    used in v2.
> * The header in the fragment shader is updated to refer to the work [2] this
>    shader is based on. The license is adjusted accordingly.
> 
> [1] https://lists.libcamera.org/pipermail/libcamera-devel/2020-November/014893.html
> [2] https://casual-effects.com/research/McGuire2009Bayer/index.html
> [3] https://people.linaro.org/~andrey.konovalov/qcam-vf_gl-raw12p/v1_maximized.bmp
> [4] https://people.linaro.org/~andrey.konovalov/qcam-vf_gl-raw12p/v2-1_maximized.bmp
> 
>