[RFQ] Multiple ISP outputs and scaler crop

[Kieran Bingham]

Quoting Naushir Patuck (2024-05-01 10:26:14)
> Hi all,
> 
> We have come across some new use cases where users will need different
> scaler crops applied to each of the 2 ISP outputs configured by the
> application.  This is not possible on the VC4 hardware, but we can
> apply different crop configurations on Pi5/PISP.
> 
> Right now, libcamera has a single ScalerCrop control that we apply to
> both outputs.  This means that the input FoV is identical for both
> outputs, and can distort the pixel aspect ratio on the "low res"
> output if the output aspect ratio on both ISP outputs are not the
> same.
> 
> I would like to propose a couple of solutions to this:
> 
> 1) Change the ScalerCrop control to be a span, so that users can
> specify crop for multiple output branches through the single control.
> This will incur an API breakage though, so may not be desirable.
> 
> 2) Add a new control called ScalerCrops (with an s), that behaves
> identically to ScalerCrop, but works with a span of rectangles.  The
> value is handled in exactly the same way as  ScalerCrop, but allows
> the user to set muitple crops, one per output.  Of course the wording
> of this control needs to be explicit about the behavior, e.g. index 0
> corresponds to configured stream 0, and what if we only want to change
> one stream's scaler crop, etc.
> 
> Thoughts?

Shouldn't this be a control on a Stream?
I think the difficulty is we don't yet have 'stream' controls. What
other controls are there that can apply distinctly on different output
streams?

--
Kieran


> 
> Regards,
> Naush