[libcamera-devel] Raw streams and video

[David Plowman]

Hi everyone

I wanted to raise a topic that I've run into recently. One of the
features I want to implement is the ability to capture raw video
(meaning the raw Bayer frames from the sensor). In this use case we
might typically be capturing binned frames from the sensor.

Originally I'd thought that all I need is Naush's set of raw stream
patches, however, now that they've appeared I'm not so sure.

1. The current StillCaptureRaw role seems inappropriate. It forces the
use of the full sensor resolution (I realise this is something I
wanted at the time!) and requests a small number of buffers.

2. I wonder whether it would be appropriate to introduce a "VideoRaw"
role. This could default to a larger number of buffers and not force
the maximum resolution. In fact, we would need to treat its resolution
quite differently - it would have no effect on selecting a resolution
(other streams would determine that), but would have its details
filled in after configure() has chosen the camera mode.

One minor point is that the stream configurations don't "know" what
role they have, is that right? That would make it difficult for
configure() to distinguish "StillCaptureRaw" streams from "VideoRaw"
streams, so maybe there's something to think about there.

Anyway, apologies if I've started another meta-discussion. Thoughts
welcome, as always!

Best regards
David