RFC: HSV format

RFC: HSV format

[Ricardo Ribalda Delgado]

Hi

HSV is a  cylindrical-coordinate representation of a color. It is very
useful for computer vision because the Hue component can be used to
segment a scene.

My plan was to add a format in videodev2.h and then add support for
vivid, libv4l2-convert and qv4l2.

There are also plans to prepare a patch for opencv to use this format
without any software conversion, and also for Gstreamer... but all
these changes depend on the changes on videodev2.h

The question is how open would be the linux-media community for such a
change, considering that there is no real device driver using it in
tree ( Our hardware is currently out of tree_

Today we only have an HSV format on v4l2-mediabus.h
V4L2_MBUS_FROM_MEDIA_BUS_FMT(AHSV8888_1X32), but no HSV format on
videodev2.h


Thanks!!!



-- 
Ricardo Ribalda

Re: RFC: HSV format

[Hans Verkuil]

On 05/24/2016 11:19 PM, Ricardo Ribalda Delgado wrote:
> Hi
> 
> HSV is a  cylindrical-coordinate representation of a color. It is very
> useful for computer vision because the Hue component can be used to
> segment a scene.
> 
> My plan was to add a format in videodev2.h and then add support for
> vivid, libv4l2-convert and qv4l2.
> 
> There are also plans to prepare a patch for opencv to use this format
> without any software conversion, and also for Gstreamer... but all
> these changes depend on the changes on videodev2.h
> 
> The question is how open would be the linux-media community for such a
> change, considering that there is no real device driver using it in
> tree ( Our hardware is currently out of tree_
> 
> Today we only have an HSV format on v4l2-mediabus.h
> V4L2_MBUS_FROM_MEDIA_BUS_FMT(AHSV8888_1X32), but no HSV format on
> videodev2.h

It's always a bit tricky to decide what to do with this. In general I feel
uncomfortable with the idea of defines that aren't used. Certainly for very
hardware-specific formats I don't like the idea of adding unused formats to
the kernel.

In this case I am however inclined to accept it provided:

- it's not a crazy format: e.g. AHSV (32 bit) or HSV (24 bit) would be fine,
  but some weird macroblock format would be a lot more problematic.
- it's fully documented
- implemented in vivid etc.
- patches adding it to opencv/gstreamer are CC-ed to linux-media as well so
  I know that it is going to be used there.

But you will have to check with Mauro as well, he has the final say in this.

Regards,

	Hans