linux-kernel - Re: [PATCH v2 2/6] [media] Documentation: Add HSV format

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Date:	Sat, 16 Jul 2016 10:19:29 +0200
From:	Hans Verkuil <hverkuil@...all.nl>
To:	Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
Cc:	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Laurent Pinchart <laurent.pinchart+renesas@...asonboard.com>,
	Sakari Ailus <sakari.ailus@...ux.intel.com>,
	Antti Palosaari <crope@....fi>,
	Guennadi Liakhovetski <guennadi.liakhovetski@...el.com>,
	Helen Mae Koike Fornazier <helen.koike@...labora.co.uk>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Shuah Khan <shuahkh@....samsung.com>,
	linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 2/6] [media] Documentation: Add HSV format

On 07/15/2016 08:11 PM, Laurent Pinchart wrote:
> Hi Ricardo,
> 
> Thank you for the patch.
> 
> On Friday 15 Jul 2016 18:13:15 Ricardo Ribalda Delgado wrote:
>> Describe the HSV formats
>>
>> Signed-off-by: Ricardo Ribalda Delgado <ricardo.ribalda@...il.com>
>> ---
>>  Documentation/media/uapi/v4l/hsv-formats.rst       |  19 ++
>>  Documentation/media/uapi/v4l/pixfmt-packed-hsv.rst | 253 ++++++++++++++++++
>>  Documentation/media/uapi/v4l/pixfmt.rst            |   1 +
>>  Documentation/media/uapi/v4l/v4l2.rst              |   5 +
>>  4 files changed, 278 insertions(+)
>>  create mode 100644 Documentation/media/uapi/v4l/hsv-formats.rst
>>  create mode 100644 Documentation/media/uapi/v4l/pixfmt-packed-hsv.rst
>>
>> diff --git a/Documentation/media/uapi/v4l/hsv-formats.rst
>> b/Documentation/media/uapi/v4l/hsv-formats.rst new file mode 100644
>> index 000000000000..f0f2615eaa95
>> --- /dev/null
>> +++ b/Documentation/media/uapi/v4l/hsv-formats.rst
>> @@ -0,0 +1,19 @@
>> +.. -*- coding: utf-8; mode: rst -*-
>> +
>> +.. _hsv-formats:
>> +
>> +***********
>> +HSV Formats
>> +***********
>> +
>> +These formats store the color information of the image
>> +in a geometrical representation. The colors are mapped into a
>> +cylinder, where the angle is the HUE, the height is the VALUE
>> +and the distance to the center is the SATURATION. This is a very
>> +useful format for image segmentation algorithms.
>> +
>> +
>> +.. toctree::
>> +    :maxdepth: 1
>> +
>> +    pixfmt-packed-hsv
>> diff --git a/Documentation/media/uapi/v4l/pixfmt-packed-hsv.rst
>> b/Documentation/media/uapi/v4l/pixfmt-packed-hsv.rst new file mode 100644
>> index 000000000000..b297aa4f7ba6
>> --- /dev/null
>> +++ b/Documentation/media/uapi/v4l/pixfmt-packed-hsv.rst
>> @@ -0,0 +1,253 @@
>> +.. -*- coding: utf-8; mode: rst -*-
>> +
>> +.. _packed-hsv:
>> +
>> +******************
>> +Packed HSV formats
>> +******************
>> +
>> +*man Packed HSV formats(2)*
>> +
>> +Packed HSV formats
>> +
>> +
>> +Description
>> +===========
>> +
>> +The HUE (h) is meassured in degrees, one LSB represents two degrees.
> 
> Is this common ? I have a device that can handle HSV data, I need to check how 
> it maps the hue values to binary, but I'm pretty sure they cover the full 
> 0-255 range. We would then have to support the two formats. Separate 4CCs are 
> an option, but reporting the range separately (possibly through the colorspace 
> API) might be better. Any thought on that ?

It's either a separate 4cc or we do something with the ycbcr_enc field (reinterpreted
as hsv_enc). I'm not sure, I would have to think some more about that.

Regards,

	Hans