Re: [PATCH v2 2/8] [media] Add signed 16-bit pixel format

From: Nick Dyer
Date: Fri May 27 2016 - 08:52:51 EST

On 27/05/2016 13:38, Hans Verkuil wrote:
> On 05/04/2016 07:07 PM, Nick Dyer wrote:
>> + <refname><constant>V4L2_PIX_FMT_YS16</constant></refname>
>> + <refpurpose>Grey-scale image</refpurpose>
>> + </refnamediv>
>> + <refsect1>
>> + <title>Description</title>
>> +
>> + <para>This is a signed grey-scale image with a depth of 16 bits per
>> +pixel. The most significant byte is stored at higher memory addresses
>> +(little-endian).</para>
> I'm not sure this should be described in terms of grey-scale, since negative
> values make no sense for that. How are these values supposed to be interpreted
> if you want to display them? -32768 == black and 32767 is white?

We have written a utility to display this data and it is able to display
the values mapped to grayscale or color:

An example of the output is here:

The data is intrinsically signed because that's how the low level touch
controller treats it. I'm happy to change it to "Signed image" if you think
that would be better.