Re: [PATCH 2/3] Document 8-bit and 16-bit YCrCb media bus pixel codes

[Christian Gmeiner <christian.gmeiner@gmail.com>]

2011/7/11 Christian Gmeiner <christian.gmeiner@gmail.com>:
> Hi Laurent,
>
> 2011/7/11 Laurent Pinchart <laurent.pinchart@ideasonboard.com>:
>> Hi Christian,
>>
>> On Sunday 10 July 2011 20:14:21 Christian Gmeiner wrote:
>>> Signed-off-by: Christian Gmeiner
>>> ---
>>> diff --git a/Documentation/DocBook/media/v4l/subdev-formats.xml
>>> b/Documentation/DocBook/media/v4l/subdev-formats.xml
>>> index 49c532e..18e30b0 100644
>>> --- a/Documentation/DocBook/media/v4l/subdev-formats.xml
>>> +++ b/Documentation/DocBook/media/v4l/subdev-formats.xml
>>> @@ -2565,5 +2565,43 @@
>>>         </tgroup>
>>>        </table>
>>>      </section>
>>> +
>>> +    <section>
>>> +      <title>YCrCb Formats</title>
>>> +
>>> +      <para>YCbCr represents colors as a combination of three values:
>>> +      <itemizedlist>
>>> +       <listitem><para>Y - the luminosity (roughly the
>>> brightness)</para></listitem>
>>> +       <listitem><para>Cb - the chrominance of the blue
>>> primary</para></listitem>
>>> +       <listitem><para>Cr - the chrominance of the red
>>> primary</para></listitem>
>>
>> How does that differ from YUV ?
>
>
> I need to say that I am very new to this whole format stuff and so I
> am not really sure.
> In the data sheet
> http://dxr3.sourceforge.net/download/hardware/ADV7175A_6A.pdf there is
> on the
> first page a FUNCTIONAL BLOCK DIAGRAM which shows that there is a
> "YCrCb to YUV Matrix"
> stage in the pipeline. I am also fine to use a YUV format for the media bus.
> Any suggestions?


Okay I think I have found the difference between YUV and YCrCb - see [1]

YCbCr 4:2:2
(Redirected from YUV 4:2:2)

FourCCs: YUY2, UYVY, YUV2 (Apple Component Video stored in MOV files)
Samples: http://samples.mplayerhq.hu/V-codecs/YUV2/

(These FourCC names only reflect that the YCbCr of digital media is
often falsely mixed up with analog PAL's YUV color space.)

YCbCr 4:2:2 is a packed YCbCr format in which a pair of consecutive
pixels is represented by 1 Y sample each but share a Cb sample and a
Cr sample.

This type of data may be packaged in a container format with a a
FourCC of YUY2 which indicates the following byte formatting:


[1] http://wiki.multimedia.cx/index.php?title=YUV_4:2:2

Greets,
--
Christian Gmeiner, MSc