RE: [PATCH] ITU BT2020 support in v4l2_colorspace

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Hello Hans,
Thanks for you very quick feedback, it is my first patch and I'm happy it gets
some feedbacks.

> I'm not opposed to this, but have you actually seen video streams with this colorspace?
I work on silicon for set top boxes and we are indeed starting testing support
for BT2020 encode streams.


> More to the point, this colorspace is only valid for 10 and 12 bit deep colors 
> (something that should be documented as well), and I don't think we even
> have PIX_FMT defines for that. Are there plans to add support for that?

For the color space you are right, this is only valid for 10 & 12 bit deep colors
and current YUV formats do not explicitly state if pixel encoding is on 8,
10 or 12 bits as all formats so far used 8 bits encoding.

We do not plan to upstream our 10 bits formats because our HW has a really
fancy way of storing them and I doubt other hw vendor would do the same.
( no padding to 32 bits is performed ie the end of each YUV444 triplet starts 
with a new tripplet.)
Our driver code "quality" is far from beeing upstremable for the time beeing
so I did not think properly about "standard" 10/12 bits V4L2_PIX_FMT.

I can however propose a patch for PIX_FMT for 444, 420 and 422 10/8 bits
Let me know your thoughts about following naming scheme:

reuse any existing PIX_FMT name ( eg V4L2_PIX_FMT_NV16) and extend its
name with _10 or _12 on a need basis.

Other ways (to avoid creating a bunch of new names) could be:
- create 2 BT2020 entries in the color space (one for 10 bits one for 12 bits)
bitdepth would be inferred by those entries (not so nice)
- Add bit depth in v4l2_pix_format.priv 

Our current solution relies on extending the V4L2_PIX_FMT

Regards.
JM


-----Original Message-----
From: Hans Verkuil [mailto:hverkuil@xxxxxxxxx] 
Sent: vendredi 1 août 2014 17:10
To: Jean-Marc VOLLE; linux-media@xxxxxxxxxxxxxxx
Cc: Divneil Rai WADHAWAN
Subject: Re: [PATCH] ITU BT2020 support in v4l2_colorspace

On 08/01/2014 05:02 PM, Jean-Marc VOLLE wrote:
> From: vollejm <jean-marc.volle@xxxxxx>
> 
> UHD video content may be encoded using a new color space (BT2020). 
> This patch adds it to the  v4l2_colorspace enum

I'm not opposed to this, but have you actually seen video streams with this colorspace?

More to the point, this colorspace is only valid for 10 and 12 bit deep colors (something that should be documented as well), and I don't think we even have PIX_FMT defines for that. Are there plans to add support for that?

Regards,

	Hans

> 
> 
> Signed-off-by: <jean-marc.volle@xxxxxx>
> ---
>  Documentation/DocBook/media/v4l/biblio.xml | 10 ++++++++++  
> Documentation/DocBook/media/v4l/pixfmt.xml | 14 ++++++++++++++
>  include/uapi/linux/videodev2.h             |  4 ++++
>  3 files changed, 28 insertions(+)
> 
> diff --git a/Documentation/DocBook/media/v4l/biblio.xml 
> b/Documentation/DocBook/media/v4l/biblio.xml
> index d2eb79e..d3930cf 100644
> --- a/Documentation/DocBook/media/v4l/biblio.xml
> +++ b/Documentation/DocBook/media/v4l/biblio.xml
> @@ -117,6 +117,16 @@ url="http://www.itu.ch";>http://www.itu.ch</ulink>)</corpauthor>
>        <title>ITU-R Recommendation BT.1119 "625-line  television Wide 
> Screen Signalling (WSS)"</title>
>      </biblioentry>
> +    <biblioentry id="itu2020">
> +      <abbrev>ITU&nbsp;BT.2020</abbrev>
> +      <authorgroup>
> +	<corpauthor>International Telecommunication Union (<ulink 
> +url="http://www.itu.ch";>http://www.itu.ch</ulink>)</corpauthor>
> +      </authorgroup>
> +      <title>ITU-R Recommendation BT.2020 "Parameter values for
> +	      ultra-high definition television systems for production
> +	      and international programme exchange"</title>
> +    </biblioentry>
>  
>      <biblioentry id="jfif">
>        <abbrev>JFIF</abbrev>
> diff --git a/Documentation/DocBook/media/v4l/pixfmt.xml 
> b/Documentation/DocBook/media/v4l/pixfmt.xml
> index 91dcbc8..f0c70dd 100644
> --- a/Documentation/DocBook/media/v4l/pixfmt.xml
> +++ b/Documentation/DocBook/media/v4l/pixfmt.xml
> @@ -599,6 +599,20 @@ are still clamped to [0;255].</para>  
> 1.099&nbsp;I<superscript>0.45</superscript>&nbsp;-&nbsp;0.099&nbsp;for&nbsp;0.018&nbsp;&lt;&nbsp;I</entry>
>  	    <entry spanname="spam">n/a</entry>
>  	  </row>
> +	  <row>
> +	    <entry><constant>V4L2_COLORSPACE_BT2020</constant></entry>
> +	    <entry>9</entry>
> +	    <entry>BT2020, see <xref linkend="itu2020" /></entry>
> +	    <entry>x&nbsp;=&nbsp;0.708, y&nbsp;=&nbsp;0.292</entry>
> +	    <entry>x&nbsp;=&nbsp;0.170, y&nbsp;=&nbsp;0.797</entry>
> +	    <entry>x&nbsp;=&nbsp;0.131, y&nbsp;=&nbsp;0.046</entry>
> +	    <entry>x&nbsp;=&nbsp;0.3127, y&nbsp;=&nbsp;0.3290,
> +	    Illuminant D<subscript>65</subscript></entry>
> +	    <entry>see <xref linkend="itu2020" /></entry>
> +	    <entry>see <xref linkend="itu2020" /></entry>
> +	    <entry>see <xref linkend="itu2020" /></entry>
> +	    <entry>see <xref linkend="itu2020" /></entry>
> +	  </row>
>  	</tbody>
>        </tgroup>
>      </table>
> diff --git a/include/uapi/linux/videodev2.h 
> b/include/uapi/linux/videodev2.h index 168ff50..6af06e1 100644
> --- a/include/uapi/linux/videodev2.h
> +++ b/include/uapi/linux/videodev2.h
> @@ -197,6 +197,10 @@ enum v4l2_colorspace {
>  
>  	/* For RGB colourspaces, this is probably a good start. */
>  	V4L2_COLORSPACE_SRGB          = 8,
> +
> +	/* UHD BT2020 colorspace */
> +	V4L2_COLORSPACE_BT2020          = 9,
> +
>  };
>  
>  enum v4l2_priority {
> 

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