Re: [PATCH 2/2] zr36067: VIDIOC_S_FMT returns the colorspace value

[Jean Delvare <khali@xxxxxxxxxxxx>]

Hi Trent,

On Wed, 10 Sep 2008 13:25:02 -0700 (PDT), Trent Piepho wrote:
> On Sun, 7 Sep 2008, Jean Delvare wrote:
> > Ioctl VIDIOC_S_FMT is supposed to fill the colorspace value in the
> > returned buffer.
> >
> > +				fmt->fmt.pix.colorspace =
> > +				    V4L2_COLORSPACE_SMPTE170M;
> 
> This is probably the colorspace to use for NTSC, but for PAL it should
> probably be V4L2_COLORSPACE_470_SYSTEM_BG
> 
> Here's something that I wrote a while ago about colorspaces:
> http://article.gmane.org/gmane.comp.video.video4linux/30815
> 
> I imagine that the zoran chip just passes through the digital data it gets
> from the external video decoder, and so has nothing to do with the
> colorspace.
> 
> I don't know if the video decoders do any sort of colorspace conversion.
> They probably don't and the colorspace is just whatever the source signal
> is using, which is something the driver doesn't actually know.  Other than
> just assuming that NTSC will be SMPTE170M and PAL/SECAM will be Bt.470 B,G

I have to admit that I don't know a thing about colorspaces. The goal
of my patch was simply to make sure that the color space returned by
VIDIOC_S_FMT would be the same as that returned by a subsequent
VIDIOC_G_FMT. Apparently the Zoran driver only uses SMPTE170M at the
moment, not 470_SYSTEM_BG.

As the colorspaces are currently hard-coded in zoran_formats[], it
would need some changes to make the driver return different colorspaces
depending on the video norm. Do you think it is worth it?

-- 
Jean Delvare

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