Re: [PATCH v4 1/4] [media] exynos-gsc: Use 576p instead 720p as a threshold for colorspaces

[Thibault Saunier]

Hello Andrzej,

On 02/21/2017 06:56 AM, Andrzej Hajda wrote:
> On 13.02.2017 20:08, Thibault Saunier wrote:
> > From: Javier Martinez Canillas <javier@xxxxxxxxxxxxxxx>
> >
> > The media documentation says that the V4L2_COLORSPACE_SMPTE170M colorspace
> > should be used for SDTV and V4L2_COLORSPACE_REC709 for HDTV. But drivers
> > don't agree on the display resolution that should be used as a threshold.
> >
> > >From EIA CEA 861B about colorimetry for various resolutions:
> >
> >    - 5.1 480p, 480i, 576p, 576i, 240p, and 288p
> >      The color space used by the 480-line, 576-line, 240-line, and 288-line
> >      formats will likely be based on SMPTE 170M [1].
> >    - 5.2 1080i, 1080p, and 720p
> >      The color space used by the high definition formats will likely be
> >      based on ITU-R BT.709-4
> >
> > This indicates that in the case that userspace does not specify what
> > colorspace should be used, we should use 576p  as a threshold to set
> > V4L2_COLORSPACE_REC709 instead of V4L2_COLORSPACE_REC709. Even if it is
> > only 'likely' and not a requirement it is the best guess we can make.
> >
> > The stream should have been encoded with the information and userspace
> > has to pass it to the driver if it is not the case, otherwise we won't be
> > able to handle it properly anyhow.
> >
> > Also, check for the resolution in G_FMT instead unconditionally setting
> > the V4L2_COLORSPACE_REC709 colorspace.
> >
> > Signed-off-by: Javier Martinez Canillas <javier@xxxxxxxxxxxxxxx>
> > Signed-off-by: Thibault Saunier <thibault.saunier@xxxxxxxxxxxxxxx>
> > Reviewed-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>
> Hi Thibault,
>
> Have you analyzed Hans response for the previous patchset [1] ?
> I am not an expert in the subject but it seems he is right. GSCALER
> datasheet uses term 'color space conversion' to describe conversions
> between RGB and YCbCr, not for describe colorspaces as in V4L2.
> GSC_(IN|OUT)_RGB_(HD|SD)_(WIDE|NARROW) macros used to set IN_CON and
> OUT_CON registers of GSCALER are probably used incorrectly, they should
> not be set according to pix_mp->colorspace but rather according to
> pix_mp->ycbcr_enc and pix_mp->quantization. pix_mp->colorspace should be
> just copied from output to capture side.
>
> Please fix the patch accordingly, and if you are interested you can
> prepare another patch to fix register setting.

OK, so what you describe here for the colorspace  is exactly what I am 
doing in my next patch right?
I am going to fixup them up as suggested in your other review.

I will also have a look at fixing register setting and figure out what 
you explained.

Thanks for the review.

Regards,

Thibault Saunier

> [1]: https://lkml.org/lkml/2017/2/10/473
>
> Regards
> Andrzej
>
> > ---
> >
> > Changes in v4:
> > - Reword commit message to better back our assumptions on specifications
> >
> > Changes in v3:
> > - Do not check values in the g_fmt functions as Andrzej explained in previous review
> > - Added 'Reviewed-by: Andrzej Hajda <a.hajda@xxxxxxxxxxx>'
> >
> > Changes in v2: None
> >
> >   drivers/media/platform/exynos-gsc/gsc-core.c | 8 ++++++--
> >   1 file changed, 6 insertions(+), 2 deletions(-)
> >
> > diff --git a/drivers/media/platform/exynos-gsc/gsc-core.c b/drivers/media/platform/exynos-gsc/gsc-core.c
> > index 59a634201830..db7d9883861b 100644
> > --- a/drivers/media/platform/exynos-gsc/gsc-core.c
> > +++ b/drivers/media/platform/exynos-gsc/gsc-core.c
> > @@ -472,7 +472,7 @@ int gsc_try_fmt_mplane(struct gsc_ctx *ctx, struct v4l2_format *f)
> >   
> >   	pix_mp->num_planes = fmt->num_planes;
> >   
> > -	if (pix_mp->width >= 1280) /* HD */
> > +	if (pix_mp->width > 720 && pix_mp->height > 576) /* HD */
> >   		pix_mp->colorspace = V4L2_COLORSPACE_REC709;
> >   	else /* SD */
> >   		pix_mp->colorspace = V4L2_COLORSPACE_SMPTE170M;
> > @@ -519,9 +519,13 @@ int gsc_g_fmt_mplane(struct gsc_ctx *ctx, struct v4l2_format *f)
> >   	pix_mp->height		= frame->f_height;
> >   	pix_mp->field		= V4L2_FIELD_NONE;
> >   	pix_mp->pixelformat	= frame->fmt->pixelformat;
> > -	pix_mp->colorspace	= V4L2_COLORSPACE_REC709;
> >   	pix_mp->num_planes	= frame->fmt->num_planes;
> >   
> > +	if (pix_mp->width > 720 && pix_mp->height > 576) /* HD */
> > +		pix_mp->colorspace = V4L2_COLORSPACE_REC709;
> > +	else /* SD */
> > +		pix_mp->colorspace = V4L2_COLORSPACE_SMPTE170M;
> > +
> >   	for (i = 0; i < pix_mp->num_planes; ++i) {
> >   		pix_mp->plane_fmt[i].bytesperline = (frame->f_width *
> >   			frame->fmt->depth[i]) / 8;