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

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Message-ID: <152b080b-59aa-4081-2be0-e86f85b2b3b8@osg.samsung.com>
Date:   Tue, 21 Feb 2017 15:04:34 -0300
From:   Thibault Saunier <thibault.saunier@....samsung.com>
To:     Andrzej Hajda <a.hajda@...sung.com>, linux-kernel@...r.kernel.org
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Kukjin Kim <kgene@...nel.org>,
        Mauro Carvalho Chehab <mchehab@...pensource.com>,
        Nicolas Dufresne <nicolas.dufresne@...labora.com>,
        Andi Shyti <andi.shyti@...sung.com>,
        linux-media@...r.kernel.org, Shuah Khan <shuahkh@....samsung.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        linux-samsung-soc@...r.kernel.org,
        Krzysztof Kozlowski <krzk@...nel.org>,
        Inki Dae <inki.dae@...sung.com>,
        Sylwester Nawrocki <s.nawrocki@...sung.com>,
        linux-arm-kernel@...ts.infradead.org,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Hans Verkuil <hverkuil@...all.nl>
Subject: Re: [PATCH v4 1/4] [media] exynos-gsc: Use 576p instead 720p as a
 threshold for colorspaces

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@....samsung.com>
>>
>> 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@....samsung.com>
>> Signed-off-by: Thibault Saunier <thibault.saunier@....samsung.com>
>> Reviewed-by: Andrzej Hajda <a.hajda@...sung.com>
> 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@...sung.com>'
>>
>> 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;
>