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

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Date:   Tue, 14 Feb 2017 15:19:37 +0000
From:   Fabien DESSENNE <fabien.dessenne@...com>
To:     Thibault Saunier <thibault.saunier@....samsung.com>,
        "linux-kernel@...r.kernel.org" <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" <linux-media@...r.kernel.org>,
        Shuah Khan <shuahkh@....samsung.com>,
        Javier Martinez Canillas <javier@....samsung.com>,
        "linux-samsung-soc@...r.kernel.org" 
        <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" 
        <linux-arm-kernel@...ts.infradead.org>,
        Ulf Hansson <ulf.hansson@...aro.org>
Subject: Re: [PATCH v4 1/4] [media] exynos-gsc: Use 576p instead 720p as a
 threshold for colorspaces

Hi Thibault


On 13/02/17 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

typo -> "V4L2_COLORSPACE_REC709 instead of V4L2_COLORSPACE_SMPTE170M"


> 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>
>
> ---
>
> 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;

BR
Fabien