linux-kernel - Re: [PATCH 1/2] v4l2-ctrl: Add decoder conceal color control

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Date:   Tue, 9 Feb 2021 12:05:28 +0100
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     Stanimir Varbanov <stanimir.varbanov@...aro.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH 1/2] v4l2-ctrl: Add decoder conceal color control

On 09/02/2021 10:45, Stanimir Varbanov wrote:
> Add decoder v4l2 control to set conceal color.
> 
> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>
> ---
>  .../media/v4l/ext-ctrls-codec.rst             | 20 +++++++++++++++++++
>  drivers/media/v4l2-core/v4l2-ctrls.c          |  9 +++++++++
>  include/uapi/linux/v4l2-controls.h            |  1 +
>  3 files changed, 30 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> index 00944e97d638..994650052333 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -674,6 +674,26 @@ enum v4l2_mpeg_video_frame_skip_mode -
>      is currently displayed (decoded). This value is reset to 0 whenever
>      the decoder is started.
>  
> +``V4L2_CID_MPEG_VIDEO_DEC_CONCEAL_COLOR (integer64)``
> +    This control sets conceal color in YUV color space. It describes the
> +    client preference of error conceal color in case of error where
> +    reference frame is missing. The decoder would paint the reference
> +    buffer with preferred color and use it for future decoding.
> +    Applicable to decoders.

You should mention explicitly that this is using 16-bit color components
and expects Limited Range.

> +
> +.. flat-table::
> +    :header-rows:  0
> +    :stub-columns: 0
> +
> +    * - Bit 0:15
> +      - Y luminance
> +    * - Bit 16:31
> +      - Cb chrominance
> +    * - Bit 32:47
> +      - Cr chrominance
> +    * - Bit 48:63
> +      - Must be zero
> +
>  ``V4L2_CID_MPEG_VIDEO_DECODER_SLICE_INTERFACE (boolean)``
>      If enabled the decoder expects to receive a single slice per buffer,
>      otherwise the decoder expects a single frame in per buffer.
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index 016cf6204cbb..a3b9d28a00b7 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -945,6 +945,7 @@ const char *v4l2_ctrl_get_name(u32 id)
>  	case V4L2_CID_MPEG_VIDEO_VBV_SIZE:			return "VBV Buffer Size";
>  	case V4L2_CID_MPEG_VIDEO_DEC_PTS:			return "Video Decoder PTS";
>  	case V4L2_CID_MPEG_VIDEO_DEC_FRAME:			return "Video Decoder Frame Count";
> +	case V4L2_CID_MPEG_VIDEO_DEC_CONCEAL_COLOR:		return "Video Decoder Conceal Color";
>  	case V4L2_CID_MPEG_VIDEO_VBV_DELAY:			return "Initial Delay for VBV Control";
>  	case V4L2_CID_MPEG_VIDEO_MV_H_SEARCH_RANGE:		return "Horizontal MV Search Range";
>  	case V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE:		return "Vertical MV Search Range";
> @@ -1430,6 +1431,14 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
>  		*max = 0x7fffffffffffffffLL;
>  		*step = 1;
>  		break;
> +	case V4L2_CID_MPEG_VIDEO_DEC_CONCEAL_COLOR:
> +		*type = V4L2_CTRL_TYPE_INTEGER64;
> +		*min = 0;
> +		/* default for 8bit black, luma is 16, chroma is 128 */

Since this is 16 bit the actual default luma value for black is 4096 and for chroma use
32768 (i.e. both values are times 256).

> +		*def = 0x8000800010LL;
> +		*max = 0xffffffffffffLL;
> +		*step = 1;
> +		break;
>  	case V4L2_CID_PIXEL_RATE:
>  		*type = V4L2_CTRL_TYPE_INTEGER64;
>  		*flags |= V4L2_CTRL_FLAG_READ_ONLY;
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> index 039c0d7add1b..5e5a3068be2d 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -428,6 +428,7 @@ enum v4l2_mpeg_video_multi_slice_mode {
>  #define V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE		(V4L2_CID_CODEC_BASE+228)
>  #define V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME		(V4L2_CID_CODEC_BASE+229)
>  #define V4L2_CID_MPEG_VIDEO_BASELAYER_PRIORITY_ID	(V4L2_CID_CODEC_BASE+230)
> +#define V4L2_CID_MPEG_VIDEO_DEC_CONCEAL_COLOR		(V4L2_CID_CODEC_BASE+231)
>  
>  /* CIDs for the MPEG-2 Part 2 (H.262) codec */
>  #define V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL			(V4L2_CID_CODEC_BASE+270)
> 

Regards,

	Hans