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Subject: Re: [PATCH v5 1/2] media: v4l2-ctrl: add control for long term
 reference.
To:     Dikshita Agarwal <dikshita@codeaurora.org>,
        linux-media@vger.kernel.org, stanimir.varbanov@linaro.org
Cc:     linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        vgarodia@codeaurora.org
References: <1609736971-14454-1-git-send-email-dikshita@codeaurora.org>
 <1609736971-14454-2-git-send-email-dikshita@codeaurora.org>
From:   Hans Verkuil <hverkuil-cisco@xs4all.nl>
Message-ID: <28e89e0c-3fd4-4d19-e4d2-5014e2be9398@xs4all.nl>
Date:   Tue, 12 Jan 2021 10:01:25 +0100
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On 04/01/2021 06:09, Dikshita Agarwal wrote:
> Long Term Reference (LTR) frames are the frames that are encoded
> sometime in the past and stored in the DPB buffer list to be used
> as reference to encode future frames.
> This change adds controls to enable this feature.
> 
> Signed-off-by: Dikshita Agarwal <dikshita@codeaurora.org>
> ---
>  .../userspace-api/media/v4l/ext-ctrls-codec.rst        | 18 ++++++++++++++++++
>  drivers/media/v4l2-core/v4l2-ctrls.c                   | 14 ++++++++++++++
>  include/uapi/linux/v4l2-controls.h                     |  3 +++
>  3 files changed, 35 insertions(+)
> 
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> index 400774c..1675bcf 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -3637,3 +3637,21 @@ enum v4l2_mpeg_video_hevc_size_of_length_field -
>        - Selecting this value specifies that HEVC slices are expected
>          to be prefixed by Annex B start codes. According to :ref:`hevc`
>          valid start codes can be 3-bytes 0x000001 or 4-bytes 0x00000001.
> +
> +``V4L2_CID_MPEG_VIDEO_LTR_COUNT (integer)``
> +       Specifies the number of Long Term Reference (LTR) frames encoder needs
> +       to generate or keep. This is applicable to H264 and HEVC encoder.

This is applicable to the H264 and HEVC encoders.

> +
> +``V4L2_CID_MPEG_VIDEO_FRAME_LTR_INDEX (integer)``
> +       The current frame is marked as a Long Term Reference (LTR) frame
> +       and given this LTR index which ranges from 0 to LTR_COUNT-1.
> +       This is applicable to H264 and HEVC encoder and can be applied using
> +       Request Api.

This is applicable to the H264 and HEVC encoders

Request Api -> the Request API

> +       Source Rec. ITU-T H.264 (06/2019); Table 7.9
> +
> +``V4L2_CID_MPEG_VIDEO_USE_LTR_FRAMES (bitmask)``
> +       Specifies the Long Term Reference (LTR) frame(s) to be used for
> +       encoding the current frame.
> +       This provides a bitmask which consists of bits [0, LTR_COUNT-1].
> +       This is applicable to H264 and HEVC encoder and can be applied using
> +       Request Api.

This is applicable to the H264 and HEVC encoders

Request Api -> the Request API

> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index 16ab54f..2ad6b5a 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -950,6 +950,9 @@ const char *v4l2_ctrl_get_name(u32 id)
>  	case V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE:		return "Vertical MV Search Range";
>  	case V4L2_CID_MPEG_VIDEO_REPEAT_SEQ_HEADER:		return "Repeat Sequence Header";
>  	case V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME:		return "Force Key Frame";
> +	case V4L2_CID_MPEG_VIDEO_LTR_COUNT:			return "LTR Count";
> +	case V4L2_CID_MPEG_VIDEO_FRAME_LTR_INDEX:		return "frame LTR index";

Use proper capitals:

"Frame LTR Index"

> +	case V4L2_CID_MPEG_VIDEO_USE_LTR_FRAMES:		return "Use LTR Frames";
>  	case V4L2_CID_MPEG_VIDEO_MPEG2_SLICE_PARAMS:		return "MPEG-2 Slice Parameters";
>  	case V4L2_CID_MPEG_VIDEO_MPEG2_QUANTIZATION:		return "MPEG-2 Quantization Matrices";
>  	case V4L2_CID_FWHT_I_FRAME_QP:				return "FWHT I-Frame QP Value";
> @@ -1277,6 +1280,17 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
>  	case V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE:
>  		*type = V4L2_CTRL_TYPE_INTEGER;
>  		break;
> +	case V4L2_CID_MPEG_VIDEO_LTR_COUNT:
> +		*type = V4L2_CTRL_TYPE_INTEGER;
> +		break;
> +	case V4L2_CID_MPEG_VIDEO_FRAME_LTR_INDEX:
> +		*type = V4L2_CTRL_TYPE_INTEGER;
> +		*flags |= V4L2_CTRL_FLAG_EXECUTE_ON_WRITE;
> +		break;
> +	case V4L2_CID_MPEG_VIDEO_USE_LTR_FRAMES:
> +		*type = V4L2_CTRL_TYPE_BITMASK;
> +		*flags |= V4L2_CTRL_FLAG_EXECUTE_ON_WRITE;
> +		break;
>  	case V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME:
>  	case V4L2_CID_PAN_RESET:
>  	case V4L2_CID_TILT_RESET:
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> index af8dda2..c0bb87b 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -422,6 +422,9 @@ enum v4l2_mpeg_video_multi_slice_mode {
>  #define V4L2_CID_MPEG_VIDEO_MV_H_SEARCH_RANGE		(V4L2_CID_CODEC_BASE+227)
>  #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_LTR_COUNT			(V4L2_CID_CODEC_BASE+230)
> +#define V4L2_CID_MPEG_VIDEO_FRAME_LTR_INDEX		(V4L2_CID_CODEC_BASE+231)
> +#define V4L2_CID_MPEG_VIDEO_USE_LTR_FRAMES		(V4L2_CID_CODEC_BASE+232)
>  
>  /* CIDs for the MPEG-2 Part 2 (H.262) codec */
>  #define V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL			(V4L2_CID_CODEC_BASE+270)
> 

Regards,

	Hans