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Date: Wed, 2 Dec 2020 15:09:30 +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, linux-arm-kernel@...ts.infradead.org
Cc: Kyungmin Park <kyungmin.park@...sung.com>,
Kamil Debski <kamil@...as.org>,
Ezequiel Garcia <ezequiel@...labora.com>,
Nicolas Dufresne <nicolas.dufresne@...labora.com>,
Marek Szyprowski <m.szyprowski@...sung.com>
Subject: Re: [PATCH 1/4] v4l2-ctrl: Make display delay and display enable std
controls
On 09/11/2020 18:35, Stanimir Varbanov wrote:
> Make display delay and display delay enable MFC controls standard v4l
> controls. This will allow reuse of the controls for other decoder
> drivers. Also the new proposed controls are now codec agnostic because
> they could be used for any codec.
>
> Signed-off-by: Stanimir Varbanov <stanimir.varbanov@...aro.org>
> ---
> .../userspace-api/media/v4l/ext-ctrls-codec.rst | 15 +++++++++++++++
> drivers/media/v4l2-core/v4l2-ctrls.c | 4 ++++
> include/uapi/linux/v4l2-controls.h | 2 ++
> 3 files changed, 21 insertions(+)
>
> diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> index ce728c757eaf..82c9cda40270 100644
> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
> @@ -679,6 +679,21 @@ enum v4l2_mpeg_video_frame_skip_mode -
> otherwise the decoder expects a single frame in per buffer.
> Applicable to the decoder, all codecs.
>
> +``V4L2_CID_MPEG_VIDEO_DECODER_DISPLAY_DELAY_ENABLE (boolean)``
I'd use _DEC_ instead of _DECODER_.
> + If the display delay is enabled then the decoder is forced to return
> + a CAPTURE buffer (decoded frame) after processing a certain number
> + of OUTPUT buffers. The delay can be set through
> + ``V4L2_CID_MPEG_VIDEO_DECODER_DISPLAY_DELAY``. This
> + feature can be used for example for generating thumbnails of videos.
> + Applicable to the decoder.
Hmm. Is this: "after processing the first 'display delay' number of OUTPUT buffers."
Or is this: "every 'display delay' number of OUTPUT buffers."
I.e., is it a one-shot thing or a periodical thing?
If it is a one-shot thing, then this should probably be a button type, not
a boolean.
> +
> +``V4L2_CID_MPEG_VIDEO_DECODER_DISPLAY_DELAY (integer)``
> + Display delay value for decoder. The decoder is forced to
> + return a decoded frame after the set 'display delay' number of
> + frames. If this number is low it may result in frames returned out
> + of display order, in addition the hardware may still be using the
> + returned buffer as a reference picture for subsequent frames.
Can this be 0? And if so, what does that mean?
> +
> ``V4L2_CID_MPEG_VIDEO_H264_VUI_SAR_ENABLE (boolean)``
> Enable writing sample aspect ratio in the Video Usability
> Information. Applicable to the H264 encoder.
> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c b/drivers/media/v4l2-core/v4l2-ctrls.c
> index bd7f330c941c..4a21802e026b 100644
> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
> @@ -874,6 +874,8 @@ const char *v4l2_ctrl_get_name(u32 id)
> case V4L2_CID_MPEG_VIDEO_HEADER_MODE: return "Sequence Header Mode";
> case V4L2_CID_MPEG_VIDEO_MAX_REF_PIC: return "Max Number of Reference Pics";
> case V4L2_CID_MPEG_VIDEO_FRAME_SKIP_MODE: return "Frame Skip Mode";
> + case V4L2_CID_MPEG_VIDEO_DECODER_DISPLAY_DELAY: return "Display Delay";
> + case V4L2_CID_MPEG_VIDEO_DECODER_DISPLAY_DELAY_ENABLE: return "Display Delay Enable";
> case V4L2_CID_MPEG_VIDEO_H263_I_FRAME_QP: return "H263 I-Frame QP Value";
> case V4L2_CID_MPEG_VIDEO_H263_P_FRAME_QP: return "H263 P-Frame QP Value";
> case V4L2_CID_MPEG_VIDEO_H263_B_FRAME_QP: return "H263 B-Frame QP Value";
> @@ -1221,6 +1223,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
> case V4L2_CID_FLASH_READY:
> case V4L2_CID_MPEG_VIDEO_DECODER_MPEG4_DEBLOCK_FILTER:
> case V4L2_CID_MPEG_VIDEO_DECODER_SLICE_INTERFACE:
> + case V4L2_CID_MPEG_VIDEO_DECODER_DISPLAY_DELAY_ENABLE:
> case V4L2_CID_MPEG_VIDEO_FRAME_RC_ENABLE:
> case V4L2_CID_MPEG_VIDEO_MB_RC_ENABLE:
> case V4L2_CID_MPEG_VIDEO_H264_8X8_TRANSFORM:
> @@ -1256,6 +1259,7 @@ void v4l2_ctrl_fill(u32 id, const char **name, enum v4l2_ctrl_type *type,
> break;
> case V4L2_CID_MPEG_VIDEO_MV_H_SEARCH_RANGE:
> case V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE:
> + case V4L2_CID_MPEG_VIDEO_DECODER_DISPLAY_DELAY:
> *type = V4L2_CTRL_TYPE_INTEGER;
> break;
> case V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME:
> diff --git a/include/uapi/linux/v4l2-controls.h b/include/uapi/linux/v4l2-controls.h
> index 7035f4fb182c..d6b19f8d0022 100644
> --- a/include/uapi/linux/v4l2-controls.h
> +++ b/include/uapi/linux/v4l2-controls.h
> @@ -773,6 +773,8 @@ enum v4l2_mpeg_video_frame_skip_mode {
> V4L2_MPEG_VIDEO_FRAME_SKIP_MODE_LEVEL_LIMIT = 1,
> V4L2_MPEG_VIDEO_FRAME_SKIP_MODE_BUF_LIMIT = 2,
> };
> +#define V4L2_CID_MPEG_VIDEO_DECODER_DISPLAY_DELAY (V4L2_CID_MPEG_BASE + 647)
> +#define V4L2_CID_MPEG_VIDEO_DECODER_DISPLAY_DELAY_ENABLE (V4L2_CID_MPEG_BASE + 648)
This will need to be rebased once this PR is merged:
https://patchwork.linuxtv.org/project/linux-media/patch/d68da172-b251-000f-653d-38a8a4c7b715@xs4all.nl/
>
> /* MPEG-class control IDs specific to the CX2341x driver as defined by V4L2 */
> #define V4L2_CID_MPEG_CX2341X_BASE (V4L2_CTRL_CLASS_MPEG | 0x1000)
>
Regards,
Hans
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