linux-kernel - Re: [PATCH v4] media: v4l2-ctrl: add control for long term reference.

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Message-ID: <6c6f56ce-750b-0706-1ff0-46adefcfe542@xs4all.nl>
Date:   Tue, 8 Dec 2020 17:45:37 +0100
From:   Hans Verkuil <hverkuil-cisco@...all.nl>
To:     dikshita@...eaurora.org
Cc:     linux-media@...r.kernel.org, nicolas@...fresne.ca,
        stanimir.varbanov@...aro.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, vgarodia@...eaurora.org
Subject: Re: [PATCH v4] media: v4l2-ctrl: add control for long term reference.

On 08/12/2020 17:44, dikshita@...eaurora.org wrote:
> Hi Hans,
> 
> On 2020-12-02 19:18, Hans Verkuil wrote:
>> On 01/12/2020 09:13, 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@...eaurora.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 3b86959..40634f8 100644
>>> --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>>> +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec.rst
>>> @@ -4450,3 +4450,21 @@ 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.
>>> +
>>> +``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.
>>> +       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.
>>> diff --git a/drivers/media/v4l2-core/v4l2-ctrls.c 
>>> b/drivers/media/v4l2-core/v4l2-ctrls.c
>>> index e5b726f..0b81b39 100644
>>> --- a/drivers/media/v4l2-core/v4l2-ctrls.c
>>> +++ b/drivers/media/v4l2-core/v4l2-ctrls.c
>>> @@ -958,6 +958,9 @@ 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";
>>
>> "Frame LTR Index"
>>
>>> +	case V4L2_CID_MPEG_VIDEO_USE_LTR_FRAMES:		return "Use LTR Frame(s)";
>>
>> Just: "Use LTR Frames". No '(s)'.
>>
>>>  	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_MPEG_VIDEO_FWHT_PARAMS:			return "FWHT Stateless 
>>> Parameters";
>>> @@ -1273,6 +1276,17 @@ 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 e37b85f..710bc53 100644
>>> --- a/include/uapi/linux/v4l2-controls.h
>>> +++ b/include/uapi/linux/v4l2-controls.h
>>> @@ -421,6 +421,9 @@ enum v4l2_mpeg_video_multi_slice_mode {
>>>  #define 
>>> V4L2_CID_MPEG_VIDEO_MV_H_SEARCH_RANGE		(V4L2_CID_MPEG_BASE+227)
>>>  #define 
>>> V4L2_CID_MPEG_VIDEO_MV_V_SEARCH_RANGE		(V4L2_CID_MPEG_BASE+228)
>>>  #define V4L2_CID_MPEG_VIDEO_FORCE_KEY_FRAME		(V4L2_CID_MPEG_BASE+229)
>>> +#define V4L2_CID_MPEG_VIDEO_LTR_COUNT                  
>>> (V4L2_CID_MPEG_BASE + 230)
>>> +#define V4L2_CID_MPEG_VIDEO_FRAME_LTR_INDEX            
>>> (V4L2_CID_MPEG_BASE + 231)
>>> +#define V4L2_CID_MPEG_VIDEO_USE_LTR_FRAMES             
>>> (V4L2_CID_MPEG_BASE + 232)
>>>
>>>  /* CIDs for the MPEG-2 Part 2 (H.262) codec */
>>>  #define V4L2_CID_MPEG_VIDEO_MPEG2_LEVEL			(V4L2_CID_MPEG_BASE+270)
>>>
>>
>> Note that this and the other patches from you that add
>> V4L2_CID_MPEG_VIDEO controls
>> will need to be rebased as soon as this PR is merged:
>>
>> https://patchwork.linuxtv.org/project/linux-media/patch/d68da172-b251-000f-653d-38a8a4c7b715@xs4all.nl/
>>
>> I recommend waiting until that's in.
>>
>> I currently have the following patches from you adding new controls
>> besides this one:
>>
>> https://patchwork.linuxtv.org/project/linux-media/patch/1606121442-31074-1-git-send-email-dikshita@codeaurora.org/
>> https://patchwork.linuxtv.org/project/linux-media/patch/1605682497-29273-2-git-send-email-dikshita@codeaurora.org/
>> https://patchwork.linuxtv.org/project/linux-media/patch/1605682497-29273-3-git-send-email-dikshita@codeaurora.org/
>>
>> What is missing is driver support for these new controls. I recommend 
>> that, once
>> the PR mentioned above is merged, you make a new series combining all 
>> three
>> patches + patches that add support for this to the venus driver.
>>
> I will address all comments in the next version and will include driver 
> implementation as well.
> Once all the driver changes are reviewed, I will make a series with all 
> final patches, Hope that's fine.

That sounds great!

Regards,

	Hans

> 
> Thanks,
> Dikshita
> 
>> Regards,
>>
>> 	Hans