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

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Date:   Tue, 08 Dec 2020 22:14:22 +0530
From:   dikshita@...eaurora.org
To:     Hans Verkuil <hverkuil-cisco@...all.nl>
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.

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.

Thanks,
Dikshita

> Regards,
> 
> 	Hans