linux-kernel - Re: [RFC PATCH 0/3] Implement Region of Interest(ROI) support.

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Message-ID: <d7b2d31b-e643-43cb-8f16-9568944222d6@oss.qualcomm.com>
Date: Wed, 14 Jan 2026 14:14:18 -0800
From: Deepa Guthyappa Madivalara <deepa.madivalara@....qualcomm.com>
To: Nicolas Dufresne <nicolas@...fresne.ca>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Vikash Garodia <vikash.garodia@....qualcomm.com>,
        Dikshita Agarwal <dikshita.agarwal@....qualcomm.com>,
        Abhinav Kumar <abhinav.kumar@...ux.dev>,
        Bryan O'Donoghue <bod@...nel.org>
Cc: linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [RFC PATCH 0/3] Implement Region of Interest(ROI) support.


On 1/14/2026 8:08 AM, Nicolas Dufresne wrote:
> Hi,
>
> Le mardi 13 janvier 2026 à 12:33 -0800, Deepa Guthyappa Madivalara a écrit :
>> Hi all,
>>
>> This patch set implements region of interest(ROI) support
>> for video encoder to be configured as a rectangular
>> region, and corresponding delta QP parameter. A new compound
>> control V4L2_CID_MPEG_VIDEO_ENC_ROI which maps to struct
>> v4l2_ctrl_enc_roi_params is implemented to achieve this.
> My very first question will be why ROI rather then QP Map ? Its seems that
> modern API such as D3D12 and Vulkan Video aims for QP Map instead of a limited
> set of rectangles, while older hardware / firmware have ROI, but since you are
> saying that this is not yet implemented in your firmware, I thought it was worth
> asking.
>
> The ROI are relatively easy to convert into QP Maps, but the opposite is going
> to be a lot less accurate. That being said, the number of ROI can be extremely
> limited, at least this is the case for Samsung MFC firmware and Hantro encoders
> (no upstream driver yet).
>
> let us know your thought, should we adopt just one, and have driver translate
> once HW moved to the new approach ? Should we enventually support both ?
>
> Nicolas

Hi Nicolas,

Thanks for the quick comments.
Qp map for can be too much data to be sent from user space to firmware 
via control per frame.
Ex: Avc has mbsize as 16 and the max mbpf iris driver supports is 8192x4352.
This would mean 136kb of data (8bit Qp) needs to be transferred for each 
frame in worst case.
While are still evaluating Qp map option, due to firmware performance 
issues we are
gravitating more towards rectangle ROI.
I am not sure if we will need to support the Qp map in the future.

>> I'm sharing this series as an RFC because adding support
>> in the firmware and framework for testing, gstreamer testing
>> is still in progress. I would appreciate early feedback on
>> the design, implementation, and fixes before moving to a
>> formal submission.
>>
>> v4l2-ctl -d /dev/video1 --list-ctrls
>> ..
>> hevc_b_frame_maximum_qp_value 0x00990b8c (int): min=1 max=51 step=1
>> default=51 value=51 flags=has-min-max
>> video_encoder_roi_params 0x00990b92 (unknown): type=284
>> value=unsupported payload type flags=has-payload
>>
>> Thanks,
>> Deepa
>>
>> Signed-off-by: Deepa Guthyappa Madivalara <deepa.madivalara@....qualcomm.com>
>> ---
>> Deepa Guthyappa Madivalara (3):
>>        media: uapi: Introduce new control for video encoder ROI
>>        media: v4l2-core: Add support for video encoder ROI control
>>        media: iris: Add ROI support framework for video encoder
>>
>>   .../userspace-api/media/v4l/ext-ctrls-codec.rst    |  7 +++
>>   drivers/media/platform/qcom/iris/iris_ctrls.c      | 54
>> +++++++++++++++++++++-
>>   drivers/media/platform/qcom/iris/iris_ctrls.h      |  1 +
>>   .../platform/qcom/iris/iris_platform_common.h      |  4 ++
>>   .../media/platform/qcom/iris/iris_platform_gen2.c  |  8 ++++
>>   drivers/media/v4l2-core/v4l2-ctrls-core.c          | 14 +++++-
>>   drivers/media/v4l2-core/v4l2-ctrls-defs.c          |  5 ++
>>   include/media/v4l2-ctrls.h                         |  1 +
>>   include/uapi/linux/v4l2-controls.h                 |  1 +
>>   include/uapi/linux/videodev2.h                     | 17 +++++++
>>   10 files changed, 110 insertions(+), 2 deletions(-)
>> ---
>> base-commit: f417b7ffcbef7d76b0d8860518f50dae0e7e5eda
>> change-id: 20260112-iris_enc_roi-8898f9a2455f
>>
>> Best regards,