Re: [PATCH 2/2] media: iris: add new rate control type MBR for encoder

[Sachin Kumar Garg <sachin.garg@oss.qualcomm.com>]

On 3/17/2026 12:17 AM, Dmitry Baryshkov wrote:
> On Mon, Mar 16, 2026 at 01:37:21PM -0400, Nicolas Dufresne wrote:
>> Le lundi 16 mars 2026 à 11:52 +0530, Sachin Kumar Garg a écrit :
>>>
>>>
>>> On 2/13/2026 3:24 PM, Konrad Dybcio wrote:
>>>> On 2/13/26 7:04 AM, Sachin Kumar Garg wrote:
>>>>> Introduce V4L2_MPEG_VIDEO_BITRATE_MODE_MBR rate control to Encoder.
>>>>> Encoder will choose appropriate quantization parameter and
>>>>> do the smart bit allocation to set the frame maximum bitrate
>>>>> level as per the Bitrate value configured.
>>>>> ---
>>>>>    drivers/media/platform/qcom/iris/iris_ctrls.c      |   2 +
>>>>>    .../platform/qcom/iris/iris_hfi_gen1_defines.h     |   1 +
>>>>>    .../media/platform/qcom/iris/iris_platform_gen1.c  |   9 +-
>>>>>    .../platform/qcom/iris/iris_platform_sc7280.h      | 202
>>>>> +++++++++++++++++++++
>>>>
>>>> Is this really only available on 7280?
>>>>
>>>> Konrad
>>>
>>> Yes Konrad, in this series we enable V4L2_MPEG_VIDEO_BITRATE_MODE_MBR
>>> only for SC7280 because currently, we have added the support only for
>>> low tier chipset. MBR rate control aims to improve the compression
>>> efficiency of encoder for static and low motion scenes for extremely low
>>> bitrate use-case.
>>
>> Without a spec definition, which constrained the implementations toward
>> interoperability, this needs to be made vendor specific. That being said, even
>> as vendor specific control, I think it deserves more documentation for your
>> users.
> 
> What kind of documentation would be a better fit for keeping this in the
> generic namespace? Frankly speaking, I think that the current
> documentation is too vendor-specific, it describe the particular
> algorithm, while the control seems to be more generic. However, I also
> feel that defining it as "Maximum Bitrate" might not be specific enough
> (nor would it show a difference from the CBR mode).
> 
> 
Thanks for the suggestion.
I understand that this functionality is vendor-specific and should not 
be exposed via a generic control. Would it be acceptable to convert this 
into a vendor-specific control (for example, 
V4L2_MPEG_VIDEO_BITRATE_MODE_QCOM_MBR) and update the documentation 
accordingly?
Please let me know if this aligns with upstream expectations, or can you 
please suggest if there is any other preferred approach for adding 
vendor-specific controls in this case.

Thanks,
Sachin