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

[Dmitry Baryshkov]

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).


-- 
With best wishes
Dmitry