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([2606:6d00:17:7b4b::5ac]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-890770e2aa5sm203968666d6.19.2026.01.15.05.51.24 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 15 Jan 2026 05:51:25 -0800 (PST) Message-ID: Subject: Re: [RFC PATCH 1/3] media: uapi: Introduce new control for video encoder ROI From: Nicolas Dufresne To: Deepa Guthyappa Madivalara , Mauro Carvalho Chehab , Vikash Garodia , Dikshita Agarwal , Abhinav Kumar , Bryan O'Donoghue Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org Date: Thu, 15 Jan 2026 08:51:23 -0500 In-Reply-To: <763b6cdd-514c-4aff-b7db-8c0a17fdb645@oss.qualcomm.com> References: <20260113-iris_enc_roi-v1-0-6c86eba38587@oss.qualcomm.com> <20260113-iris_enc_roi-v1-1-6c86eba38587@oss.qualcomm.com> <08ff44d8907c72b7599fa4599477d78bcecb440a.camel@ndufresne.ca> <763b6cdd-514c-4aff-b7db-8c0a17fdb645@oss.qualcomm.com> Autocrypt: addr=nicolas@ndufresne.ca; prefer-encrypt=mutual; keydata=mDMEaCN2ixYJKwYBBAHaRw8BAQdAM0EHepTful3JOIzcPv6ekHOenE1u0vDG1gdHFrChD /e0J05pY29sYXMgRHVmcmVzbmUgPG5pY29sYXNAbmR1ZnJlc25lLmNhPoicBBMWCgBEAhsDBQsJCA cCAiICBhUKCQgLAgQWAgMBAh4HAheABQkJZfd1FiEE7w1SgRXEw8IaBG8S2UGUUSlgcvQFAmibrjo CGQEACgkQ2UGUUSlgcvQlQwD/RjpU1SZYcKG6pnfnQ8ivgtTkGDRUJ8gP3fK7+XUjRNIA/iXfhXMN abIWxO2oCXKf3TdD7aQ4070KO6zSxIcxgNQFtDFOaWNvbGFzIER1ZnJlc25lIDxuaWNvbGFzLmR1Z nJlc25lQGNvbGxhYm9yYS5jb20+iJkEExYKAEECGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4 AWIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCaCyyxgUJCWX3dQAKCRDZQZRRKWBy9ARJAP96pFmLffZ smBUpkyVBfFAf+zq6BJt769R0al3kHvUKdgD9G7KAHuioxD2v6SX7idpIazjzx8b8rfzwTWyOQWHC AAS0LU5pY29sYXMgRHVmcmVzbmUgPG5pY29sYXMuZHVmcmVzbmVAZ21haWwuY29tPoiZBBMWCgBBF iEE7w1SgRXEw8IaBG8S2UGUUSlgcvQFAmibrGYCGwMFCQll93UFCwkIBwICIgIGFQoJCAsCBBYCAw ECHgcCF4AACgkQ2UGUUSlgcvRObgD/YnQjfi4+L8f4fI7p1pPMTwRTcaRdy6aqkKEmKsCArzQBAK8 bRLv9QjuqsE6oQZra/RB4widZPvphs78H0P6NmpIJ Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=-4EfGdaMvYDV/uoQuviha" User-Agent: Evolution 3.58.2 (3.58.2-1.fc43) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 --=-4EfGdaMvYDV/uoQuviha Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Hi, Le mercredi 14 janvier 2026 =C3=A0 16:20 -0800, Deepa Guthyappa Madivalara = a =C3=A9crit=C2=A0: > > > +``V4L2_CID_MPEG_VIDEO_ENC_ROI (struct)`` > > > +=C2=A0=C2=A0=C2=A0 Defines the control id to configure specific delt= a QP for one or more > > > +=C2=A0=C2=A0=C2=A0 rectangular regions of interest. The struct v4l2_= ctrl_enc_roi_params > > > +=C2=A0=C2=A0=C2=A0 is defined to hold up to 10 v4l2_rect regions and= their corresponding > > > +=C2=A0=C2=A0=C2=A0 delta_qp with a range of -31 to 30. > > > +=C2=A0=C2=A0=C2=A0 Applicable to encoders > > Any justification for this range ? Also, I believe I've seen hardware s= upport > > both delta and absolute values. Since it meant to be generic, some rese= arch is > > needed. If we delibaritly ignore absolute, perhaps the CID should be na= med > > accordingly ? Something like V4L2_CID_MPEG_VIDEO_ENC__DELTAQP_ROI ? >=20 > As per Android ROI API - MediaCodec API QP from the app is an offset QP, > meaning userspace will received offset Qp and it converts it to deltaQp > before passing onto the driver in Android HAL. I have used the same idea. > Delta MbQP =3D frame QP + Offset Qp. This is clamped to -31 to 30 current= ly > and set to driver as delta QP, hence I have it as -31 to 30. >=20 > Absolute values are mostly for frame QP, I would say. All the=20 > information out there for ROI > kind of implies to deltaQP, but we could be more precise as well. > Let me know if it is a must to change to CID. That's exactly what I want to avoid, hardcoding Android HAL into V4L2 witho= ut having our own rational and documentation. Also, Android HAL is a much olde= r API then D3D and Vulkan, and its not as well defined.The second is hardcoding r= ange for one specific implementation. Since this is codec agnostic, and hardware agnostic control, I would prefer is defined in a way that it requires no sc= aling by the driver. IIRC, some codec have QP values from 0 to 63, so why don't w= e allo from -63 to 63 ? The alternative is to let the driver expose its range= , but its a little tricky, you will have to specify when this information is avai= lable in the Stateful Video Encoder spec. As for the rest, you haven't considered extensibility in your proposal, wha= t if a non Qualcomm hardware do have features like aboslute QP ? (Hantro/VSI doe= s btw). How do we add that in a clean way ? Nicolas --=-4EfGdaMvYDV/uoQuviha Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCaWjw2wAKCRDZQZRRKWBy 9D1SAP92tas3kEN9sDLF5yOfgNqtSCxbbQfo0nV1bDsItRBDGAD/cYxdAq6tgbL8 UU2md8W1C/BDvJH5koiRccSeGHuK9wQ= =4KtW -----END PGP SIGNATURE----- --=-4EfGdaMvYDV/uoQuviha--