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Thu, 28 Aug 2025 22:42:35 +0200 (CEST) Message-ID: <5065e67544ae9255b2136a6cd73cbb9ffd08e3fb.camel@collabora.com> Subject: Re: [PATCH v2 4/4] Documentation: media: Document V4L2_H264_DECODE_PARAM_FLAG_PFRAME/BFRAME From: Nicolas Dufresne To: Paul Kocialkowski , linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Mauro Carvalho Chehab , Hans Verkuil , Laurent Pinchart Date: Thu, 28 Aug 2025 16:42:32 -0400 In-Reply-To: <20250824180735.765587-5-paulk@sys-base.io> References: <20250824180735.765587-1-paulk@sys-base.io> <20250824180735.765587-5-paulk@sys-base.io> Autocrypt: addr=nicolas.dufresne@collabora.com; prefer-encrypt=mutual; keydata=mDMEaCN2ixYJKwYBBAHaRw8BAQdAM0EHepTful3JOIzcPv6ekHOenE1u0vDG1gdHFrChD /e0J05pY29sYXMgRHVmcmVzbmUgPG5pY29sYXNAbmR1ZnJlc25lLmNhPoicBBMWCgBEAhsDBQsJCA cCAiICBhUKCQgLAgQWAgMBAh4HAheABQkJZfd1FiEE7w1SgRXEw8IaBG8S2UGUUSlgcvQFAmibrjo CGQEACgkQ2UGUUSlgcvQlQwD/RjpU1SZYcKG6pnfnQ8ivgtTkGDRUJ8gP3fK7+XUjRNIA/iXfhXMN abIWxO2oCXKf3TdD7aQ4070KO6zSxIcxgNQFtDFOaWNvbGFzIER1ZnJlc25lIDxuaWNvbGFzLmR1Z nJlc25lQGNvbGxhYm9yYS5jb20+iJkEExYKAEECGwMFCwkIBwICIgIGFQoJCAsCBBYCAwECHgcCF4 AWIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCaCyyxgUJCWX3dQAKCRDZQZRRKWBy9ARJAP96pFmLffZ smBUpkyVBfFAf+zq6BJt769R0al3kHvUKdgD9G7KAHuioxD2v6SX7idpIazjzx8b8rfzwTWyOQWHC AAS0LU5pY29sYXMgRHVmcmVzbmUgPG5pY29sYXMuZHVmcmVzbmVAZ21haWwuY29tPoiZBBMWCgBBF iEE7w1SgRXEw8IaBG8S2UGUUSlgcvQFAmibrGYCGwMFCQll93UFCwkIBwICIgIGFQoJCAsCBBYCAw ECHgcCF4AACgkQ2UGUUSlgcvRObgD/YnQjfi4+L8f4fI7p1pPMTwRTcaRdy6aqkKEmKsCArzQBAK8 bRLv9QjuqsE6oQZra/RB4widZPvphs78H0P6NmpIJ Organization: Collabora Canada Content-Type: multipart/signed; micalg="pgp-sha512"; protocol="application/pgp-signature"; boundary="=-lValZJkHsUrv43G3L0AC" User-Agent: Evolution 3.56.2 (3.56.2-1.fc42) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 --=-lValZJkHsUrv43G3L0AC Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable Le dimanche 24 ao=C3=BBt 2025 =C3=A0 20:07 +0200, Paul Kocialkowski a =C3= =A9crit=C2=A0: > These flags are meant for a very specific use-case, add a mention of it. >=20 > Signed-off-by: Paul Kocialkowski > --- > =C2=A0.../userspace-api/media/v4l/ext-ctrls-codec-stateless.rst | 8 +++++= +-- > =C2=A01 file changed, 6 insertions(+), 2 deletions(-) >=20 > diff --git a/Documentation/userspace-api/media/v4l/ext-ctrls-codec-statel= ess.rst b/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.r= st > index 0da635691fdc..de1e3873385c 100644 > --- a/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst > +++ b/Documentation/userspace-api/media/v4l/ext-ctrls-codec-stateless.rst > @@ -618,10 +618,14 @@ Stateless Codec Control ID > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - > =C2=A0=C2=A0=C2=A0=C2=A0 * - ``V4L2_H264_DECODE_PARAM_FLAG_PFRAME`` > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - 0x00000008 > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - All submitted slices for the frame are = P slices. This is a compability > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 flag required for decoders th= at only support decoding such frames, but > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 should not be required for sl= ice-based decoders. Seems to match the comment in Tegra driver, and related to a hardware limitation. Shall we also recommend not to use this unless similar limitati= on exists ? Note that mix of P and I, or, B and I, should still work on Tegra, its mixi= ng P and B that will fail since one of the reference list will be missing. At le= ast, this is my understanding. Nicolas > =C2=A0=C2=A0=C2=A0=C2=A0 * - ``V4L2_H264_DECODE_PARAM_FLAG_BFRAME`` > =C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - 0x00000010 > -=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 - All submitted slices for the frame are = B slices. This is a compability > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 flag required for decoders th= at only support decoding such frames, but > +=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0=C2=A0 should not be required for sl= ice-based decoders. > =C2=A0 > =C2=A0.. raw:: latex > =C2=A0 --=-lValZJkHsUrv43G3L0AC Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iHUEABYKAB0WIQTvDVKBFcTDwhoEbxLZQZRRKWBy9AUCaLC/OQAKCRDZQZRRKWBy 9JjtAQCT0AE/Vs9U8O+KaUh1qw6aB8BbYFDjkxOlrZZk25FPpQD/XVEZOc1kVdFy NsYX7DCRZJ7PzA3mkDkhUEzEMotq5gw= =4NKf -----END PGP SIGNATURE----- --=-lValZJkHsUrv43G3L0AC--