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[109.252.159.193]) by smtp.googlemail.com with ESMTPSA id 2adb3069b0e04-55f677491f3sm1370847e87.58.2025.08.30.04.29.49 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Sat, 30 Aug 2025 04:29:50 -0700 (PDT) Message-ID: <11ea89d2-e4f1-4c3a-a2c7-f99170781fba@gmail.com> Date: Sat, 30 Aug 2025 14:29:48 +0300 Precedence: bulk X-Mailing-List: linux-media@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 4/4] Documentation: media: Document V4L2_H264_DECODE_PARAM_FLAG_PFRAME/BFRAME To: Paul Kocialkowski , Nicolas Dufresne Cc: linux-media@vger.kernel.org, linux-kernel@vger.kernel.org, Mauro Carvalho Chehab , Hans Verkuil , Laurent Pinchart References: <20250824180735.765587-1-paulk@sys-base.io> <20250824180735.765587-5-paulk@sys-base.io> <5065e67544ae9255b2136a6cd73cbb9ffd08e3fb.camel@collabora.com> Content-Language: en-US From: Dmitry Osipenko In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 29.08.2025 17:15, Paul Kocialkowski пишет: >>> +      - All submitted slices for the frame are P slices. This is a compability >>> +        flag required for decoders that only support decoding such frames, but >>> +        should not be required for slice-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 limitation >> exists ? > I think the flag should only be allowed for frame-based decode mode and indeed > it would be good to say that drivers should only check this flag if they have > such limitations. > > Userspace on the other hand cannot really know if it will be used or not so it > should set the flags when applicable. IIRC, Tegra dec driver doesn't support decoding frames consisting of multiple slices, it can only decode frames consisting of a single slice. Tegra dec can handle multi-slice frames using a "macroblock by macroblock" decoding mode with a lot of CPU processing, like classic old hw decoders did it, this is not supported by upstream driver.