linux-kernel - Re: [PATCH v5 2/4] staging: media: Introduce NVIDIA Tegra video decoder driver

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Date:   Mon, 23 Nov 2020 14:09:20 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Stephen Warren <swarren@...dotorg.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hverkuil@...all.nl>,
        Vladimir Zapolskiy <vz@...ia.com>,
        Rob Herring <robh+dt@...nel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        linux-media <linux-media@...r.kernel.org>,
        devel@...verdev.osuosl.org,
        devicetree <devicetree@...r.kernel.org>,
        linux-tegra@...r.kernel.org,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Nicolas Dufresne <nicolas.dufresne@...labora.com>
Subject: Re: [PATCH v5 2/4] staging: media: Introduce NVIDIA Tegra video
 decoder driver

23.11.2020 06:07, Ezequiel Garcia пишет:
> On Sat, 21 Nov 2020 at 23:01, Dmitry Osipenko <digetx@...il.com> wrote:
>>
>> 22.11.2020 04:02, Ezequiel Garcia пишет:
>>> Hi Dmitry,
>>>
>> ...
>>>> +++ b/drivers/staging/media/tegra-vde/TODO
>>>> @@ -0,0 +1,4 @@
>>>> +TODO:
>>>> +       - Implement V4L2 API once it gains support for stateless decoders.
>>>> +
>>>> +Contact: Dmitry Osipenko <digetx@...il.com>
>>>
>>> The API for H264 stateless decoding is ready.
>>> See https://lkml.org/lkml/2020/11/18/795.
>>
>> Hello Ezequiel,
>>
>> Thank you for the notification! My last attempt at implementing V4L API
>> support was about a year ago and it stopped once I realized that there
>> is no userspace which uses that API. FFMPEG and chromium browser had
>> some kind of V4L support, but it all was oriented at downstream driver
>> stacks, and thus, not usable. Do you know what is the current status?
>>
> 
> The bulk of the API, which relies on the stateless decoder interface [1],
> and H264 stateless V4L2 controls has been ready for some time now,
> and there are various implementations supporting it.
> 
> Chromium supports it [2], and I've tested it on chromebooks,
> through chromeos builds. We haven't tried a non-chromeos build,
> and I would say it's quite some work.
> 
> GStreamer support is available as well. See [3] which should
> work for the latest H264 controls (the ones being moved out of staging).
> 
> LibreELEC developers maintain an Ffmpeg branch [4], I expect it will
> be updated for the latest H264 controls soon, and hopefully merged
> in mainline Ffmpeg.
> 
> GStreamer and Ffmpeg are relatively straightforward to build and test.
> 
> Thanks,
> Ezequiel
> 
> [1] https://www.kernel.org/doc/html/latest/userspace-api/media/v4l/dev-stateless-decoder.html
> [2] https://github.com/chromium/chromium/tree/master/media/gpu/v4l2
> [3] https://gitlab.freedesktop.org/ezequielgarcia/gst-plugins-bad/-/tree/h264_stable_uapi
> [4] https://github.com/Kwiboo/FFmpeg/tree/v4l2-request-hwaccel-4.3.

Alright, thank you.