linux-kernel - Re: [PATCH] media: rkvdec: set ctx->image_fmt in rkvdec_s_capture

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Message-ID: <20251213055942.3046647-1-liujianfeng1994@gmail.com>
Date: Sat, 13 Dec 2025 13:59:42 +0800
From: Jianfeng Liu <liujianfeng1994@...il.com>
To: nicolas.dufresne@...labora.com
Cc: detlev.casanova@...labora.com,
	ezequiel@...guardiasur.com.ar,
	heiko@...ech.de,
	hverkuil@...nel.org,
	jonas@...boo.se,
	linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org,
	linux-media@...r.kernel.org,
	linux-rockchip@...ts.infradead.org,
	liujianfeng1994@...il.com,
	mchehab@...nel.org
Subject: Re: [PATCH] media: rkvdec: set ctx->image_fmt in rkvdec_s_capture_fmt

Hi,

On Fri, 12 Dec 2025 12:53:53 -0500, Nicolas Dufresne wrote:
>I'm reading you here, and reading the spec again [0], and you are saying the
>Chromium isn't following the initialization process. That means, it should be
>impossible to allocate 10bit capture buffer, since the SPS in place specify the
>color depth. Other parameters in other codec can influence the reference buffer
>size, so you could endup with the wrong allocation.

Chromium does follow the spec when decoding 10bit videos[1], but that is
still limited to hevc and vp9. For h264 and 8bit video chromium thinks
this is unnecessary.

>You cannot accept a format that falls against the color depth in the SPS
>control, and rkvdec does not do color conversion implicitly. This can otherwise
>lead to letting the HW overrun the buffer (forcing 8bit with 10bit content). Can
>you check with Chromium dev if they can perhaps adhere to the spec instead ?
>This is all news to me, but I probably never had to test 10bit playback in
>Chromium outside of MTK (which might not be less strict, hopefully done the
>right way).

I will try to fix chromium to follow the spec. Since rkvdec driver is the
only driver related, I didn't check the stateless spec.

[1]https://github.com/chromium/chromium/blob/145.0.7577.2/media/gpu/v4l2/v4l2_video_decoder.cc#L648-L650

Best regards,
Jianfeng