linux-kernel - Re: [PATCH v2 0/7] media: rkvdec: Add HEVC backend

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Message-ID: <816fa42715e8bc4bf538371975f97b6d102a74f5.camel@collabora.com>
Date: Tue, 12 Aug 2025 09:27:58 -0400
From: Nicolas Dufresne <nicolas.dufresne@...labora.com>
To: Diederik de Haas <didi.debian@...ow.org>, Jonas Karlman
 <jonas@...boo.se>,  Ezequiel Garcia <ezequiel@...guardiasur.com.ar>, Detlev
 Casanova <detlev.casanova@...labora.com>, Mauro Carvalho Chehab
 <mchehab@...nel.org>
Cc: Alex Bee <knaerzche@...il.com>, linux-media@...r.kernel.org, 
	linux-rockchip@...ts.infradead.org, devicetree@...r.kernel.org, 
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/7] media: rkvdec: Add HEVC backend

Le mardi 12 août 2025 à 14:55 +0200, Diederik de Haas a écrit :
> Hi again,
> 
> On Tue Aug 12, 2025 at 2:11 PM CEST, Diederik de Haas wrote:
> > On Sun Aug 10, 2025 at 11:24 PM CEST, Jonas Karlman wrote:
> > > This series add a HEVC backend to the Rockchip Video Decoder driver.
> > > 
> > > Patch 1 add the new HEVC backend.
> > > Patch 2-3 add variants support to the driver.
> > > Patch 4 add support for a rk3288 variant.
> > > Patch 5 add a rk3328 variant to work around hw quirks.
> > > Patch 6-7 add device tree node for rk3288.
> > 
> > It looks like I had a previous version of linuxtv-rkvdec-hevc-v2 branch
> > locally and that also had this commit:
> > - media: rkvdec: Keep decoder clocks gated
> > 
> > Is that one no longer needed/useful/etc ?
> > 
> > And 'chewitt' also had a commit to fix 8/10-bit selection:
> > https://github.com/chewitt/linux/commit/4b93b05d2ca608bc23f1d52bcc32df926d435c7c
> > "WIP: media: rkvdec: fix 8-bit/10-bit format selection"
> > 
> > I haven't tried that one (yet), but did  try an other variant with
> > changing the ordering in rkvdec_hevc_decoded_fmts but that didn't work
> > in my tests. (Can ofc be PEBKAC)
> > 
> > Would that be useful? I do/did have consistent problems with playing
> > 10-bit encoded video files.
> 
> nvm about the 10-bit problem. It exists, but it's not restricted to HEVC
> as it also exists with with H.264 files.

The referred patch is against some out-dated kernel. In mainline linux with
have:

	if (sps->bit_depth_luma_minus8 == 0) {
		if (sps->chroma_format_idc == 2)
			return RKVDEC_IMG_FMT_422_8BIT;
		else
			return RKVDEC_IMG_FMT_420_8BIT;
	} else if (sps->bit_depth_luma_minus8 == 2) {
		if (sps->chroma_format_idc == 2)
			return RKVDEC_IMG_FMT_422_10BIT;
		else
			return RKVDEC_IMG_FMT_420_10BIT;
	}

Which covers all cases supporte by the hardware. Chewitt seem to add a
previously missing 10bit case, and forcing downconversion from 422 to 420. A
downconversion is something to be chosen and applied by userspace, the kernel
should pick a non-destructive format by default.

Nicolas

> 
> Cheers,
>   Diederik

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