Date:   Wed, 11 Nov 2020 00:28:03 +0200
From:   Adrian Ratiu <adrian.ratiu@...labora.com>
To:     Ezequiel Garcia <ezequiel@...guardiasur.com.ar>
Cc:     linux-media <linux-media@...r.kernel.org>,
        Mauro Carvalho Chehab <mchehab@...nel.org>,
        Ezequiel Garcia <ezequiel@...labora.com>,
        Boris Brezillon <boris.brezillon@...labora.com>,
        Hans Verkuil <hverkuil-cisco@...all.nl>,
        Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        kernel@...labora.com
Subject: Re: [PATCH v5 0/3] media: rkvdec: Add a VP9 backend

Hi Ezequiel,
 
On Tue, 10 Nov 2020, Ezequiel Garcia 
<ezequiel@...guardiasur.com.ar> wrote:
> On Mon, 2 Nov 2020 at 16:04, Adrian Ratiu 
> <adrian.ratiu@...labora.com> wrote: 
>> 
>> Dear all, 
>> 
>> This is v5 of the series adding VP9 profile 0 decoding to 
>> rkvdec. 
>> 
>> All feedback from v4 should be addressed, there's just one 
>> thing I did not address: ref_frame_sign_biases in the uAPI. The 
>> userspace tool I'm 
> 
> I believe that Hantro G2 VP9 needs ref_frame_sign_biases. 
> 
> I think that it's also needed for the MTK decoder.  Might be 
> worth checking that as well, if the code is publicly available 
> somewhere.

I consulted the imx8m app ref manual for the Hantro G2 core and 
indeed there's not one, but three fields at SWREG11 and 13 (last, 
gold, alt) to signify sign biases for ref frames. Thanks for the 
hint!
 
> 
> Coming to think about it, I think we are really close to having 
> this uAPI directly upstream. 
> 
> Let's take a step back on why we have these uAPIs in the staging 
> area. Couple years ago, there were some doubts in the media 
> community about these uAPIs, and we wanted to wait a bit for 
> more users before moving to public land. 
> 
> The uAPIs were meant to be in staging until enough users 
> appeared and we were confident enough to move to stable. 
> 
> For VP9, given the feedback received through the year was 
> already addressed, I think all that's left is to check the 
> interface and make sure it can support Rockchip (RK3399, RK3326, 
> etc), Hantro G2 and Mediatek, 
> 
> We will be very close to having a public API, and we could even 
> merge it directly there.

Thank you very much for this background. I understand that the 
uAPI is independent from the driver implementations, so having a 
good stable uAPI is beneficial when (for example) adding support 
for VP9 on G2 in  hantro or for upstream adoption of these 
drivers.

Given this rkvdec driver implementation is also adding the VP9 
uAPI and it's very close to stability (maybe only missing ref 
frame sign bias, but who knows?) would you like to block its 
submission until the uAPI is finalized or would it make sense to 
treat the uAPI de-staging process separately because the uAPI is 
independent from the driver? 

Thanks,
Adrian

>
> Thanks,
> Ezequiel
>
>> using [1] apparently doesn't need it or the default hwreg value for it
>> is capable of decoding the bitstreams I used on the driver, so I don't
>> really have a use-case to change and test that. :)
>>
>> Considering the uAPI is a work in progress and expected to be modified,
>> ref_frame_sign_biases can be added later with others which might be
>> required to enable more functionality (for eg profiles >= 1).
>>
>> Series tested on rk3399 and applies on next-20201030.
>>
>> [1] https://github.com/Kwiboo/FFmpeg/tree/v4l2-request-hwaccel-4.2.2-rkvdec
>>
>> Changelog
>> ---------
>>
>> v5:
>>
>> * Drop unnecessary OUTPUT buffer payload set in .buf_prepare.
>> * Drop obsolete .per_request ctrl flag
>> * Added new vp9 ctrls to v4l2_ctrl_ptr
>> * Fix pahole detected padding issues
>> * Send userspace an error if it tries to reconfigure decode resolution
>>   as v4l2 or rkvdec-vp9 backend do not support dynamic res changes yet
>> * Allow frame ctx probability tables to be non-mandatory so users can
>>   set them directly during frame decoding in cases where no defaults
>>   have been set previously (eg. ffmpeg vp9 backend)
>> * Some comments and documentation clarifications
>> * Minor checkpatch fixes
>>
>> v4:
>>
>> * Drop color_space field from the VP9 interface.
>>   V4L2 API should be used for it.
>> * Clarified Segment-ID comments.
>> * Moved motion vector probabilities to a separate
>>   struct.
>>
>> v3:
>>
>> * Fix documentation issues found by Hans.
>> * Fix smatch detected issues as pointed out by Hans.
>> * Added patch to fix wrong bytesused set on .buf_prepare.
>>
>> v2:
>>
>> * Documentation style issues pointed out by Nicolas internally.
>> * s/VP9_PROFILE_MAX/V4L2_VP9_PROFILE_MAX/
>> * Fix wrong kfree(ctx).
>> * constify a couple structs on rkvdec-vp9.c
>>
>>
>> Boris Brezillon (2):
>>   media: uapi: Add VP9 stateless decoder controls
>>   media: rkvdec: Add the VP9 backend
>>
>> Ezequiel Garcia (1):
>>   media: rkvdec: Fix .buf_prepare
>>
>>  .../userspace-api/media/v4l/biblio.rst        |   10 +
>>  .../media/v4l/ext-ctrls-codec.rst             |  550 ++++++
>>  drivers/media/v4l2-core/v4l2-ctrls.c          |  239 +++
>>  drivers/media/v4l2-core/v4l2-ioctl.c          |    1 +
>>  drivers/staging/media/rkvdec/Makefile         |    2 +-
>>  drivers/staging/media/rkvdec/rkvdec-vp9.c     | 1577 +++++++++++++++++
>>  drivers/staging/media/rkvdec/rkvdec.c         |   72 +-
>>  drivers/staging/media/rkvdec/rkvdec.h         |    6 +
>>  include/media/v4l2-ctrls.h                    |    5 +
>>  include/media/vp9-ctrls.h                     |  486 +++++
>>  10 files changed, 2942 insertions(+), 6 deletions(-)
>>  create mode 100644 drivers/staging/media/rkvdec/rkvdec-vp9.c
>>  create mode 100644 include/media/vp9-ctrls.h
>>
>> --
>> 2.29.0
>>

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