Sunxi NV12 detiling

[Giulio Benetti]

Hi Nicolas, All,

On 17/12/21 16:58, Nicolas Dufresne via gstreamer-devel wrote:
> Le vendredi 17 décembre 2021 à 13:31 +0100, Giulio Benetti via gstreamer-devel a
> écrit :
>> Hello Nicolas, All,
>>
>> I'm dealing with Cedrus on Linux 5.15.7 with Gstreamer 1.19.3.1-git(the
>> latest main branch) and I've got to the point that on A13 and A20 I have
> 
> A bit unrelated I suppose, but I have been blocked on the subject since the
> decoder only produces green frames for me (I have a Lime2 A20 to test this). If
> you could share your kernel branch, and the board DT that works, I could
> possibly try and find the difference and unblock this work on my side.
> 
>> to detile the output of Sunxi video-engine, since now it's done in
>> software and this causes:
>> ```
>> videodecoder
>> gstvideodecoder.c:3670:gst_video_decoder_clip_and_push_buf:<v4l2slh264dec0>
>> Dropping frame due to QoS.
>> ```
>> using kmssink. And I get an entire frame every 5 seconds.
> 
> Of course all to be expected, the CPUs are not very fast, it is single threaded
> by default (see video convert n-threads property), AND this is non-cached CMA
> memory, so that is bare metal IOs, very very slow.
> 
>>
>> I've found this [1] IRC discussion where you state that kmssink support
>> is missing for GST_VIDEO_FORMAT_NV12_32L32. Basically what I understand
>> is that we need a special treatment for A13 and A20, since from >= A33
>> we have the support for the untiled output(still not tried, but I have
>> to do it with A64).
>>
>> Where can I begin from to implement the kmssink support for detiling?
>> There is something I can imitate?
>> Can you or someone else point me more or less where to start working?
> 
> This is all correct, I have a super old patch here that I started for Exynos 4
> DRM, but never finished it. I supposed there is likely a helper now for
> DrmModeAddFb2 (with modifiers, unless that helpers only exist for the atomic
> API, something on my todo). This should be good hint how to translate these
> formats to DRM+Modifiers.
> 
> https://gitlab.freedesktop.org/ndufresne/gst-plugins-bad/-/commit/ac14733163d770499d834bce12863fe6c4b1570c

Thanks a lot for pointing, now I have a path to follow.
I will get into it on Monday.

Kind regards
-- 
Giulio Benetti
Benetti Engineering sas

>>
>> [1]:
>> https://oftc.irclog.whitequark.org/linux-sunxi/2021-07-13#1626188848-1626188913;
>>
>> Thanks in advance
>> Best regards
>