Tee to forward allocation queries (was: Multiple sink usage in im6x)

[Yasushi SHOJI]

Hi Nicolas,

On Wed, Jun 21, 2017 at 12:59 AM, Nicolas Dufresne <nicolas at ndufresne.ca>
wrote:
> Le mardi 20 juin 2017 à 13:21 +0900, Yasushi SHOJI a écrit :
> > the tee element reads FullHD buffer from vpudec to userland, memcpy()
it, and
> > enqueues/writes back to imxv4l2sink and imxeglvivsink.
> >
> > I don't know how those sinks are implemented but it takes some IO and
CPU
> > time for sure.
>
> With tee, the zero-copy options are indeed very limited as tee
> currently drops the allocation queries. We don't know yet how to
> aggregate an allocation query to enable some zero copy with a tee
> (multiplexer).

It's off topic but what was the reason for tee to drop allocation queries?

GstBuffer has read-only shared capability, so it's possible to send the
same buffer
to multiple downstream?

Even with dmabuf support, tee could forward allocation queries and
resulting buffers
back and forth, no?

I'm not familiar with other device specific allocation method, but the
GstBuffer,
in theory, should encapsulate what's underneath right?

I'd appreciate if you'd enlighten me a bit.

Thanks,
-- 
             yashi
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