linux-kernel - Re: i.MX6 CSC and scaler

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Date:	Tue, 16 Dec 2014 14:30:35 +0100
From:	Philipp Zabel <p.zabel@...gutronix.de>
To:	Jean-Michel Hautbois <jean-michel.hautbois@...alys.com>
Cc:	Nicolas Dufresne <nicolas.dufresne@...labora.com>,
	Steve Longerbeam <slongerbeam@...il.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Frédéric Sureau 
	<frederic.sureau@...alys.com>,
	Fabio Estevam <fabio.estevam@...escale.com>
Subject: Re: i.MX6 CSC and scaler

Am Montag, den 15.12.2014, 22:27 +0100 schrieb Jean-Michel Hautbois:
> 2014-12-15 19:52 GMT+01:00 Nicolas Dufresne <nicolas.dufresne@...labora.com>:
> > Le 12/15/2014 01:23 PM, Steve Longerbeam a écrit :
> >> You would need to write a gstreamer plugin to make use of the
> >> mem2mem device for h/w CSC and scaling.
> 
> Thank you Steve, this is of a great help !
> 
> > There is an element already (v4l2transform), though it currently only
> > handle color conversion. I'd like to see scaling in that too instead of
> > having a separate element that only do scaling like:
> >
> > https://bugzilla.gnome.org/show_bug.cgi?id=726104
> 
> Nice idea. You are probably right Nicolas, it would make sense to be
> able to scale and convert color in the same element.
>
> > I think Michael and Philipp idea was that scaling could be done directly
> > out of the decoder, something supported by CODA driver. There is some
> > work require to get that in GStreamer, see:
> >
> > https://bugzilla.gnome.org/show_bug.cgi?id=733827 (pixel format nego)
> > https://bugzilla.gnome.org/show_bug.cgi?id=733828 (display size nego)
> 
> There is a need for a separate element too. So it could be handled in
> front of the encoder if needed, on decoder output if needed, but
> should be a single element too, instanciable multiple times if
> multiple inputs/outputs are needed.

Scaling in the decoder element is desirable, but unrelated. I wanted
that for the CODA JPEG decoder, which can produce decimated output right
during the decoding process.

For the IPU IC mem2mem scaler/CSC, v4l2transform with scaling capability
would be the perfect fit.

regards
Philipp

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