[Jingle] Audio and Video codecs

[Justin Uberti]

Justin K. and I discussed off-list about how a requirement to support a
"baseline" codec could be impossible to satisfy in certain situations (i.e.
a mobile phone which already has a h.264 decoder for video playback, but
cannot absorb the cost of a separate chip for theora processing).
We agreed that getting signaling interop fully speced as part of XEP-0167 is
a big deal, and while it would be great to be able to ensure media interop,
there are practical considerations that make it unrealistic for us to
require that. However, keeping our codec recommendations in XEP-0167 will
force implementors to at least consider the issue.

--justin

On Fri, Jan 30, 2009 at 9:45 PM, Justin Karneges <justin at affinix.com> wrote:

> On Friday 30 January 2009 20:47:47 Olivier Crête wrote:
> > If we want to recommend codecs in the XMPP specs, the only ones I can
> > recommend now are G.711, Speex and Theora. Also, H.261 was standardised
> > in 1990, so it is probably also free of patent claims.
>
> Indeed, and for this reason G.711, Speex, and Theora are already
> recommended
> in XEP-167.
>
> > [snip codec listings]
>
> While there's certainly cool factor in supporting 30 codecs, I don't
> believe
> XMPP clients in general should have a need to do that.  It should be
> possible
> to have 100% compatibility by implementing the minimum required codecs.
>
> Currently, XEP-167 merely recommends 3 codecs.  I'd like to see the
> language
> changed such that Speex and Theora are REQUIRED.
>
> We can keep the G.711 recommendation in there just so there's a good chance
> transcoding won't be needed for PSTN gateways.  To be clear though: an
> XMPP<->PSTN gateway would still need to support transcoding from Speex to
> be
> XMPP compliant, since availability of G.711 wouldn't be guaranteed.
>
> I don't think it's worth recommending a legacy video codec.
>
> If we can agree that Theora should be required, I'd be interested in making
> an
> agreement among XMPP client projects (at least those caring to be
> political)
> to not support any other video codec except for Theora.  I'm mainly
> concerned
> about H.264 ending up de facto, which would be a complete mess.
>
> -Justin
>
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