AW: [vorbis-dev] PlusV algorithm -> CBR

[Segher Boessenkool]

Hannes wrote:
> 
> I don't know if you actually know what vorbis is capable of in respect of
> realtime internet streaming, but you are really *only* missing a correct CBR
> to put you in front of the race.

Bzzzt.  You mentioned the "internet" word.  CBR isn't more useful for internet
transport than (constrained) VBR is.

> Vorbis is a really great codec - I value it
> over most of the available codecs at the moment - but it is a shame that you
> simply cannot rely on some modes when you are intending to send your stream
> over e.g. a modem line.

Modems haven't been CBR for at least a decade now.

> I know it would mean a great deal of damage to vorbis quality, but would it
> really be so bad considering the possibilities? And if, how big would the
> bandwidth adaptation window really have to be - 2 seconds? thats about 1.9
> seconds too long, if this adds on my streaming latency, sorry.

MPEG audio other than Layer I has a >100ms latency, too.

> I mean not to upset you because I know it doesn't work like this if you want
> vorbis quality - but isn't there some kind of compromise? The reason I'm
> writing you is that we are using vorbis as one of our codecs for an internet
> radio demonstrator. We would like to use the 45kbit/s-mode for HiFi-Stereo
> over ISDN (with all 20%FEC and Headers it normally sums up to 60-62 kbit/s).

Bzzzt.  ISDN with PPP isn't CBR.  If you are serious about CBR and low latency,
you want a direct ISDN link (without TCP/IP or whatever, just the raw B pipes)
to your customer.  And your telco operator had better not put some buffering
switch inbetween!

> Sadly the 45kbit/s-mode sometimes behaves like a 64kbit/s vorbis, meaning
> that for a lot of slow, montone passages it really keeps its speed limit,
> but if the going gets rough, bandwidth goes up. This made us decide to use
> the 32kbit/s-mono-setting, which is kind of sad, really.

So what you really want is a setting that will keep the peaks down a little
more.  Maybe someone here can tell you what such a setting should look like?

<p>Segher

<p>--- >8 ----
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