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

[Hannes]

Hi,

>> 2) CBR encoding
>
>You can do something close to that already with the bitrate management
>engine, e.g. limit the bandwidth to a certain bitrate within a 2-seconds
>window. An oggenc command line would look like `oggenc --managed -m
><bitrate> -b <bitrate> -M <bitrate> input.wav`. I'm not quite sure why
>you'd want this, though - quality suffers and CBR is only required in
>pretty exotic environments.
>

If you consider a streaming application an exotic environment, OK.
Personally, I don't.

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. 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.

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.

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).
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.

If you are interested, I would gladly set up a server for you so you can see
for yourself - maybe it's our implementation, I would really hope so. The
link so far (binary only in german, sorry):
http://www.igd.fraunhofer.de/~wam  [ don't be afraid of the 'Fraunhofer' ;]

Thanks for your time (and thanks for vorbis, keep up the good work),

Hannes

//
// we apologize for the inconvenience
//
// Hannes Guddat
// Fraunhofer IGD
// A9 - Communication and Cooperation
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