[icecast] Transcoding Ogg streams?

Leo Currie
Fri, 06 Aug 2004 14:23:06 -0000

Hi.

I'm confused about one of the statements on
http://www.vorbis.com/faq.psp#unique

I have a server using Ices2 as the source. I provide it with Ogg's
encoded at quality 5, and I get it to provide lower bitrate streams like
so:
ices.xml
--snip--
<instance>
--snip--
        <encode>
                <samplerate>44100</samplerate>
                <channels>2</channels>
                <quality>0</quality>
        </encode>
</instance>
--snip--
<instance>
--snip--
        <encode>
                <samplerate>22000</samplerate>
                <channels>1</channels>
                <managed>1</managed>
                <nominal-bitrate>20000</nominal-bitrate>

etc etc...
And it works fine.

My question is this:
 From the link above, it says:
"Vorbis has bitrate scaling - a feature that lets you adjust the bitrate
of a Vorbis file or stream without reencoding"
Does this mean that Ices is _not_ re-encoding the vorbis stream, but
actually just magically adjusting it's bitrate?
Or is it just doing ogg->pcm->ogg like I thought it would?
If that is the case, is there a less-processor intensive way of
'transcoding' and ogg stream? Ices seems to use a lot of processor doing
what I have above.

Thanks

Leo