Romain,
You are correct.
Using vorbis.cbr or abr increases CPU load by a lot. Using simply vorbis
vbr (like so: (%vorbis(quality=0.3)), and CPU is nice and cool :)
For mp3, using vbr or cbr does not matter - CPU uses same percentage as
vorbis vbr.
Thanks,
Martin
2012/3/7 Romain Beauxis <[email protected]>
> Hi Martin!
>
> 2012/3/6 Martin Konečný <[email protected]>:
> > I was thinking about this a little more and I guess there is a two stage
> > process?
> >
> >
> > So assuming we have a icecast vorbis output, and we input an mp3, the
> first
> > stage is to convert that mp3 to vorbis.
> >
> > The second stage is to upconvert or downconvert the bitrate according to
> our
> > preference.
> >
> > So when I don't specify the bitrate, the second stage is never run
> resulting
> > in a lower CPU %.
> >
> > If this is correct, than what is the default output bitrate of the first
> > stage?
>
>
>
> All audio data inside liquidsoap is in PCM. This means that mp3 audio
> data is always decoded to PCM and then encoded to vorbis.
>
> As for the default vorbis settings, I agree that the doc is not really
> helpful. %vorbis is by default set to variable 128kbps.
>
> As for the CPU load, I have no clue except that I believe it that it
> comes from libvorbis and that I think that libvorbis was primarily
> designed to do variable bitrate so that maybe constant bitrate is not
> a "natural" operation for libvorbis..
>
> Romain
>
--
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Martin Konecny
Software Developer, Sourcefabric
[email protected]
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Skype: martin.konecny15
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