> > I have briefly tried the "--voice" mode and the "normal" mode when
> > encoding a purely voice signal (with background noise) at 8kbps, and
> > have been very impressed with the difference. I would like to compress
> > the signal more... but 8 is as low as it goes.
> >
> > The "nomal" mode renders the voice absolutely unintelligible (I assume
> > the encoder tries too hard to preserve the background).
> >
> > The "--voice" mode actually seems to reduce the background garbage
> > (noise) where there is no speech, and to also concentrate on the
> > speech when it is present.
the voice mode applies a lowpass filter at 12 kHz
> > I have looked at the spectrogram for each, and there is a BIG
> > difference.
and does not use short blocks
> > My question (after all this guff) is "does LAME perform any smarts
> > (like looking for particular frequency domain patterns), and if so,
> > what?"
no, LAME does nothing special for voice signals automagically
> > I have read most of the past articles on "--voice" but they don't tell
> > me all I wish to know. I am also starting with a 11K/samples per sec
> > file (mono) and having to up-sample it to 44.1K before I can process
> > it. Has anyone considered allowing different input sample rates
> > (ie: the standard 16, 22.05, 24, 32, 48) as well as 44.1 ?
you don't need to up-sample your waves.
valid output samplerates are 8, 11.025, 12, 16, 22.05, 24, 32, 44.1, 48
kHz
> >
>
> I first wrote the voice mode, mainly by using some supposition about the
> signal and a lot of listening tests. You can read what was done at the
> beginning by this option here:
> http://www.multimania.com/bouvigne/lame/voice.html
> Because of a lack of time, and the lack of good filtereing solution at
> this time in Lame, I only tuned it for 44.1kHz files.
One point has changed since we have *good filters* in LAME, the highpass
filtering had to be dropped for the voice mode, because the filters are
too rough.
> But now, Robert introduced the presets in Lame, including --preset
> voice, and Lame got some good filters.
> So I think that "--preset voice" is now doing the same thing as --voice,
> and can be used for any sampling rate,
> but I'd like Robert confirmation to know if the behaviour is the same
> as --voice.
No, the voice preset and the voice option are not 100% identical.
By the way, the --voice option is a shortcut for "--lowpass 12 --noshort".
I would suggest looking at "lame --preset help" and experimenting with
--preset phone / --preset sw etc.
> If it's doing the same, I'd suggest you to stop using --voice and start
> using --preset voice instead.
> I personnaly think that now the --voice switch should be removed, as
> there is --preset voice.
I think we should keep it :-)
>
>
> Regards,
> --
>
> Gabriel Bouvigne - France
> [EMAIL PROTECTED]
> icq: 12138873
>
> MP3' Tech: www.mp3-tech.org
Ciao Robert
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