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Date:      Fri, 29 Mar 2002 22:38:57 +0100
From:      Rahul Siddharthan <rsidd@lpt.ens.fr>
To:        "Adam D. Gorski" <agorski@engin.umich.edu>
Cc:        freebsd-multimedia@FreeBSD.ORG
Subject:   Re: SB problem (was: Cat'ing /dev/audio)
Message-ID:  <20020329213857.GB824@lpt.ens.fr>
In-Reply-To: <20020329211628.GA824@lpt.ens.fr>
References:  <20020329191527.B77860@lpt.ens.fr> <Pine.SOL.4.33.0203291602460.8412-100000@and.engin.umich.edu> <20020329211628.GA824@lpt.ens.fr>

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I wrote:

> > Oh, almost forgot.. when I play that 128bps/44Khz Ogg in XMMS, the bitrate
> > fluctuates.. meaning it goes from like 98 to 114 to 104 to 112 and so forth,
> > which is accompanied by the screeching.
> 
> That's a red herring, it doesn't mean anything.  The bit rate isn't
> the sampling rate; the sampling rate is the "output" and is constant,
> the bit rate is the effective number of bits per second in the encoded
> file and can vary according to what compression scheme you're using.  

Or rather, I guess it does mean something but it's not important.
Basically the bit rate is set by the sort of signal at that point of
time; increase in bit rate implies a more complex waveform, which
implies presence of higher frequencies, which implies aliasing problems
in downsampling, which give you your noise...

That is, the bitrate fluctuations don't cause the noise, they're both
caused by certain features in your original sound file.  At least,
that's how it looks to me from here...

Rahul

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