[vorbis-dev] Sample still has horrorible distortions... anyone know why?

[Bruno Barreto]

----- Original Message -----
From: Monty <xiphmont at xiph.org>
To: <vorbis-dev at xiph.org>
Sent: Monday, November 20, 2000 5:28 AM
Subject: Re: [vorbis-dev] Sample still has horrorible distortions... anyone
know why?

>
> Ah, OK, just rechecked these with graphing instead of only listening.
>
> Sweep.wav freaked me out at first because I *have* that sample, and it
> was perfect...  It turns out ours are different in that mine is
> attenuated -2dB.
>
> On sweep.wav your problem is clipping.  Vorbis is psychoacoustic only
> and the psychoacoustic engine doesn't know where the 'rails' are.
> You're feeding in a sample that's going full range all the time, and
> Vorbis is replicating it to within .5-1 dB... which according to its
> calculations is enough.  Unfortunately, that is causing clipping which
> looks and sounds pretty bad.  Attenuate your sample slightly and
> you'll see the problem go away.

I'll try that, thanks :)

>
> Mechanisms for backfilling more resolution/attenuating the waveform in
> this case won't be in place until beta 4.

I'll be waiting and i'll try oggenc against this same sample when b4 is
released then.

> Velvet.wav: This sample is hard because it requires short blocks where
> there's a heavy bassline but little/no lower midrange masking.  In
> short blocks, bin 0 represents roughly 0-350 Hz (almost five octaves!)
> and thus can require an absurd level of precision where the DC offset
> is large, but there's no midrange to mask frame boundaries.  Beta 3
> does not yet have the mechanism to fill the required bits in.  (It
> should still be *much* better than beta 2, but I know it's not yet
> perfect).
>
> Monty

I still hear artifacts but yes it sounds better...

btw; sorry everyone! I noticed i flooded the mailing list with my emails...
It's just that my ISP's smtp server is new and thus is being tested.
Sometimes i send msgs and they don't reach their destination. So when i sent
the 2nd msg it took a looong time to return to me, and i thought it'd been
lost thus sent it again... Sorry..! :)

>
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