[vorbis] APPLAUD.WAV problems

[Gian-Carlo Pascutto]

----- Original Message -----
From: "Bostjan" <00 at email.si>
To: "_Ogg" <vorbis at xiph.org>
Sent: Thursday, February 14, 2002 6:23 PM
Subject: Re: [vorbis] APPLAUD.WAV problems

<p>> <<<<<<<<
> ----- Original Message -----
> From: "Gian-Carlo Pascutto" <gcp at sjeng.org>
> To: <vorbis at xiph.org>
> Sent: Thursday, February 14, 2002 5:01 PM
> Subject: Re: [vorbis] APPLAUD.WAV problems
> > The ironic fact is that Gian-Carlo seems to have noticed this
> > lossy-stereo-coding problem already and has tuned his OGG encoders to
> > eliminate it.
> I didn't eliminate the lossy-stereo-coding problem; I eliminated the
> lossy stereo modes :)
> >>>>>>>>
>
> It isn't at all a bad idea. Is it possible to add a switch to oggenc that
> eliminates the lossy stereo modes?

It's possible and I presume it will be added in one of the next versions.

Personally, I am _against_ this idea. The advantages
and disadvantages of allowing the user to control the coupling have
been discussed before, and you should be able to dig them up via
the archives.

> <<<<<<<
> Then again, applaud is a known problem
> case for encoders, and it might just as well be the encoder is doing
> things perfectly everywhere else. I don't really like getting impressions
> by using that kind of clips, as I think they are giving a skewed view.
> >>>>>>>>
>
> I agree, but many songs contain applauds and a premium encoder such as OGG
> shouldn't produce such CLEARLY EVIDENT artifacts.

There is nothing that says that Ogg currently fails on all applaud sounds.
Moreover, it handles it fine with a higher quality setting, and I would
imagine
that the applaud sounds are not exactly the ones where good reproduction
is of the utmost importance!

This is a minor problem that can likely be tuned out. It's not the end of
the world.

> You are right. But if a person hears such an evident artefact on a common
> sound like an applaud, he would think again before re-using the encoder
> below -q 5.

Not necessarily a bad thing. Expecting transparency at sub-150 bitrates
is daydreaming, no matter what codec you use. I would be pretty happy
if we can get transparency(*) at around 170kbps!

> <<<<<<
> I'm not trying to downplay that RC3 might have problems on applaud,
> I'm just writing this overly long mail because yours left (at least for
me)
> the impression that GT2 at 160kbps gives better results than RC3 -q5.
> I certainly doub't that is true for the general case, see my answer to
> the next question.
> >>>>>>
>
> I'm sorry to have created confusion. What I actually ment was that GT2 -b
> 128 compresses APPLAUD.WAV better than RC3 oggenc -q 4.9 at the same
> bitrate.

Okay, then this is very likely a stereo coupling problem...GT2 at 128kbps
is essentially RC2 with lossless channel coupling.

> Thank you for you effort. I really enjoy using OGG and I often reccomend
it
> to my friends. I posted this just to report a flaw and help OGG become
> better.

You're welcome, thanks!

(*) this is tricky thing to define. When I talk about it I essentially mean
'good
enough so that even trained listeners will have trouble coming up with a
clip
they can ABX'


--
GCP

<p>--- >8 ----
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