[vorbis] masking problems in Vorbis beta?

[Thomas Marshall Eubanks]

Hello;

Bill Pringlemeir wrote:

> This page contains details of his analysis.
>
>  "http://users.belgacom.net/gc247244/analysis.htm"
>
> Look at the `original signal' line to explain the low frequency cut
> off in the ogg analysis.
>
>  "http://users.belgacom.net/gc247244/ns-ogg.png"
>
> Frequencies above 16 kHz and hard for most people to hear.  I don't
> really think that it matters for human ears.  These test are the type
> that anal retentive audiophile weenies like to do.

FM radio, in the US at least, only goes up to 16 kHz. I have therefore listened to a lot of
music with a 16kHz upper limit (i.e., in my car), and generally it sounds fine.
I think it is dangerous, however, to make blanket generalizations. In any lossy compression scheme,
the real question has to be, "How often do you want it not to sound right ?", and
the frequent silibence in MP3 encoded music may be related to insufficent bandwidth
to enode the high frequencies adequately.

>
>
> Examine his critic of the MP3 encoders.  His best test is with an
> actual song.  Although I would think that Ogg Vorbis would do better at
> pure tones, since it uses MDCT.  This is somewhat distressing to me.

The test is somewhat artificial, but ...

A few days ago on the list, someone asked for a mathematical description of the
Vorbis compression scheme. I did not see a response. Without knowing this, it is hard
to know how to interpret these tests.

>
>
> The last thing to note is the human ear hears in a logarithm mode.
> All of his graphs are linear, which can make things look worse than
> they are, 3 or 6 db is not much of a difference.

I don't understand this - his plots are in deciBels (dB), which is a log scale.

>
>
> Maybe someone else can provide better details; I am certainly not
> an insider. `Ich Bin Ein Auslander'
>
> Bill
>
> >>>>> "Martin" == Martin Reinecke <martin at MPA-Garching.MPG.DE> writes:


--
                                 Regards
                                 Marshall Eubanks

T.M. Eubanks
Multicast Technologies, Inc
10301 Democracy Lane, Suite 410
Fairfax, Virginia 22030
Phone : 703-293-9624
Fax     : 703-293-9609
e-mail : tme at on-the-i.com     tme at multicasttech.com

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