[vorbis] just an idea about quality evaluation

[Daniel Schregenberger]

 ('binary' encoding is not supported, stored as-is)
gtgbr at gmx.net wrote:

> Daniel Schregenberger wrote:
> > > If you're not comparing how the codecs sound (which most people are
> > > interested in), but what data they throw away, this test is very
> > > valuable.
> > So I was essentially right: it may be a help to choose a decent quality
setting
> > for converting mp3s to ogg. (I mean: I can't hear a difference between a
> > 256k_mp3-->q10 and a 256k_mp3-->q9; maybe looking at how much data has been
> > discarded helps me choose a quality)
> 
> Uh ... so you're telling that you make your MP3 files bigger by
> converting them to .ogg @ -q 9 or 10 ??

No. I just chose such high values to make sure everyone gets the point, that I
can't use my ears to hear a difference. I'd probably do the comparison for a
big amount of qualities once, to find a setting I like. I'll post the result
here if I ever get the time to actually do it.

> That's the point of doing that again? Unless you stream in Ogg Vorbis at
> such insane bitrates, which I find unlikely, you're just wasting space
> and quality. Whatever little amount of percievable information Vorbis
> throws away at -q 10, it's still that little info *plus* whatever MP3
> threw away, compared to the original. I also don't know of any player
> that supports .ogg but NOT .mp3, so why re-encode?

I know transcoding is BAD idea. Altough I keep thinking it could work for high
bitrates. At least for me. It's proven by various tests, that almost nobody
hears a difference with 256k-mp3s, including me.
I think about transcoding highbitrate mp3s, cause I like vorbis more,
especially some features like peeling (which will become important to me when I
finally can buy a portable player). Right now I'm just thinking about it. I'll
only do it if I'm sure the additional loss in quality doesn't matter for my
ears.

> Rip again, from CD to .ogg, and you'll be happy with -q 6, 5 or 4, or
> maybe even lower. There's no reason to listen to MP3 quality in .ogg
> files.

Maybe I do not own the CD...and this doesn't have to be in an illegal way: I
could have downloaded it from an official page (band, record-label, ...) or
ripped it from a friends CD (this is legal, at least where I live). If I own
the CD sure: I WILL re-encode, no question.

> And no, you're not right - everybody just said that this kind of
> comparison is completely useless for quality considerations ... I gotta
> know, I asked that question somewhen between 1 to 2 years ago on #vorbis
> and got the same answer - even from Monty himself. :P

Well this was my question. If you tell it wont work, I believe you. I'll maybe
try it nevertheless, just out of curiosity. I need to run against the wall
myself to believe it is there. ;) This is probably an interesting thing where I
could try/use my newly learned NSR skills.

-- Daniel
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