[vorbis] Difficult sample for vorbis w/ audible artifacts

[Darin Morrison]

> I grabbed the WAV, and encoded it with the latest Oggdrop at 350kbps. I
> dragged 5 instances of the WAV file, and 5 instances of the Ogg file into
a
> Winamp playlist, and randomized it. I don't hear any artifacts in the Ogg
> file..
> Next, I encoded the WAV file to a 128kbit VBR MP3 with RazorLame, and into
a
> 128kbit Ogg file with Oggdrop 1.0b4. I put three instances of each into a
> Winamp playlist, and 3 instances of the WAV file. Hit randomize, turned up
> the volume, closed my eyes, hit play. I really don't hear any artifacts.
> Admittedly, I'm using Klipsch Promedia 4.1s.. Not reference quality stuff.
I
> left my Sennheisers at work today.. I get the impression from your message
> that it's not supposed to be that subtle.
> If it would help, I could make my mp3 and ogg test tracks available to
you..
>

I should have probably clarified this in the original message, but the
artifacts in question are harder to hear on a stereo system than on
headphones.  I don't have the best set of headphones (Sony MDR-V600's, plan
on getting some Sennheisers or Grado's soon) but I can hear them very
clearly.  I do have a harder time hearing them, at least with vorbis, on my
midrange Sirocco Pro system though but there's no question they are
definitely there. I could pick the vorbis encoded samples out of an abx test
16/16 times with absolutely no problem.  If you follow the last link in my
original message there's quite a bit of discussion about the artifact
already, I'd rather not retype everything I already have.  Here's the meat
of it at least:

"Just tested the clip with vorbis beta4.  Heres what I found.

This clip tested initially with oggenc -b 256 (~226) sounds *much* better
than LAME/--r3mix.  I was actually quite surprised.  Almost all of the
annoying errors are gone.  However, I did try listening with an abx test and
I was able to pick it 16 out of 16 times.  There seems to be another
artifact with vorbis that I don't hear with --r3mix.  Right at the end of
the bass note, or "fart" as ff123 put it, there is a little humming sound..
like a bit of added resonance or something.  It took me a few tries to
distinguish it but once I had I was able to pick it out of the abx every
single time.  In my opinion though this is a far less annoying artifact than
with LAME.

I also tried with oggenc -b 180 (~186) to be more "fair" to --r3mix.  It
actually sounds quite a bit worse than with -b 256.  The bass note is alot
"noisier" and there is a very obvious pre-echo during the start of the "zip"
sounds.  However, with both settings with vorbis, I don't hear the tapping
sounds overlaid upon the "zips" like I do with mp3.  The attacks don't seem
as sharp as the .wav or with mpc still though"

Anyway, I could understand maybe not hearing the distortion on the bass
note, but the pre-echo artifact, especially at lower bitrates, is very
obvious.

Dibrom

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