(jweeks @ Jun 18 2003 - 09:36 PM)

From reading this thread:

http://discussions.info.apple.com/WebX?128...Hk.18@.3bc2a4c8

...it appears that iTunes 4.0.1 uses the "BETTER" QT quality (not "BEST") -- it sacrifices quality for higher encoding speed.

Strange, my encoding speed dropped dramatically with the 4.01 upgrade. I wonder if Good is like q3 for lame, better is like q2 and best is like q0.

iTunes does use the SAME encoder as QT, and iTunes does give the user the ability to change the encoder's mode. iTunes uses the "Better" quality mode (not the fastest) which is optimized to perform best with 16bit source material (ie. CD source). "Best" quality mode is targetted at 24bit source material (eg. DVD source) and there should be NO discernible difference in quality for CD source between these two modes of the encoder. Generally it's just a waste of CPU to use best quality for 16 bit source, but there's no harm done by doing this of course.

Roberto, do you still plan on adding the individual user comments and sample bitrates?

I've been having a very fruitful e-mail swap with Apple's head AAC developer,  Mr. Stanley Kuo. Here's his clarification on this specific subject:


QUOTE

iTunes does use the SAME encoder as QT, and iTunes does give the user the ability to change the encoder's mode. iTunes uses the "Better" quality mode (not the fastest) which is optimized to perform best with 16bit source material (ie. CD source). "Best" quality mode is targetted at 24bit source material (eg. DVD source) and there should be NO discernible difference in quality for CD source between these two modes of the encoder. Generally it's just a waste of CPU to use best quality for 16 bit source, but there's no harm done by doing this of course.

But, where is iTunes' option to "give the user the ability to change the encoder's mode"?  I can't find it...

Funny that everybody hears different things.

One of the codecs got these comments but was still ranked second for this sample... the others must sound horrible then.

"Bad pre-echo, clicks, cut-off, warble, 'discrete' freq sweep, dirtier, noisy, tones merging, distortion or clipping, noisy attacks, rumbling, muffled, post echo tones, smeared attacks, faser sound, gurgling, noisy hi-hats"

I'm quite surprised, for this. I remember a previous thread where Ivan Dimkovic stated this codec (AACdemo) "as the state of art" around 128 kbps. But i'm not here to start a flame, i respect the other's impressions and the tests conclusions.

I see a couple of results that confuse me:

1)

http://rarewares.hydrogenaudio.org/test/aa...Z-results03.txt

The rating is 5.0.  How is this possible?  ABC/HR should not have recorded a value of 5.0, or is there some sort of bug somewhere?

2)

http://rarewares.hydrogenaudio.org/test/aa...alf_results.txt
http://rarewares.hydrogenaudio.org/test/aa...alf_results.txt

Hopefully, the two separate ratings were combined afterwards by the listener to yield a composite rating.

,Jun 22 2003 - 11:34 AM] @Roberto: What about to publish anymously the scores for those people who don't want to be named ?
I think that the raw scores and the comments (with or without names) should be published. IIRC this was the method adopted by ff123 for the 64 kbps test.

If you want to allow me to publish your comments and/or scores,
  please make that clear in the e-mail body. If there's no
  mention of it, I WILL NOT publish the comments, and the scores
  will only be mentioned in the final results, anonimously.

Man, Gecko tossed all the codecs into the rubbish bin!  I wish I had spread my scores out, to better differentiate the scores and make my results a bit more statistically significant.

Here's another discrepant result:

http://rarewares.hydrogenaudio.org/test/aa...Z-results08.txt

The 3L on the left of the bottom portion doesn't match up with the name of the file on the top portion.  Again, a rating of 5.0 was assigned.

ff123

Ah. Duh. That one was me. So that your process program would add all the 5.0 results to the list and not output errors to the listing file.

I will revert the mess uploading the original results files (empty) that he sent me.

In general, the lower a listener scored, the more sensitive he must be to artifacting.  Of course, people don't necessarily use the same part of the rating scale -- that's why I said the index is crude.