Re: ABX test invite

[Thomas Vecchione <seablaede@xxxxxxxxx>]

So here is the thing, it makes a large difference what the source is as to how obvious it would be.  Case in point, I found the v6 difficult on the files in the thread, but I toss in one of my recordings(Using lame with v4 and v6 as above) from a live concert and holy crap is there a difference, obvious right from the get go in the hiss in the track on v6.  v4 on the other hand was very difficult to tell on that track to where I don't think I could hear a difference.  But that only makes me wish I had some decent recording of full orchestral classical at my workstation to listen to as that is my goto material for a source.  Or irish folk music, which can do a decent job as well causing problems of more than one sort:)

Some things to keep in mind, I am listening over studio monitors, not headphones, but still much better than the average listening environment.  It would likely be even more obvious over headphones to tell the truth.  Second it always makes a difference in the second generation encoding, which is why I tend to use FLAC for archival and master purposes, and use OGG or otherwise for listening, so that I never risk a second generation compression, which becomes more obvious.

Via abx, there wasn't ever a question with v8 really.  v6 as I mentioned on the sources mentioned above were much harder, but if I tossed in my own acoustic/folk recording it became very blatant.  Again source makes all the difference.  v4 I couldn't tell over speakers, but I also don't have most of my music collection here either, so I really should come back to it with some decent classical and irish folk tracks and see what happens.

        Seablade

On Wed, Apr 3, 2013 at 3:06 PM, Peder Hedlund <peder@xxxxxxxxxxxxxx> wrote:

Quoting Peder Hedlund <peder@xxxxxxxxxxxxxx>:

In view of the recent debate regarding the alledged "crappiness" of MP3
I thought it would be fun to see if the LAU society can tell lame
(v3.99.4) MP3s from the original.

Everyone is invited to download the testfiles from
http://www.musikhuset.org/~peder/AxelF.zip , see if you can ABX them
and post the result.

I actually surprised myself regarding the 124 kbps sample :

trials 10

against 165: correct 5, p-value 0.623

against 124: correct 10, p-value 0.000977
against 108: correct 10, p-value 0.000977

Tested using Sennheiser HD 280 pro headphones.

A hint for testing is to have the sound start playing at 5s and listen to the "warble". At around 8s there's a distinct flaw that also sticks out.

One drawback in using the ABX Tester from http://phintsan.kapsi.fi/abx.html is that it's not double blind since you know which file is A and which is B.
I think the foobar2000 ABX plugin randomizes this at startup.
But then again, once you've figured out what to listen for you hear it pretty much instantly, if you *can* hear it.

- Peder
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