Some questions about MP3's

[Chu]

Today I took my first long hard look at mp3 encoding, and, well, I?m a bit confused. If anyone could help me with these issues, please speak up!
#1: How good is joint stereo? I tested out a few tracks at 192KB cbr j-stereo and stereo, and I did notice a slight difference on one track, but since it wasn't a blind test it could just be my brain tricking itself. Anyone know how good j-stereo imaging is, or any situations where it is known to be screwed up?

#2: From the advice I?ve been gathering, it seems the best tradeoff between audio quality vs. size is LAME's VBR algorithm, with the floor set at 192 and no ceiling (and no abr set). While this is all well and good, I did some further testing with the floors set at 160 and 128 Kbps also. I noticed that the higher you set the floor, the more likely that LAME will "bump" up frames i.e. you have significantly more frames being encoded at 320Kbps with the floor at 190 then the floor at 128 (with a constant quality value at 2). Is there a good reason for this?

#3: I would think that stereo would have a higher average bit rate then j-stereo since I have two separate channels, and thus much more duplicate information, but the file sizes come out almost exactly the same. What is going on here?

I guess the above 3 questions could be summarized by "what exactly is j-stereo doing to my audio?"

#3: If I could, the setting that I think would be best would be true stereo, VBR, floor at 192 and no ceiling. Anyone knows how to set something up like this in EAC? I know all the flags I need to put in there to get this outcome, but I don't know how to tell EAC "stick the filename here" and such.

Anyways, thanks for the advice, and if anyone else has some pointers i'd love to hear them.

-Chu

P.S., I know this is probably not the best place to ask this, but it was the first place that came into mind. Anyone know of a more appropriate forum?

BTW, the settings I?m currently using are j-stereo, 192K floor, no ceiling. Even though I know this is not optimum, since I?m willing to sacrifice more space for true stereo if it is worth it, is there anything particularly wrong with this setup?

 

[Carceri]

While I can't remember the exact difference between j-stereo and stereo (I can find it though) I don't believe that you need to set the floor this high. The file size will be smaller if you set it lower as you yourself has indicated, and I can't tell the difference between having the floor at 96 or 192 (but why encode near silence at 192 if you don't have to).

This site has some information about these things, especially regarding lame.

 

[DieHardware]

I've got a good set of Sony headphones(cost more than $300Cdn. 8 years ago) and I find it hard to hear the difference between 128kbps and 320kbps-but maybe that is do to all the loud concerts I went to as a teenager-PF rullzzzssss . Just remember that MPEG1 level three isn't the be all end all of codecs, there are other good sounding alternatives-JMO.

 

[anthrax]

It really depend what you are listening too really.......in some music types of music there is a noticible difference between 128 and 320

 

[Radboy]

i recently participated in an blind archival listening test at the r3mix forum (see here), with 40 other pairs of ears, using 8 different encoded files.

i have good equipment (sennheiser headphones, 24-bit sound card). what I took from this test is that the best lossy settings for me are either of these two presets:

--dm-preset standard
--dm-preset xtreme

Standard = --nspsytune -V2 -mj -h --lowpass 19.5 -b112 --nssafejoint --athtype 4 --dm-highfreq 3
Xtreme = --nspsytune -V2 -mj -h --lowpass 19.5 -b112 --nssafejoint --athtype 2 --dm-highfreq 3

you need Lame v390 or later to use these. they were noticeably better than the other settings use in the test (except for the super high bitrate mpc file). you may find this helpful.

there's also a good forum here (project mayhem).