2 replies to this topic

[nightanole]

Ive been listening to this station for a while. Ive seen the quality walk around from 128k max down to 96k max. Now the new station uses aac. Aac was junk for years (i think it started the same time as mp3 back in the late 90's, but kinda just sat while mp3 got better) but has really come around in the past 3 years or so.

Now the station is 64kbs aac. I had a few direct mp3 (not reencodes) of addison road sticking with you. I played the first 30 seconds of both the 128kbs mp3 and the new 64kbs aac.

Here is my observations:
mp3 is brighter with harsher symbols
aac is less noisy (vocals really stick out) and symbols are much quieter

[Shane]

The big differences is in the high frequency area as you pointed out. One major problem with MP3 is there are so many versions of it, there is the official Fraunhofer and many hacks of the LAME codec. A lot of people preferred the LAME a few years ago because of the roll off in the high frequencies it introduced to eliminate the obvious coding errors you would hear in lower bit rates. I personally hated the roll off and was never really happy with any of our MP3 streams.

AAC/AAC+ has come a long way, if I had my way and bandwidth wasn't an issue I'd run AAC @ 320kbps or at least 256k, it really is nice... problem is most of our music is encoded at bit rates lower than 256k, so there is a quality issue from the source, and our software still won't play AAC files, it really only wants MP3. The songs that are in high bit rate MP3 sound nice over 320 or 256k AAC, I am listening to it on our LAN now.... sorry to be a tease, but we don't even have the upstream bandwidth at the studio to support 1 stream at that bitrate right now. The 64kbps stream is AAC+, so it's running SBR (Spectral Band Replication) which has an added benefit, the SBR actually adds high back into songs that are missing them from the original MP3 rips we did. It's quite interesting to look at it on an analyzer and see the 64k stream have better high frequency response than a 320k, now on a song that we've recently ripped in the 320k wins hands down. If our software handled it properly I'd actually like to re-rip everything in to WAV or a Lossless codec, but that is a dream at this point.

One surprise is the 24k AAC+ stream, as long as you have a player that will decode AAC+V2 it sounds pretty decent. I was shocked at how good it sounded for 24k. I think with the new limited AT&T data plans when people start listening on their iPhone's and mobile devices more that will be the format of choice.

[nightanole]

And we are back to 128kbs mp3's. Kinda curious if aac 128kbs would sound better since 64 sounded alot better then 64 mp3.