AAC encoding issues: Muffled sound

MacFixIt reader Jorge Padilla reports a problem with AAC audio quality that we have not experienced in house, and for which we are seeking confirmation:

"This is a bug I?m experiencing specifically with one song; sadly, it?s a classic song: Jump by Van Halen. I have this song on 2 albums I bought: Van Halen Best of Volume I and the new compilation Van Halen Best of Both Worlds.

"Basically what happens is that when I encode that specific song with AAC (I tried only 128 and 160 bits) the beginning of the song sounds muffled (when the opening synth starts, arguably, one of the key moments of the song) but after fractions of a second it carries on perfectly. The odd part is I already had the song encoded in old version of the software (iTunes 4.0 and QuickTime 6.0.2) and sounded perfectly, and I wanted to reencode it because its one of my favorite songs and because the new QuickTime 6.5.1 sound so much better to me. This problem affects the same song in both albums. And also, this does NOT happen if I use Apple Lossless Encoding, AIFF or WAV (haven´t tried mp3 nor want to really).

"I tried this in my iBook G3 800MHZ 12? OS X 10.3.4 iTunes 4.6, Quicktime 6.5.1 640 MB ram. And my family?s eMac 700 MHZ, same os and software and in both computers happens."

If you are experiencing problems with muffled sound on any AAC encoded tracks, please drop us a line at late-breakers@macfixit.com.

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