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Playing iTunes' AAC-encoded music on a PC
Authored by: carsten on May 13, '03 07:13:20PM
Music encoded with AAC at the same bit rate as an mp3 file will be slightly smaller than an mp3. That is, provided you encode the AAC and MP3 files from the original uncompressed audio source. (Or, if you bump up the quality/bitrate a bit for the AAC file, you'll end up with the same size AAC file as an MP3 but with higher quality/bitrate.)

Note that converting from mp3->aac, or mp3->aiff->acc, mp3->wav->aac or ogg->aac is an utter waste of time, it's like trying to recompress a jpeg: you will lose quality along the way. You need to encode to AAC directly from the original audio CD.

MPEG4-AAC files are always VBR.

To date I have not heard any compression artifacts in any music I compressed with AAC at 128k, but to be safe I re-ripped my absolute favourite CDs at 160k with AAC. Compression artifacts in mp3 files seem to be very common, but that also depends heavily on which mp3 encoder is used (LAME, or Frauenhofer-based enocder etc. etc.)

My listening tests were done with my Harman / Kardon USB digital audio soundsticks with subwoofer; IMHO these speakers achieve an excellent frequency response, with 4 tweeters in each of the L/R speakers, although the sound tends to be unidirectional (as opposed to omnidirectional).

Note that with the QuickTime Player Pro prior to 6.2, you could select a specific (minimum) VBR for MP4 audio pretty much at any bitrate from 8 to 320kbps by holding down a modifier key and dragging the slider. Unfortunately, now with 6.2 you are strictly limited to the evenly powered bitrates in powers of 2 (112, 128, 160, 192 etc.) iTunes 4 also constrains the bitrate selection in this fashion.

DVDs already use AAC to enode the audio track, so for ripping soundclips or music from movie tracks you can probably skip the conversion to AIFF process (but I haven't actually tried this yet.)

I also updated my iPod to the latest firmware and AAC m4a files sound great there too. By re-ripping my CDs as AAC, I'm now saving about 5-10Mb disk space per album as opposed to mp3s of the same bitrate (128k VBR or 160k VBR depending on the album).

So all my ogg files and mp3 files will remain as-is as part of my collection, until I can get my hands on the original CDs to reencode them as AAC.

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