Any recommendations for compression quality settings?

[waxcylinder]

I have overfilled my "old" 30gb iPod and plan to buy a new Classic 160gb - this will give me an opportunity to upgrade the quality level of sound files on the iPod - and I wondered what people's recommendations are for "best practice" in terms of quality settings.

Up till now I have been exporting projects from Audacity as MP3 at 192 for rock/pop/folk/jazz and MP3 256 for classical. I have also carefully kept and backed up WAV files of every track - and mostly made music CDs. (And BTW - my commercially bought CDs I ripped at AAC 192). My original choice of 192 was a trade-off compromise sound quality versus disk occupancy.

On a bigger iPod:
1) should I re-import into iTunes from the CD's I made at 256 AAC (or even 320)
2) or can I go from WAV file on PC to iTunes without using the CD - i.e can iTunes import ann AAC from a WAV input
3) should I re-import using Apple lossless (I wouldn't have space on even a 160gb iPod for all tracks as WAVs)
4) should I re-rip my commercially produced CDs at a higher AAC bitrate or Apple lossless as above.
5) should I not bother and just leave things as they are.

I do listen to the music on high quality Sennheiser headphones on the iPod - and plug the iPod into the AUX input of my hi-fi - so sound quality is a material question.

Any advice or insights will be greatfully received, thanks,

WC

[alatham]

I'm not convinced that the DACs on the iPOD are of high enough quality to benefit from re-encoding. I might be wrong though.

Personally I would make a few tests and see if you can actually tell the difference. The best way to do that is to do a real A/B test.

You can set one up by importing a 192 kbps file and a higher bit rate file into Audacity and cutting the signal up so that it switches between the two (make sure there are no artifacts during the switch, and make sure the relative volumes are identical, ideally you should use the same encoder to make both files). Then export that test signal as a wav (so there's no loss) and listen to that using your new iPOD. If you can hear the transition from one bit rate to another, then your setup is good enough to benefit from higher quality files.

[waxcylinder]

Thanks for that suggestion for a test scenario, Andy. I'll give that a try when I make the purchase.

There are two upsides of not re-importing:
1) saves a lot or work and time
2) keeps more iPod space free - hence more music.

WC

[waxcylinder]

For the benefit of any others who follow this thread, I am posting here a quote from Koz (from a reply to a totally different thread on the 1.2 MAC forum). It sheds some interesting light on this issue .....

With degraded 60-year old ears, 30 year old technology is probably good enough for me - but those starting a similar vinyl conversion project may like to consider recording at Koz's suggested settings.

WC

You know that 44100 was the compromise scan rate that they used 30 years ago so they could push audio CDs out the door without violating too many physical rules. Using a graceful Nyquist transform, you can't get an audio CD frequency response much beyond 17 KHz. FM broadcast is 15KHz. 48000 will take you out to 18.5KHz. with a few tricks to make it to 20 KHz., the generally acknowledged upper end of human hearing.

Audio CDs are the only ones still using 44.1. DAT, DVD-PCM, Broadcast, DV, all dropped 44.1 like a hot rock in favor of 48. 16 bit stereo audio is generally considered to have a dynamic range of high 80s or better, I think 96 is the theoretical limit. What are you doing that needs better than 20 dB headroom and 65 dB noise floor? That's enough to have silent speakers in a quiet room and still be able to knock over a vase with a drum beat. Most analog audio amplifiers won't go beyond that. I did a live vocal performance at 48K/16 and my microphone amplifier and room noise killed me long before I hit the digital limits.

iTunes will accept 48 KHz/16 just fine and convert to excellent quality 256-AAC (custom rates available out to 320) for your iPod and back out to 44.1 for recording audio CDs. The audio CD will be the lowest quality thing in that whole chain.

Koz