I am no expert but true CD audio quality is 1411kbps. It is possible to rip it into an uncompressed .wav file. They would be large files, 60mb sounds about right. I dont think idevices can support this either.
EDIT: after digging around I found that higher kbps can be imported and played. The sample rate has to be changed to 48khz though. Apple Lossless, ALAC, AIFF and WAV at over 4000 kbps have been imported. I think these are remastered files because CD audio is only 1411 kbps.
To the human ear (well let's say for most of the general public) 320 kbps is acceptable and sounds great when ripping your cd's and still saves you space which is probably why apple max'd out with this bit rate in iTunes encoder.
I enjoy a high quality lossless setup at home. The sound is really smooth. You know it when you've felt it.
While on the go, although my headphones are pretty awesome, it's probable that with the background noise I really wouldn't appreciate the small details of the lossless, and 320 offers a nice compromise while saving space.
Although we are sadly a minority, most people could listen to 96k on their white pods and not think anything of it.
...after digging around I found that higher kbps can be imported and played. The sample rate has to be changed to 48khz though. Apple Lossless, ALAC, AIFF and WAV at over 4000 kbps have been imported. I think these are remastered files because CD audio is only 1411 kbps.
The files aren't necessarily remastered. Some independent artists will release songs in high-resolution audio files, in the form of FLAC, Apple Lossless, or WAV files.
The audio DAC in iDevices will not handle a 96kHz sampling rate; it needs to be converted to 48kHz. However, the DAC will handle a 24-bit sample size, so 48kHz/24-bit files will play back. A three minute 48kHz/24-bit Apple Lossless file is about 33 megabytes in size, with a bitrate of approximately 1550 kbps.
Note that Macs themselves can support higher bitrates. I have 96kHz/24-bit Apple Loseless files from a few artists, they play great on my Mac, but won't even copy over to my iDevices.
I've settled on 320kbps AAC encoding for classical and jazz music. Regular rock/pop/whatever is ripped at 256kbps AAC.
I don't understand the question. Are you asking specifically about lossy files or anything? 320 kbps is the highest amount for lossy files on an iDevice, but lossless files are obviously higher bit rates. The iPhone definitely supports 1,411 kbps CD quality audio and probably a couple bit rates higher.
I convert .flac to Applelossless files on my computer and have successfully synced/played them on my iPhone. Sound quality is around 800~1411(I believe the highest I have is around 1500) kbps and on average take 20 mb of space for each song. I have found recently that multitasking with my iPhone has become more troublesome, not sure whether from the album art, large amount of music, large file size, or a mixture of the above. But using and playing the files have no lag what so ever. While the large files are unappreciated on the headphones most people buy, having a decent audio system will easily show the difference and on better headphones, spacial quality and clarity is definitely improved.