What audio format gives the best sound quality?

FLAC, ALAC, APE, whichever will do.

If you hear a difference, it's just your imagination, or something is wrong with the program you are using for playback, or something went wrong during encoding/transcoding.

None discard audio data.

Lossless is lossless and I agree with Mad Max.

Going out the tangent a little bit, there's a linear relationship between compression rate and decoding complexity, in this regard FLAC is one of the least processor intensive, and the most widely supported lossless format out there, so you'd be trading a few MB for a longer battery life and better support. All things considered I'd go for FLAC.

The chances are your friend has not used anything beyond iTunes for music plaback, AFAIK iTunes still needs something like http://www.simplehelp.net/2008/06/12/how-to-play-flac-files-in-itunes/ <- this to play FLAC, and if your friend isn't very tech savvy he wouldn't have bothered researching this. It is about Apple being Apple, showing their proprietary-loving selves and adopting their "own" format which has no benefit whatsoever. That is not to say FLAC is vastly superior other than offering a slightly higher compression ratio, just that they couldn't bare themselves to join the industry standard, being a cult group they are 

I challenge anyone here, or at Stereophile/wherever, to tell the difference between FLAC and ALAC in a DBT. Anyone at all, even golden-eared audiofools.

 

On a lot of mainstream stuff, I doubt that most of us could tell the difference between 256K AAC and FLAC ....  

 

 

I go with ALAC only because I have an iPod. Before I got it, I was all about the FLAC. Some may argue that WAV is the best, but it doesn't support meta data, and is often twice the file size of ALAC or FLAC. So yeah, in a word; FLAC.

24/96 or better, if you can find it.

For all intensive purposes, ALAC and FLAC are virtually identical, as far as I know. The only digital format I've ever heard of that's hands and feet about it's competition is HD-AAC, which isn't really even supported by anything at all. It is, however, designed specifically to be higher quality than even physical media.

In royalty fees. So... How about I go burn down some HD-AAC encoded files into a DVD right now and create a paradox?
It's no different from Wavpack Hybrid in design, and the lossy stream is an AAC-compliant stream, so there are no major differences in spectral content with alternative formats... aaaand, even if it were (like DSD), it's "no good" that 99.999% of all recording studios use the same 24/96 or 192 PCM format while recording, and even when it's not the case, it still wouldn't matter because at this point the differences are inaudible.

Lossless, in which there are certain types:

 

Uncompressed, i.e. WAV, AIFF

Compressed, i.e. FLAC, ALAC

 

Compressed lossless are only so as a flat file, they are decompressed to 'full size' by the reading software (just as any other archive format).

 

Since I use OS X, ALAC is my choice.

The part in bold is absolute marketing BS, the basis of HD-AAC is still a high resolution PCM which both FLAC and ALAC actually support.

Nicely said. Honestly, the world doesn't need another pseudo lossless format, when there is already a split world between a closed format (ALAC) and an open format (FLAC).

Ah, that's the only bit I remember from a press release when it was first announced. If that's all it is than who cares?

Don't forget Shorten, TTA,, MonkeyAudio, WMA Lossless... and we already have lossy/lossless combined in the form of WavPack and Optimfrog :D:D