Can iTunes now play HD music files in high definition? A record company is offering free downloads of high-definition music. I downloaded several music files encoded at 24 bit, 192 kHz ALAC. To my surprise, iTunes 12.0.1.26 on  10.10.1 Yosemite imported the track and played it successfully! And it lists that high-resolution information in the file information.

I had thought that iTunes could not play high definition files. I understood it to be limited to 16 bit, 44.1 kHz files. And so I had thought that special software is required to play anything higher than that.

So my question is: When iTunes is playing such files, is it actually playing them at full resolution, or is it down-converting them? (Or whatever the technical term would be for storing or playing the files at something less than full resolution.) I can't tell by ear because I don't have my computer hooked up to good speakers.
iTunes uses the same technologies as QuickTime for playback. 

According to this document circa 2005, QuickTime is capable of playing 24-bit , 192kHz audio files. I think it's safe to say that iTunes is fully capable of playing these files.

However, you're probably limited by the hardware in your Mac. If you open the "Audio MIDI Setup" app, you'll probably find that your Mac is limited to audio output at 96kHz.



So, if you want to listen to these files in full 192kHz, you'll need to use a dedicated external USB DAC, and bypass your Mac's internal audio hardware. Please correct me if I'm wrong.

Further reading: http://www.head-fi.org/t/671361/how-to-get-24-bit-192khz-files-from-my-macbook-pro-to-play-through-the-dac-of-the-fiio-e17