The few songs I've purchased from iTunes do have an .m4a extension.
Viewing in iTunes:
Bit Rate column = 256 kbps
Kind column = AAC audio file
Viewing in Windows 7 Properties > Detail tab:
Audio Bit Rate = 256kbps
Audio Encoding = AAC (LC)
Viewing in Windows 7 Properties > Audio Properties tab (dBpoweramp-enabled tab):
Bit Rate = 256 kbps
Encoder = AAC (LC)
Audio Quality = Very High (Lossy)
Maybe you have something different that I am unaware even existed in the iTunes Store? If you have have a 16/44.1 file in Apple Lossless (ALAC), then in iTunes the Bit Rate column would likely show somewhere between 500 and 800 kbps and the Kind column would say "Apple Lossless audio file" instead of "AAC audio file".
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Edit: Doing a little research on "Mastered for iTunes" I found:
"Apple touts its Mastered for iTunes tracks on the iTunes Store as “Music as the artist and sound engineer intended.” Mastered for iTunes tracks are therefore supposed to sound better than tracks you rip from CDs. The basic goal of Mastered for iTunes is to provide a direct downsampling of music from 24-bit, 96 kHz files to 256 kbps AAC files, rather than having a first downsampling to the CD format (16-bit, 44.1 kHz), then another conversion to AAC."
So it appears they are 256kbps compressed lossy AAC files with the elimination of an extra downsampling. Better than tracks you rip from CDs? Perhaps, if you are talking about ripping to AAC or MP3, but not as good as lossless rips to AIFF, ALAC, FLAC or WAV.
So I wouldn't expect audio CDs burned from these files to sound much different from the downloaded files, any differences being more attributable to the CD player's internal DAC vs. the file player's player software and DAC, or if using the player as transport only into the same DAC, any differences in the S/PDIF or USB interfaces and cabling.
But I would still expect lossless rips from CDs to sound a bit better.
Steve
