All of the major online MP3 music stores compress their music, most opt for MP3, whilst iTunes goes for the more advanced AAC codec. Regardless of the technology, information is being lost as a result of the encoding process, and the buyer must ask themselves key questions such as; what quality is good enough for me or, can I tell the difference between different bit rates and file formats?
Some people may scoff at iTunes deciding to encode their audio at 128Kbps (iTunes plus songs are 256Kbps), saying there is just not enough information retained to make the song worth listening to. Play.com encodes its MP3s at 320Kbps, a substantially higher bit rate, but is it possible to tell the difference? As AAC is a more advanced codec than MP3, a song encoded using AAC should sound better than one encoded using MP3 at the same bit rate. But how much higher do you have to encode an MP3 at before it sounds better than AAC?
Source songs and audio test
I downloaded the Alexandra Burke version of Hallelujah from iTunes in AAC format (128Kbps, 3.5MB in total) and also from Play.com in MP3 format (320Kbps, 8.3MB).
I listened to the two versions being played back to back on a variety of audio equipment; standard iPod earbuds, Etymotic ER6i earbuds, Sennheiser headphones, Bose Sounddock and hi-fi separates (Denon amp and Mission bookshelf speakers).
After careful listening I came to the conclusion that I couldn’t tell the difference, on any of the audio equipment. I honestly thought I would hear some difference, more detail and frequency range in the Play.com MP3, but no, I couldn’t find anything different. As well as appreciating music, I’m also a musician, but was it just me who couldn’t tell the difference?
I recruited another pair of ears to listen to both versions of the song being played back to back, and when asked to choose which version was the higher quality recording, they chose the iTunes AAC version.
So is the bit rate marketing all nonsense or is Play.com not using a good enough encoding process?