Do You Hear What I Hear?
By Wayne Maruna
I recently decided to convert my entire CD collection (about 400 discs) to MP3 format for use in an Apple iPod Classic which I can play through my home stereo receiver. The receiver is designed with an iPod port and will display the iPod’s menu screen on our television. I can use a remote to turn the iPod/receiver/TV combination into a huge juke box with instant access to all my music.
You know about MP3 players, right? You probably own one, or have the capability built into your smart phone. All those walkers circling Taberna with wires coming out of their ears are listening to MP3s or some other compressed form of music.
It took me about three weeks to convert all my CDs to MP3s using Apple’s iTunes software, targeting twenty CDs per day. I initially stored the files on my computer’s hard drive, and then synced them to the iPod. While the process became tedious and I was very happy for it to come to an end, it did reacquaint me with music I had not listened to in a long time.
I first wrote about MP3 files and players back in 2005. You can refresh your memory on the subject by reading here: http://pages.suddenlink.net/wamaruna/makemusic.html. A key take-away from that earlier article is the fact that when you convert a CD music file to MP3 format, you significantly reduce the amount of space required to hold the music. This is because the process of converting to MP3 (called encoding) is a ‘lossy’ process, meaning some of the data is thrown out (lost) in favor of reducing file size so as to fit more music into the MP3 player’s limited storage space. What, exactly, gets thrown out? Most often discarded are frequencies that exceed the low or high end of human hearing, or perhaps soft passages right after very loud passages. The encoding software makes those decisions for you.
How much musical data gets thrown out is determined by the ‘bit rate’ you choose to use. This generally ranges from 64 kbps to 320 kbps, with ‘kbps’ standing for kilobits per second. Many encoding programs use 128 kbps as the default bit rate, since the feeling is that this obtains ‘near-CD’ quality. When you convert at 320 kbps, you allow for 5 times the amount of data per second of music as you would at 64 kbps. Of course, the trade-off is that the MP3 file grows in size as well, and you can fit fewer songs in an allotted amount of space. For example, if all your songs averaged three minutes in length, you could fit 364 songs on a 1GB MP3 player if encoded at 128 kbps. If you used a 320 kbps encoding bitrate, you could ‘only’ fit 146 songs on that same 1GB MP3 player.
So What Bit Rate Should Be Used?
As I prepared to start my project, I looked at the possible encoding bitrates I might use. I went web searching to see what people thought to be most appropriate. After all, the higher the encoding bit rate, the better the resulting sound quality, right? Well, in theory, yes. In reality, maybe not so much.
I found the following website very illuminating. The author provides a song snippet that he has encoded at both 128 and 320, and does not reveal which is which. You have to listen and choose. I am notoriously hard of hearing and equally stubborn about not wearing my hearing aids, so it came as no surprise that I made the wrong choice. But it was interesting to note that a higher percentage of people chose the 128 kbps sampling as the clearer sounding file. Check it out for yourself at: http://tinyurl.com/bc7nwt Hey, you've got a 50/50 chance of getting it right.
A little harder test can be found here: http://tinyurl.com/ptgqoo . The author has recorded three songs at every encoding bitrate from 64 kbps to 320 kbps, and has also included the uncompressed file for comparison. It was both surprising and disheartening to realize that my poor ears could perceive little - OK, I admit it, zero - difference between the songs recorded at 64 kbps and those recorded at 320 kbps.
MP3 is just one of several compressed music formats, though probably the most prevalent. Other common types include WMA, M4A, and M4P. And there are certainly other factors that impact the final sound quality, not the least of which is the quality of the initial source. Space does not permit a discussion of all these factors.
Despite everything I just said, in the end I decided that hard drive space is cheap, so I converted my CDs to MP3s using the highest encoding rate. Thanks to that spacious 160GB mini hard drive in the iPod Classic, my 400+ CDs – over 5,500 songs - consumed less than 30% of the available capacity. Picture that – 26 cubic feet of CDs (with jewel cases) reduced to something the size of a cell phone. You better believe I’ve got that baby backed up!