Using iTunes To Convert MP3's
Sound Quality/File Size
Becoming a well-rounded multimedia designer can get expensive: sometimes it seems you have to master new software packages every day. I am often asked if there is a quick, easy, and free way to convert sound files into MP3s. Guess what - the answer is staring you right in the face: iTunes!
Today we are going to use iTunes to convert an MPEG-4 file into four MP3s of differing file size and sound quality. We will preview the results and decide on the right combination for your projects. First, let's briefly examine the two main variables you will be experimenting with: Bit Rate and Sample Rate.
Bit Rate is measured in bps (bit per second) and refers to the number of bits processed per second. With audio files, bps is in the thousands, and thus prefixed with k. 4kbps is four thousand bit per second. Most designers would express this simply: Four kilobit.
You bit rate selection should span between 96kbps (which is FM stereo quality) and 192kbps. "CD quality" bit rate is over 300kbits, but makes for AWFULLY big file size.
Sample Rate (sometimes called Sampling Frequency) is measured in Hz (Hertz) and refers to the number of samples per second taken from a continuous signal. MP3s have sample rates measured in the thousands of Hz, which is expressed as kHz (kilohertz).
Although changing the sample rate in iTunes does not have a huge effect on final file size, it is important for Flash projects! Flash prefers to work with sources sampled at a rate divisible by 11. Always choose a sample rate of 11kHz, 22kHz, or 44kHz
You can click the Launch MP3 Player link below to hear the same song sampled four different ways: