Tuesday, February 15, 2005
Resampling Audio CDs
Maybe it’s just me, but there seems to be some confusion about how ripping an audio CD affects music quality. General perception is that you somehow lose quality automatically when ripping CDs. Here is my understanding of how digital audio works on a computer, and maybe someone can point out if my logic is flawed.
When you burn a standard audio CD on your computer, any music that is compressed, and/or is not 16-bit with a 44.1 KHz sample rate (i.e. an MP3 or AAC file) is digitally re-sampled (by your audio player application, usually during a “Preparing” or “Encoding” stage,) before it is sent to the CD recorder, which then burns the digital information on the disc. This is all done without the use of a Digital-to-Analog Converter (DAC) and thus, you only lose quality if your audio has a higher sample rate than a CD. Given that most people’s music collections came from CD in the first place, we can assume that you’re not going to lose quality at this step.
When you rip a CD to your hard drive, the process works exactly in reverse. The digital information is sent digitally off to the processor to be re-sampled and saved at whatever rate and format you desire.
While there may be no Analog-to-Digital conversion in either of these steps to cause loss, there are still issues of compression and downsampling that happen in the digital domain.
Because 99% of the users probably have their ripping software set to save their music as MP3 files (because near CD-quality MP3 files are approximately 1/10th the size of an uncompressed CD-quality file), this compression process is where the greatest loss of quality will occur.
However, if we set our audio player software to rip CDs using a lossless format (i.e. no compression or lossless compression), and we assume that the sampling is done at 44.1 KHz and 16 bits (the same rate as the CD—anything greater will just waste hard drive space), there should be no loss of quality when you burn a CD from DRM content.
While this process will require a lot more storage, if you’re an audiophile who’s really picky about the quality of their audio, you can back up the entire quality of your CDs. You will then enjoy the benefits of having a music collection that’s prepared for the future with the ability to convert them to compressed files for your portable player as needed.
So, while the general perception is that you somehow automatically lose quality when ripping CDs, with a little thought and planning, you can prevent this from happening.
» Posted by Queue at 11:49 PM (ET)
Category: Cool Technology
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