Today’s question tests the old adage that says there are no dumb questions, only dumb answers.
“If I make a 24 bit CD, will it work on all consumer CD players?”
I realize most of our readers already know the answer to this, and therefore this “tip” may not be all that helpful, but in our modern day world, which is increasingly becoming a 24/96 (or more) world it may be prudent to remind everyone that our primary delivery format, the compact disc, is a 16-bit, 44.1 kHz format. This rule is one of the principle components defined in the Red Book standard, and as such no currently available CD player can deal with any other sample rate or bit depth. Some models may tout 18 to 20 bit D/A converters, but this has nothing to do with the audio on the disc, only the machine’s ability to play it back more linearly.
If you are working with audio of higher bit depths or sample rates (as many of us now are) you need to find a way to convert it to a form suitable for compact disc. The issue is pretty cut and dried on the sample rate front: you just can’t pour 88.2k or 96k samples per second into a format set up for 44.1. You will not get very far if you try. You must first convert the sample rate of your audio to 44.1 kHz. Sample rate conversion algorithms are much better now than they were five or ten years ago, but some of them still leave much to be desired, which is one reason why many engineers aren’t too gripped with trying to record at higher sample rates. Of course the DVD is starting to change these paradigms, but right now “most” people still record at 44.1 and avoid the sample rate conversion issue altogether.
The bit depth aspect of the equation is much more insidious because quite often you can send 24-bit audio to a digital input that only accepts 16-bit audio and it will simply ignore the extra bits. You may think you are getting a 24-bit transfer, but you’re not. I can promise you that if you are pushing 20 or 24-bit audio into a CD recorder’s digital input you are not putting any more than 16 bits on the CD. (There are some optical recorders, such as the Alesis MasterLink, that can make 24-bit discs, but these only play back on those machines. They are not Red Book compliant.) Rather than let the destination device simply “truncate” those extra bits off of your signal you are better off to use some sort of dithering process to lower the bit depth. If you burn CD’s on your computer you will have to convert your files to a 16-bit format in order for the CD to play on any CD player. Again, the best way to do this is through a dithering process. There are many types of dithering available in a number of different hardware and software forms. The quality and effectiveness of the different types is a subject that is as hotly debated as sample rate conversion utilities, but unlike the sample rate conversion issue most engineers agree that dithering 20 or 24-bit audio down to 16-bit often results in higher quality than simply working with 16-bit audio all along.