Do You Know Your Data Compression?

Do You Know Your Data Compression?

We’re talking about compression – but not the kind you can get from an 1176.

Data compression is a vital part of any engineer’s job – especially if you are delivering final mixes or masters to be used by the client.

For example, if your clients are all putting their music up online, you can offer to give them an optimized file format for doing just that. But what’s the best delivery format for these types of things? What balance should you strike between small file size and high quality audio? Let’s take a look:

The first thing we need to understand is how mp3 data compression “works” when it comes to overall quality. The key factor you’ll need to pay attention to is the bit rate. For mp3’s, this can range from 96 to 320. It is measured in kilobytes per second, and is usually abbreviated “kbps.”

Anything above 192 kbps is going to be basically equivalent to CD quality in the way that the average listener (or even pretty decent listener) hears things. Truthfully, a 320 kbps mp3 and WAV file are almost exactly the same to even the trained listener.

At the same time, anything below 160 is going to start to sound different. There are some artifacts that will show up – only go smaller than 160 if you absolutely must.

So why do we make mp3 files in the first place? To cut down on the file size, of course! A stereo WAV file is about 10 MB per minute. That means a 3 minute pop song is about 30 MB. You can’t do much with 30MB by way of email (10 – 15 MB is the limit for most email services). But a 320 kbps mp3 is only about 2.5 MB per stereo minute. That means you’re looking at not more than 8 MB for a 3 minute track. That is a much more workable size.

mp3 files can get even smaller – 160 kbps mp3 is a little over 1 MB per stereo minute, and a 96 kbps mp3 is just over 700 KB per stereo minute – that’s tiny!

Depending on the final destination, printing your mixes as both a CD quality WAV and a high-quality mp3 is a good idea. A 320 kbps mp3 is going to be very hard – if not impossible – for many to distinguish the difference between. Also creating a 192 kbps mp3 can give you a smaller option to send out, say, in an email.

Once you start to dip below 160, you can start to introduce some more noticeable artifacts. These can be very irritating for your client, and they may blame the mix work. Only create these file types if you absolutely need to.

When delivering these different file formats to your client, be sure to educated them a little bit. Tell them when to use each file format, and give them a clear file structure when you hand over the mixes. Label the different versions as “CD WAV” and “WEB MP3” to help give them a quick reminder when they are distributing their music.