Monday, September 27, 2010

ABX testing - how sensitive are your ears to music quality?

Being a self proclaimed audiophile, I have always ripped my music to lossless or high bit rate formats without really bothering to ask whether my ears were sensitive to the quality difference between different codecs. I did not have to worry as long as I had a 20 GB HDD on my MP3 player. But when I bought my 8 GB Cowon D2 and started buying SD cards to load additional music, I was forced to do a trade off. I could load lesser, and high quality songs on my player, or I could have more songs at a lower bitrate. Would my ears notice the difference or not? I decided  to do an ABX Test.

To put it simply, an ABX test is a blind test using the same song, encoded at two different bitrates.

This post on The Mistic River forums is the simplest description and procedure for ABX testing that I have ever found.

I will summarise the steps here:

1) Get the Foobar player
To do ABX testing you need to download the Foobar 2000 player. Also you need to install the ABX testing software which is a third party module.  You can find it here on the Foobar site. You will have to download the file (it's a .dll file extension) and then install it manually into the Components folder of Foobar.

2) Choose the song
Choose a song which you want to test (the Mistic River post gives some useful tips). Rip it from CD to different bitrates (for starters you can rip it to 128, 192 and 256). Load any two rips into the Foobar player, right click on both and select Utilities/ ABX two tracks as shown below

The player will prepare the test and present you with this window;

The interface is self explanatory. The software shuffles the two options and presents each one to you twice - as A, B, X and Y. You have to listen to all 4 and then guess if A is X or Y, and if B is X or Y. You repeat the test multiple times to eliminate randomness and luck. If you correctly match the song clips, say more than 10 times out of 15, you are really hearing the difference. Note that in this test, you are never asked to guess which is the higher bitrate, you are merely matching the song clips after listening to them.

The set-up of the test is a little time consuming but once you have it all installed, it's a fun test for you and your friends and family to take. Want to know my results? I can tell the difference between 128, 192 and 256! So I guess it makes sense for me to encode at higher bitrates!