Newbie (but important) questions about ABXing
Reply #8 – 2006-02-20 19:02:49
Thanks for the advice, but no one's really answered my main question, which is: If I use my own music, how do I decide what songs to use, and what sections of those songs to use, and how long should each sample/section I cut out be? [a href="index.php?act=findpost&pid=365840"][{POST_SNAPBACK}][/a] Finding the most interesting parts for testing is a matter of experience (and sometimes luck). With a good encoder, there are maybe a few percent of a complete track which may not be transparent. In other words, if you randomly cut short samples from your favorites tracks, it's likely that you're going to miss important issues. On one side testing only problem samples may lead you to wrong and biased conclusions (because these problems should be quite rare and rarity isn't can't make a rule). But on the other side, if you're looking for full and perfect transparency (even with lossy encoders full transparency is possible) testing problem samples would be the first thing to do. Now if your purpose is only curiosity ("but if I really want to know where my transparency threshold is... ") there's no reason to discard samples coming from different musical genres. You should then take a look to the upload forum which contains several problems samples. But if your purpose is more practical (testing before encoding your own library) you should rather focuse on your own tracks and considering foreign samples for training purpose. Finding the right and good samples is a matter of experience you probably don't have at the moment. Don't worry and test what you like (your favorite songs, their best moments): it makes test more enjoying IMO.And how long should each sample be? Not too long. I personaly find 3...5 second samples more practical than 30 seconds ones. Keep in mind that several ABX softwares allow you to choose yout own range during the test. Therefore, using 20...40 seconds long samples shouldn't be a problem. Personally I wouldn't use full tracks. Keep in mind that testing audio codecs is only a matter of comparison. And you can't listen two sounds at the same moment. Therefore, your memory plays an very, very important role. Using very shourt samples could only help your memory and yourself.How many different samples would it be good for me to test before I think I've got a decent picture of what's transparent to me? Testing 100 times the same kind of sound would be a waste of time. 12...20 samples, various enough, should give a good idea of the performance of the tested encoders. The choice of samples is more important than the number. I would in your case spend a complete afternoon to think and finally build a nice sample gallery. I personally built my own gallery of 150 samples for classical music, and it tooks me a good week, if not more. But now I'm glad to have it, and it's a useful (and exhausting ) tool.Should I use headphones or speakers to test Both if you can. Headphones are much better for testing purpose IMO. They reveal more details.Why would I want to use ABX over ABC/HR, or vice versa? ABX tool is only here to confirm the validity of your choice. If you don't have that much experience in testing, I would recommend you to not discard this step. Therefore: ABCHR rating + ABX confirmation should be performed.Chaintech AV-710 with VIA drivers 5.12 (I think), on hi-sample-rate mode Speakers: Logitech Z-2200 2.1 Headphones: Sennheiser HD-497 The high sampling rate mode of your soundcard won't help you at all. Your hardware is clearly good enough to perform listening tests in good conditions. There's no need to bring Klipsch speakers and I'd rather privilege the Seenheiser headphones.