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Topic: ABX Setup (Read 3371 times) previous topic - next topic
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ABX Setup

I'm attempting to understand how to properly test the difference between two files, one a lossless FLAC and one a lossy OGG Vorbis. I have used foobar2000 to convert the FLAC file into an OGG Vorbis file with quality setting q -1 (rated at about ~45 kbps). The music genre is Hip-Hop/Jazz I suppose (Nujabes - Sea of Cloud) if it makes a difference. The FLAC file is approximately 19.2 MB while the OGG Vorbis is approximately 971 KB, so there appears to be a quite obvious difference in stored material. However, when I ABX these files (using the ABX component for foobar2000) I am having an amazingly difficult time determining which file is which as X->A & Y->B or Y->A & X->B.

Should an OGG Vorbis file of this size be this difficult to differentiate from it's lossless FLAC counterpart?

I have a custom built Windows 7 system running on an Asus A8N-E motherboard using onboard audio and running out to a Logitech Z-4 2.1 system. I've also got a pair of Sony MDR-NC6's that I've tested. Am I really just completely tone deaf or is my hardware a big problem? Or... am I possibly doing something completely wrong? Any feedback is greatly appreciated!

[EDIT] Okay, just a quick update. I've found that I probably can distinguish between the two when listening to a track with voice. Also, however, I decided to decode from FLAC to WAV and then from WAV to OGG using the command line this time. I'll do a little more tinkering and testing for the mean time.
 

ABX Setup

Reply #1 –
Quote from: kritter on
Also, however, I decided to decode from FLAC to WAV and then from WAV to OGG using the command line this time.

This will make zero difference, because your conversion software (foobar2000) is basically doing the same thing. It decodes from FLAC to LPCM data (which is the data stored inside the WAV container) and then encodes it to OGG Vorbis.

Quote from: kritter on
I am having an amazingly difficult time determining which file is which [...]
Should an OGG Vorbis file of this size be this difficult to differentiate from it's lossless FLAC counterpart?

Well, it just depends on the sample material, your hearing ability, your familiarity with compression artifacts, conditions of environment and equipment... etc.

Quote from: kritter on
Am I really just completely tone deaf or is my hardware a big problem? Or... am I possibly doing something completely wrong?

You're probably not doing anything "wrong". ~45 kbps is certainly not a rate at which you should expect everything to sound transparent if you have at least an average hearing ability (and in your edit you've already discovered as much). But it seems feasible to me that some material will indeed sound good to an untrained listener (with normal / average hearing) even at such a low rate. You don't necessarily need high-end equipment to competently perform at ABX, and I don't believe there is any direct correlation. In fact, well informed people here have stated that low-end equipment can sometimes actually aid in the ability to detect artifacts.

Well, thats my piece. I'm far from an expert, so hopefully you will be getting much more feedback. Just thought I'd get things started, and hope to have been at least a little helpful.