I've tried several ABX applications on my MacBook: the Java version (0.52b) for Mac, Foobar and WinABX while running bootcamp/XP.They all produce audible artifacts when switching between A & B. For this test I used 2 identical sinewave files.I'm curious if this problem may be linked to my setup or if it's a known issue that doesn't seem to bother anyone ?Thanks for your help.
For example, I can reliably ABX the QSC ABX box with nothing attached to it even if it is on the other side of the room.
When I have some time I'll try to capture the signal with artifacts to illustrate. It's something like a crack, click or pop. It doesn't sound like zipper noise IME.Since digital cross fading has been around for over 30 years, I'm rather surprised that the ABX applications can't switch without artifacts. Music editing is part of my job so perhaps I'm more sensitive to the artifacts than the average listener.Can we agree however that artifact free switching between identical signals should be easy to implement (in the digital domain)?
Quote from: Arnold B. Krueger on 31 March, 2010, 09:11:05 AMFor example, I can reliably ABX the QSC ABX box with nothing attached to it even if it is on the other side of the room.Was that caused by switching artifacts, or were the A and B paths too different ? Did that change when the inputs were properly terminated ?
Yes, ABX programs click on switch because they stop playing one file and start playing another, and I agree that it is disturbing. I also agree this could be improved
This is an interesting subject.To get 100% artifact free track switching, the application would need to employ some kind of low-latency playback scheme and switch streams being sent (with a short crossfade) by itself without interrupting the output.
That's not needed at all. All you need is a small small deque buffer. A switch causes the last few samples filled (from the left) by stream 1 to be invalidated, replaced with a crossfade between stream 1 & 2, and then stream 2 takes over. Output is pulled continuously from the right side of the buffer.
@Kees de Visser: Can you reproduce the artifact with real-life audio, not sine waves?
The only reliable solution to this problem is probably to insert a short mute (with fade-out/fade-in) during the switch, although that could have an influence as well (any ABX expert that wants to chime in ?).
Here are a wav sample and its waveform of the java ABX application's output (on a MacBook).I couldn't find an easy way to capture the output of foobar while running XP/Bootcamp. If it can be helpful I'll try again.For this test I used a 600Hz sine and a 600Hz+5Hz sine mix, just because they sound identical and look very different.WAV with ABX artifactsThe artifacts are identical for L and R channel and are pretty random, which is probably a good thing, although artifact-free switching would be better.
What is with the artifacts in the middle of the segments with signals?
Quote from: Arnold B. Krueger on 05 April, 2010, 08:15:26 AMWhat is with the artifacts in the middle of the segments with signals?Those are switches between identical signals, like from A to A, or A to X and X to A when X=A.
For maximum sensitivity, there should be no clicks or pops in the ABX playback. The two signals should be Hann windowed (or some other simple window) together for a total gain=1, moving between the two signals.
Nitpick question: should the window generally be power complementary, amplitude complementary.. or both?
The two signals should be Hann windowed (or some other simple window) together for a total gain=1, moving between the two signals.
Think of the extreme case when comparing a signal with its polarity-inverted version (e.g. to test audibility of absolute phase).
Quote from: Woodinville on 05 April, 2010, 03:26:49 PMFor maximum sensitivity, there should be no clicks or pops in the ABX playback. The two signals should be Hann windowed (or some other simple window) together for a total gain=1, moving between the two signals.Nitpick question: should the window generally be power complementary, amplitude complementary.. or both?(EDIT: Obviously the assumption here is power complementary)
So why is correlation an issue?