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Latency- a definition, and Traktor DJ Studio
Tue, 01/13/2004 - 15:43
[ I wrote the original version of this in a discussion about latency in the Traktor DJ Studio forums,
Keeping in mind that:
1000 Milliseconds = one second
100 ms = 1/10th of a sec = .1 seconds
50 ms = 1/20th of a sec = .05 seconds
10 ms = 1/100th of a sec = .01 seconds
Latency is a common term in recording studios, and is used to describe the total time for a signal to go IN AND out of a digital recorder. Every conversion to/from digital inherently takes some amount of time, depending on the particular converter chip used. That value sometimes increases when a digital audio workstation has more processor-intensive things running (plug-ins etc) The resultant delay can throw off a musician's timing when they are trying to play along with previously recorded tracks.
With Traktor DJ Studio, the only thing we have going IN is our commands, be they on-screen buttons, keyboard commands or another external controller.
OS X's process viewer application tells me that as the latency is increased, processor load decreases. But I note that at the highest settings (selecting the Mac's "built-in" output, I can crank Traktor 2.5.1's latency up to 255), reaction time to the EQ band kill button (and others) seems slower. But 200ms is still only 1/5 of a second.
The cue/pause button is definitely affected by latency too. Try this:
Load a song in deck A and cue it up to a snare hit.
Load a fast (150+) bpm song in deck B and play it.
Rapidly hit Deck A's cue/pause button to play along with Deck B's rhythm, using it like a drum pad.
Do this at both high and low latency settings.
At high latency settings (200ms+), it doesn't work at all for me. Dial it down to 10ms and it works great.
OK, so we have a relationship: higher latency means slower control responsiveness. But lower latency puts a higher load on the processor. So we need to find a sweet spot to avoid slow button response or sluggish playback.
So, a sweetspot can be determined depending on your needs. I had been trying to get my latency as low as possible (as is the goal in recording studios) but now I think I'll lighten the load on the processor a bit. For my needs and processor power, something in the range of 25-30ms seems fine. If I need to make super-precise timing-sensitive moves like that described above, I can always decrease the latency.
(A related factor is the smoothness of each deck's waveform display. But this seems to be smoothest at middle settings? Why would it slow down at high latency settings?)
If you are a Traktor user, you'll find my complete guide to FireWire & USB audio interfaces useful...
To buy Traktor DJ Studio, try these links: