Hotcue response-time issue

General Mixxx discussion.... discuss

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Hotcue response-time issue

Postby pfelts » Fri Jul 13, 2018 7:39 pm

This may be a hardware specific issue, not reproducible on other hardware. But, it surprised me, as I was practicing. I'm glad to discover the issue while practicing and not in the middle of a set. I will try and 'splain what I have experienced.

I have recently started using hotcue to "stutter" the start of a track, as an effect.

1) I hit hotcue 1, on a stopped track, to cue the track at hotcue 1. I use the Mixxx software interface (mouse-click or keyboard) to hit hotcue 1. My simple ION Discover DJ controller has no hotcue buttons. Lol.
2) I hit PLAY (on controller) to start the track at hotcue 1.
3) I hit hotcue 1 again (on Mixxx software interface) 2 or 3 times, very quickly, about a quarter-beat apart, to "stutter" the track.
4) I let the track continue to play. Cool DJ effect accomplished.

This effect works fine, if I'm not also playing a track on deck 2. If I *AM* playing a track on deck 2, while I try to accomplish this effect, I find that no matter how fast I hit the keyboard key or mouse-click on hotcue 1, Mixxx will not respond fast enough to keep up with my clicking. The fastest Mixxx will respond is about a half-beat. I can not achieve a quarter-beat response time. I don't have quantize enabled, btw.

Has anyone experienced this kind of timing lag? I'm using a laptop with an external soundcard (ESI Maya44 USB+), running ASIO drivers. The soundcard came with it's own configuration panel, which allows me to set the soundcard latency. I have tuned the soundcard latency to 144 buffers (4.3ms). From my testing, this is the lowest latency that I can get away with before Windows audio starts to break up. In Mixxx, I have my hardware soundcard latency set to 5.8ms, since Mixxx doesn't offer an exact match of 4.3ms.

EDIT: Ah, this is weird. Mixxx *WAS* reporting a "System Reported Latency" of 4.3ms (0 buffer overflow), which matched the hardware latency I have set using my soundcard's utility. I assumed that Mixxx gets the "System Report" of latency directly from the soundcard driver. That made sense. Now, Mixxx is reporting a "System Reported Latency" of 3.2ms, with a buffer underflow count of 2. Maybe I'm pushing the latency way too low and causing issues. I will try turning it up and see what happens. And maybe I should get a "real" DJ controller, with hotcue buttons.
pfelts
 
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Re: Hotcue response-time issue

Postby kazakore » Sat Jul 14, 2018 9:33 am

What version of Mixxx are you using? 2.1.1 has a bug when Quantise is forced on at all times for HotCue buttons. This means that no matter how quickly you try and trigger it you will only get retriggered on the beats. (You do mention half beats so guess this may not be your issue though....)
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Re: Hotcue response-time issue

Postby pfelts » Mon Jul 16, 2018 11:05 pm

Thanks for the info, kazakore. I'm running Mixxx 2.2.0-alpha-pre. I don't have quantize on for either deck, but it feels like a quantization bug.
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Re: Hotcue response-time issue

Postby kazakore » Tue Jul 17, 2018 11:23 am

[Well the .deb package fails to install on Ubuntu 18.04 so I can't check if it seems the same as the known fault here or not :(


Ahhh Das reminded me I can use the Beta PPA and that obviously will work.

Just tested and can confirm it is the same hotcue quantise but as appeared in 2.1.1

This is the fix with a request to merge into 2.1 branch for 2.1.2 release but not yet done. I'm sure how or when 2.1 commits make it into the 2.2 Master branch though....
https://github.com/mixxxdj/mixxx/pull/1715

(Personally I'm building myself and merging 1745, 1715 and 1716 together as they each fix bugs I find rather irritating....)
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Re: Hotcue response-time issue

Postby pfelts » Fri Jul 20, 2018 11:51 pm

Thanks, kazakore. I subscribed to bug #1777429, so I can get updates on this quantization bug.
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