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The difference between latency and overload

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Synchronise sound with visuals - The difference between latency and overload - Timing glitches

If you get timing glitches in Bounce Metronome, it may be due to computer overload but is most likely to be due to latency issues.

Here is how you can tell what is happening.

Contents

Overload

You can get overload on your computer if you have too many programs running - and especially, the likes of anti virus software, scheduuled backups of your computer, defragmentation of your hard disk, and automated scans of your entire computer for viruses or spyware.

When this happens, if the load is really heavy then the rate may drop to just a few frames a second, but each frame will still be pretty much precisely in time with the rhythm because I use the current time to generate the bouncing balls position for the frame.

If your computer is on the verge of not responding, then the animation will kind of get stuck on a single frame for a moment or two then unstick itself, and keep going again and stop and start like that, but each frame still pretty much in sync. with the sound.

The solution is to stop any CPU intensive tasks you have running. With anti virus you may be able to temporarily disable the real time scaanner (best done when not connected to the internet).

How to find the CPU intensive processes

You can get a first idea of where the issue is from the Processes list in Task Manager (Ctrl + Alt + Delete) - click on the CPU heading to sort the processes by the amount of CPU and then do a search for the process name on-line in a search engine if you notice anything with huge amounts of CPU. Some things don't show up there and you can find those under and the Performance tab and go to the Resource Monitor.

Setting the priority high for the animations

In the More (twice) version of More Bugs (Ctrl + 200) there's an option to boost the animation frames to a high priority class. This may be useful on rare occasions if you can find no other way to deal with the CPU intensive processes and tasks.

Latency

This is caused by the synth playing the sounds into an internal queue (techy term: buffer), the sound is waiting in a queue for its turn to get played on the soundcard. The reason it needs a queue is because of the microsoft mixer which lets you have sounds played simultaneously from several programs at once on the same computer. To make that possible the programs have to queue up their sounds before they send it to the mixer, to give the mixer a chance to mix all the sounds together. But normally the queues are really short,

If you get a serious latency issue, like a fifth of a second, then ten times out of ten I find it is an issue with the Microsoft GS Wavetable synth. I don't know of any other synth or sampler with anything like as much latency as it can have. Yet at other times it may be just fine.

It's a well known issue with the Microsoft synth, it can randomly set the length of its internal queue to a fifth of a second (normally) - no-body seems to know why it does it. So all the sounds are waiting in a fifth second queue for their chance to get played, instead of the usual queue which is just a tiny fraction of a second too small to notice. I'd say the chances are very high that that is what the issue is like 99% confident or something, it could of course be some other issue I've never encountered before but this is what it's always been before when users have this sort of issue.

How to confirm that latency is the issue

Try playing from the PC keyboard (Ctrl +K in Bounce Metronome) when it happens. With a large latency it is really obvious, you press a key and the note doesn't sound until a moment or two later.

How to fix it

You can delay the bounce to get it in time with the sounds again in Bounce Options (Ctrl + 220) under "Set Bounce Synchronisation Delay" where you'll need to try different numbers there until you get the sounds exactly in time with the bounce.

The preset delay is 200 ms as that's the latency that the Microsoft GS Wavetable synth often sets itself to on some systems, a massive latency of a fifth of a second. Nobody seems to know why it does it - even in the days of Windows 98 you never needed as much latency as that to play the notes.

Other synth have latency as well, but not as much as this, most users in most situations don't notice it at all. If you play the notes through a sampler or synth that uses the technology called asio to play the notes it bypasses the mixer and has almost no latency at all .

Alternatives

You can adjust the latency of the Microsoft GS Wavetable synth, using Direct Music Producer, though the process is a bit flaky and you will need to run Direct Music Producer every time - details here: FAQ_-_Soft_synths#Microsoft_GS_Wavetable_Synth

Or you can use a virtual midi cable to route the notes from Tune Smithy to a sound font player such as Synth Font, sfz, etc and load a GM sound bank (General Midi sound bank) in the sound font player. Or if it is just for the percussion, you can get sound fonts especially for percussion sounds, load one of those instead, don't need all the other sounds.

You can also install a GM synth such as the Roland Sound Canvas.

Or send the notes via midi out to a hardware sound module, e.g. your hardware synth, and play the notes on its onboard sounds.

Or, if you want to try other sounds, just route the notes to any synth software on your computer. If you want to try them on one of the many VST instruments available, route the notes toa VST host such as e.g. Cantabile lite.

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(By Robert Walker)