Latency Best Practices

[random_id]

I have a problem with SetLatency, and I am trying to figure out "Best Practices" for handling it. The problem is related to Cubase and Wavelab. Everything works with the plugins until rendering, then there are problems and crashes. I don't have anything in my code that checks for the rendering status, and I am almost positive it is related to SetLatency.

I have been using something similar for changing latency to this thread (http://forum.cockos.com/showthread.p...hlight=latency). Whenever a parameter changes that affects latency, a bool is set. In ProcessDoubleReplacing(), the bool is checked at the start. If needed, the latency is changed. This has been working well with other host formats. In fact, it was the only way I could find to make Studio One not crash with VST3 format (even though it makes sense to not put the SetLatency() in ProcessDoubleReplacing()).

So, back to my issue with VST3 and Steinberg. A little searching and I found an similar problem with JUCE (http://www.juce.com/forum/topic/repo...lug-ins?page=1). It looks like the solution is to have SetLatency() use an asynchronous callback. With all of the MutexLocks, what would be a good solution?

[random_id]

One other thing to add...

I was focusing all of my efforts on fixing latency with VST3 and Steinberg app; however, a user also informed me of an issue with Bitwig (VST2). In Bitwig, latency is never recalculated. In my limiter plugin, I have oversampling and lookahead, both of which will change latency.

I wasn't necessarily expecting Bitwig to calculate on-the-fly latency like Reaper, but it won't change even after starting and stopping playback. At this point, I have tried SetLatency() in the ProcessDoubleReplacing() (as mentioned above) and in Reset(). I looked at a couple other plugins (I think JUCE-based), and the latency was changing during playback.

[random_id]

I haven't figured out VST3 yet, but I do have something that is helping Bitwig update the displayed latency for VST2 formats
In IPlugVST.cpp

void IPlugVST::SetLatency(int samples)
{
  mAEffect.initialDelay = samples;
  IPlugBase::SetLatency(samples);
  InformHostOfProgramChange();// <-adding this line
}

[Youlean]

Did you figured out VST3 latency report?

[random_id]

Originally Posted by Youlean

Did you figured out VST3 latency report?

I think most hosts do a decent job with VST3 latency; however, I sometimes run into problems with Steinberg stuff. It appears that SetLatency() for VST3 needs to be within a particular thread for it to work.

At this point, I set latency within the plugin's Reset() method. I also have a check within ProcessDoubleReplacing(). I have a bool that is set whenever latency is changed, and will call the SetLatency() if needed.

One other thing I did was add this to IPlugVST3::SetLatency()

void IPlugVST3::SetLatency(int latency)
{
  IPlugBase::SetLatency(latency);

  FUnknownPtr<IComponentHandler>handler(componentHandler);
  if (handler != nullptr){ //added this to prevent crashes
    handler->restartComponent(kLatencyChanged);
  }
}

[Youlean]

Thanks.

Are still using this code for VST2:

void IPlugVST::SetLatency(int samples)
{
  mAEffect.initialDelay = samples;
  IPlugBase::SetLatency(samples);
  InformHostOfProgramChange();// <-adding this line
}

I noticed also crashes in VST3 because of handler...

[random_id]

Yes, I am still using it for VST. I haven't run into issues lately with latency, so I am hopeful that is working on most hosts. I try to test with a bunch, but it is hard to hit every major DAW.

[Youlean]

Great, thanks!