FX Buffer Size Changing

[mr_es335]

Hello,

Not too sure if this is an issue or not...



Checked out the SAW HelpFile, but to be honest, it really does not make a whole lot of sense to me.

I do NOT like the idea that this issue is referred to as a "warning message".

I have an important gig coming up in Mid-August and would prefer this error to go away - if at all possible.

As present, I am using SAW as a glorified wave-file player, using the Control Track to send Scene Changes to SAC and MIDI Program Change commands to DMXIS - with DMXIS as a plugin in SAW to send out the lighting commands.

I am not "seeing or hearing" any issues - just want to be sure that what I am seeing is indeed, OK!

Any assistance would be appreciated.

[Dave Labrecque]

Hello,

Not too sure if this is an issue or not...



Checked out the SAW HelpFile, but to be honest, it really does not make a whole lot of sense to me.

I do NOT like the idea that this issue is referred to as a "warning message".

I have an important gig coming up in Mid-August and would prefer this error to go away - if at all possible.

As present, I am using SAW as a glorified wave-file player, using the Control Track to send Scene Changes to SAC and MIDI Program Change commands to DMXIS - with DMXIS as a plugin in SAW to send out the lighting commands.

I am not "seeing or hearing" any issues - just want to be sure that what I am seeing is indeed, OK!

Any assistance would be appreciated.

"FX Buff Chng" simply means that the session has at least one plugin that is altering the buffer size while the engine is active. I believe any latency-inducing plugin does this. This is a warning you don't want to see if you're running SAW in live mode, since it can mean slipped buffers and ever-increasing latency over the life of a live episode. At the very least, it means you're getting latency you probably don't want. However, in the case of your DMXIS plugin, maybe 64 samples is not a problem? I'd be interested to see if you get slipped buffers in that case. If there are additional latency-inducing plugins in the session, of course, your chances of trouble increase.

As for the info in the red box, all it means is that the plugin is showing a latency of 64 samples, and so the SAW engine is at the very least delaying playback that many samples automatically in order to maintain sync. If you'd prefer not to have that slight delay of the audio, you're supposed to be able to enter a value of zero for the "Override Auto Latency Compensation Value," which will disable the compensation (according to the Help file). In that case, while your audio would have no delay on playback, it will be 64 samples out of sync with your lighting commands. I imagine it's fine not to override it. The concern would be whether you're getting slipped buffers. The only way to know is to experiment, I reckon. Try it and see if the the sync doesn't start getting worse and worse over time before you next stop the engine.

What I think is really confusing, though, is that, apparently, if you don't enter a value for the override setting, by default it still displays a value of zero even though it's not implementing that value to redefine the amount of compensation. So, while it looks like the "New Value" is set to override the latency compensation, it's really not. Until you enter a value. And then it looks exactly the same if you enter a zero. Seems like a glaring ergonomic problem to me.

But maybe I don't understand this correctly.

[Cary B. Cornett]

"FX Buff Chng" simply means that the session has at least one plugin that is altering the buffer size while the engine is active. I believe any latency-inducing plugin does this.

The latency introduced by a plugin is determined by the size of buffer that it requires. Larger buffer, higher latency. A plugin can introduce latency without requiring buffer size changes. The size change warning means that the amount of latency may change unpredictably.

[Dave Labrecque]

The latency introduced by a plugin is determined by the size of buffer that it requires. Larger buffer, higher latency. A plugin can introduce latency without requiring buffer size changes. The size change warning means that the amount of latency may change unpredictably.

Thanks for that clarification, Cary. I don't think I've encountered a latency-inducing plugin that doesn't trigger the "FX buffer change" warning. You're saying they exist, if I understand you, is that right?

[Cary B. Cornett]

Years ago I used a free convolution reverb plugin called SIR Verb. It imposed a latency of, I think, 8192 samples. It did not pop of the "buff size chg" warning. AFAIK, that warning ONLY comes up if the plugin changes buffer sizes on its own in operation (during rendering a mix).

[Bob L]

Some plugins absorb buffers before returning real processed data... if they return a buffer of blank samples of the correct buffer size while absorbing the initial samples they need to generate processed output data, then the buffer size flag will not trigger because the program has no way of knowing anything is going on... if they absorb buffers and return buffer sizes of zero or less or more from the original input buffer size, then the warning is triggered.

Bob L

[Philippe M]

Thanks for these explanations, Bob!

[mr_es335]

Bob,

Yes thank you so very much as well!

[mr_es335]

Hello,

My "pee-sized intellect" still has difficulty in "getting my head around" this anomaly!!

So, if I enable "Override Auto Latency Compensation" the "warning goes away.

Is this a "good thing" or a "bad thing"?

I have not touched the "Override Auto Latency Compensation Value" option.

Thus far, I have not had any issues that I am aware of.

[Dave Labrecque]

So, if I enable "Override Auto Latency Compensation" the "warning goes away.

Is this a "good thing" or a "bad thing"?

I have not touched the "Override Auto Latency Compensation Value" option.

Thus far, I have not had any issues that I am aware of.

It appears that by enabling the override, the default override value of zero comes into play. This means there is no latency compensation happening for the relevant plug-in. Assuming you're doing this with the same plug-in we've been talking about, this means that your dmx commands are now delayed by the plug-in's latency amount relative to the rest of the multitrack's audio output (rather than being compensated for, and, therefore, synced with the output). If it's a small enough latency, you likely won't notice it in real life. But, hopefully, it will eat away at your soul that your lighting cues are all late.