Does system performance matter when rendering not in real-time?

DSP, Plug-in and Host development discussion.
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228 posts since 3 Feb, 2014

Post Fri Apr 11, 2014 3:30 am

Please excuse my clueless-ness. I did implement a VST once, but since have forgotten the details of the spec.

From a professional VST I bought, I am getting crackling noise when I render my project to wav file (but no problems when I play the project in real-time inside my DAW). It has been suggested that my system might be too slow, but I don't see how system performance would matter during the process of rendering a project to wav file. When rendering to a wav file, don't VST's have the luxury of having as much time as they want to process the audio? Doesn't the DAW waits patiently until each VST has processed each block of audio? Am I remembering the VST spec wrong? Why would system performance matter during rendering?
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KVRian
554 posts since 1 Jan, 2013 from Denmark

Post Fri Apr 11, 2014 7:07 am

If the plugin is coded properly, no, performance has no interference. It might handle non-realtime (offline rendering in vst-terms) differently, though.

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KVRAF
4051 posts since 6 Nov, 2009

Post Fri Apr 11, 2014 7:12 am

*what vst?
*what daw?
*what asio driver/interface?

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Topic Starter

228 posts since 3 Feb, 2014

Post Fri Apr 11, 2014 7:25 am

* EWQL Spaces
* Reaper
* Line 6 Pod HD ASIO driver/interface

The addition of the Pod HD and the switch to its driver came a day before I experienced the crackling noise. But, when I turn off Spaces and re-render, there is no crackling noise, so that is more precisely what I mean when I say the noise is 'from' the VST.

I was assuming the Line 6 driver would play no role in the render-to-wav process, since offline rendering involves no input or output to the Pod. Was I wrong to assume that? Why do you ask about the interface and driver?
Last edited by BachRules on Fri Apr 11, 2014 7:35 am, edited 2 times in total.
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Topic Starter

228 posts since 3 Feb, 2014

Post Fri Apr 11, 2014 7:32 am

Mayae wrote:If the plugin is coded properly, no, performance has no interference. It might handle non-realtime (offline rendering in vst-terms) differently, though.
If I remember the VST spec right, the DAW informs the VST whether it's working in realtime or offline. The VST has the option of taking advantage of offline mode and doing things differently, which could cause problems specific to rendering if there's a bug in the specialized offline code. Or, even worse, a wrongly coded VST might pay attention to realtime even when it's rendering offline, which could cause problems if the rendering went slower than realtime.

Thanks for the reply. I wasn't positive whether I was remembering the VST spec right.
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Topic Starter

228 posts since 3 Feb, 2014

Post Tue Apr 15, 2014 8:09 am

For discussing their bug, EastWest has banned me from their forum, and writes:
you obviously have system problems, you need technical help to resolve them;
I tried to reply,
What kind "system problem" could possibly cause crackling during rendering? I have a degree from CCRMA. You obviously are mistaken and blaming your product's defect on a customer.
but EastWest censored it. They also wrote:
our software (all of it) has passed the AU and VST specification....
to which I tried to reply:
What is that even supposed to mean? During rendering, does audio-quality depend on system speed or doesn't it?
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KVRian
554 posts since 1 Jan, 2013 from Denmark

Post Tue Apr 15, 2014 8:27 am

Can you reproduce the problem in another situation (ie. another daw, maybe another kind of plugin (vst/au/rtas etc.))?

Thanks for the heads up though. Censoring and banning is the telltale sign of a bad company; wont be buying anything from them.

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Topic Starter

228 posts since 3 Feb, 2014

Post Tue Apr 15, 2014 8:34 am

Mayae wrote:Censoring and banning is the telltale sign of a bad company;
I think so. They have their users believing the audio errors during rendering are the users' fault, and they want to maintain that lie instead of fixing their VST.
Mayae wrote:Can you reproduce the problem in another situation (ie. another daw, maybe another kind of plugin (vst/au/rtas etc.))?
I don't have another VST host besides Reaper. I did a new test, adding and subtracting VST instruments to my Reaper project, but not sending MIDI to them. The more VST's I added, the more audio problems there are when Spaces renders. So somehow its rendering code is dependent on system speed.
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KVRian
554 posts since 1 Jan, 2013 from Denmark

Post Tue Apr 15, 2014 8:49 am

BachRules wrote:
Mayae wrote:Censoring and banning is the telltale sign of a bad company;
I think so. They have their users believing the audio errors during rendering are the users' fault, and they want to maintain that lie instead of fixing their VST.
Mayae wrote:Can you reproduce the problem in another situation (ie. another daw, maybe another kind of plugin (vst/au/rtas etc.))?
I don't have another VST host besides Reaper. I did a new test, adding and subtracting VST instruments to my Reaper project, but not sending MIDI to them. The more VST's I added, the more audio problems there are when Spaces renders. So somehow its rendering code is dependent on system speed.
It could sound like the plugin is rendering multi-threaded, and the threads can't keep up somehow, causing buffer underruns - possibly caused by the host offline rendering in threads as well, causing less time per thread..
It's still no excuse though, threads should be synced obviously.

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Topic Starter

228 posts since 3 Feb, 2014

Post Tue Apr 15, 2014 9:06 am

Mayae wrote:It could sound like the plugin is rendering multi-threaded, and the threads can't keep up somehow, causing buffer underruns - possibly caused by the host offline rendering in threads as well, causing less time per thread..
It's still no excuse though, threads should be synced obviously.
Maybe you are suggesting a bug in Reaper (the host)? That would be technically possible, but I think unlikely, because the guys making Reaper seem very competent.
Last edited by BachRules on Tue Apr 15, 2014 11:16 am, edited 1 time in total.
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KVRAF
6306 posts since 30 Dec, 2004 from London uk

Post Tue Apr 15, 2014 9:21 am

Most people don't realise that low latency audio requires some settings to be changed on your PC. It is a specialist area. One that CCRMA obviously didn't cover :

https://www.steinberg.net/en/support/kn ... -daws.html

A tool to help diagnose DPC issues :

http://www.thesycon.de/deu/latency_check.shtml

Its well known that some laptops cannot do low latency well due to chip set issues.

Quoting a degree to a company trying to help isn't going to do you any favours.
Last edited by UltraJv on Tue Apr 15, 2014 9:28 am, edited 1 time in total.

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Topic Starter

228 posts since 3 Feb, 2014

Post Tue Apr 15, 2014 9:26 am

UltraJv wrote:Most people don't realise that low latency audio requires some settings to be changed on your PC....
That link is about working with audio interfaces, but rendering to disk doesn't involve any audio interface does it? Rendering to disk isn't "low latency audio" in the sense you mean. Rendering to disk is just reading from disk, doing a lot of adds and multiplies, and writing back to disk, with no time pressure to perform the computation.

Please clarify: Are you saying that VST's you code can't render correctly on regular or slow systems?
UltraJv wrote:Quoting a degree to a company trying to help isn't going to do you any favours.
It was in response to their saying things that weren't going to do them any favors ("you obviously have system problems.... our software (all of it) has passed the AU and VST specification....")
Last edited by BachRules on Tue Apr 15, 2014 10:29 am, edited 2 times in total.
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KVRAF
6306 posts since 30 Dec, 2004 from London uk

Post Tue Apr 15, 2014 9:29 am

BachRules wrote:
UltraJv wrote:Most people don't realise that low latency audio requires some settings to be changed on your PC....
That link is about working with audio interfaces, but rendering to disk doesn't involve any audio interface does it? Rendering to disk isn't "low latency audio" in the sense you mean. Rendering to disk is just reading from disk, doing a lot adds and multiples, and writing back to disk, with no time pressure to perform the computation.

It took you seconds to dismiss the help that you didn't try. Youll do well on here :D

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Topic Starter

228 posts since 3 Feb, 2014

Post Tue Apr 15, 2014 9:33 am

UltraJv wrote:It took you seconds to dismiss the help that you didn't try. Youll do well on here :D
Are you saying that VST's you code access the audio interface while merely rendering projects to disk?

Please tell me more about how you design your VST's? Does their performance depend on the weather and the date too?
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Topic Starter

228 posts since 3 Feb, 2014

Post Tue Apr 15, 2014 9:36 am

UltraJv wrote:Most people don't realise that low latency audio requires some settings to be changed on your PC. It is a specialist area. One that CCRMA obviously didn't cover....
Actually they covered it. We rendered in LISP sometimes, really slow, taking breaks for garbage collection, etc. And yet, when the final WAV emerged, it had no crackling. That's the whole thing about rendering. R-e-n-d-e-r-i-n-g, which the links you posted do.not.even.mention.
Last edited by BachRules on Tue Apr 15, 2014 9:51 am, edited 2 times in total.
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