### FAQ: Automatic Plugin Delay Compensation (PDC) In Renoise ###
As noted in the release announcement, Renoise now fully and automatically compensates latencies which are caused by either plugin FX, instruments or Renoises internal FX. There is no configuration needed, except that you can turn PDC On/Off globally (next to the VU meter, or in the audio preferences tab). Whatever routing you use in Renoise (sends, routing to external sound-card channels), it will “just work” automatically. Latencies from rendering and sample FX processing will also be fixed. Meters (Track scopes and the mixers meters) are compensated/synced as well.
Why are there latencies with some FX? Depending on the type of FX, sometimes latencies can’t be avoided. For example many compressors have a very small latency for look ahead signals. Other FX like FFT filters and some reverbs process the sound with latency because of their algorithms. Finally some hardware FX cards which offer VST interfaces also add latencies, as the signals have to be routed to the hardware and back which takes a bit of time.
Why do you need PDC? Even if you are not using plugins, the small latencies from Renoise’s built-in FX (Compressors, Gate) are important to compensate and control when it comes to subtile things like the “groove” of a song.
How does it work? Latencies can only be compensated by “shifting” the other signal paths that are not affected by the FX latency (other tracks). Shifted by such an amount that the final latency of all signal paths “match”. So if you are using lots of plugins with high latencies you might notice a small “lag” in the whole song - an extra delay in everything you do in Renoise (for example Recording). To make recording easier you can temporarily disable PDC, record your stuff, then enable it again.
What does not work? Renoise can only fix latencies if the plugin correctly reports it. So if you notice a delay where none should be, try to find out which plugin causes the delay. Please note that bypassing an FX will NOT bypass the delay. You have to remove/delete the plugin to test this. Renoise will delay inactive (bypassed) FX to keep the overall compensation in sync when, for example, DSP bypassing is automated.
If you find a plugin which does not report the correct latency, please report the problem to the author of the plugin. We can not and will not add workarounds for buggy plugins. The authors of the plugs have to fix this.
Analyzing what PDC does: You can see how much delay an FX Instrument causes by hovering over the “?” button on the plugin in Renoise. Also in Renoise’s “View” menu you’ll find the option “Show PDC info”. This will give you a list of which FX/Instrument cause which delay and which delays Renoise compensates. This option will be removed in the final release.
There’s also a hidden internal FX to test PDC in Renoise. Copy the XML data below into the clipboard (Control/Command + C), then activate Renoise and right click somewhere in the free space of the Track FX chain. There, choose “Paste device”. This will add an internal test FX which does nothing more than add adjustable latency, so you can see how Renoise compensates the audio tracks for yourself…
<?xml version="1.0" encoding="UTF-8"?> <filterdeviceclipboard doc_version="0"><br> <deviceslot type="PdcTestDelayDevice"><br> <isactive>true</isactive><br> </deviceslot><br> </filterdeviceclipboard>