KVR Audio

Aleksey Vaneev · Post by **Aleksey Vaneev** » Mon Feb 13, 2006 4:01 am

Hello there!

I'm currently trying to collect information about different VST hosts and their MIDI data handling relative to plug-in latency.

For example, if I send MIDI CC to change some internal plug-in's parameter, will host delay MIDI CC's time of arrival to match plug-in's latency value or not? Or should plug-in do delay on that MIDI event on its own so that event's timing is right?

I'm not asking this question on specialized developer forums because I would like to hear actual user experiences with different hosts. Since VST specification does not explicitly state how MIDI data is handled in this situation, different hosts may behave differently. Hence the question.

Best regards,
Aleksey Vaneev of Voxengo.

Aleksey Vaneev · Post by **Aleksey Vaneev** » Mon Feb 13, 2006 4:18 pm

OK, seems like I have to investiage this myself... That was a too 'techie' question I guess.

Rock Hardbuns · Post by **Rock Hardbuns** » Mon Feb 13, 2006 4:44 pm

For example, if I send MIDI CC to change some internal plug-in's parameter, will host delay MIDI CC's time of arrival to match plug-in's latency value or not?

Well, the midi messages are timestamped in relation to the start of the current sample buffer, so if the buffer moved in relation to the "master time" logic suggests that the midi messages should be offset accordingly.

Aleksey Vaneev · Post by **Aleksey Vaneev** » Mon Feb 13, 2006 4:51 pm

Rock, yes, I do think the same. I'm just worrying that some hosts may do this for plug-in automatically. I just want to be sure no hosts do this.

Rangtangtang · Post by **Rangtangtang** » Mon Feb 13, 2006 5:01 pm

Anyway to test?

Aleksey Vaneev · Post by **Aleksey Vaneev** » Mon Feb 13, 2006 5:42 pm

The best way would be to automate some plug-in's Out Gain setting via MIDI CC (or through the plain VST automation) and then render it down to WAV and see when the automation kicked in. The easiest benchmark would be a noise sample.

I just do not know which 'latencied' plug-ins support MIDI CC.

Anyway, I now think it may not be possible to measure this behaviour easily... Some plug-ins may catch the MIDI CC and adjust input gain where latency is zero, and then introduce latency on some later internal processing steps...

So, for the start I will be assuming no hosts do such compensation for the plug-in.

How hosts handle MIDI data and plug-in latency?