I am having a terrible time with the mixer in my orchestral template, so much so that it is almost unusable. My set up consists of a Mac Pro (early 2009 quad core 2.66GHz) but with 20 GB ram and two Mac Mini’s running VEPro. Each VEPro has two instances and each instance has 32 channels - 16 on midi in 1 and 16 on midi in 2.
In Dorico I have 4 Instances of VEPRo loaded and they are connected to 8 Vienna Ensemble Pro Event Inputs (2 for each instance). Instance 1 is Strings and has 2 Event inputs (16 midi channels each), Instance 2 is Percussion (2 Event Inputs) and you guessed it, the other two are for Woodwind and Brass. I have got Expression maps on each of the 8 Event inputs. Playback using the my custom Playing Techniques and my custom Expression Maps is working, albeit with judicious amounts of the ‘Nat’ or the ‘natural’ playing technique between each articulation change. This in itself is a major achievement considering that the overall playback functionality of Dorico is still in it’s early stages. I am pretty happy with this so far, having spent many hours getting to this point.
The mixer however is almost unusable. When I click the icon to show the mixer I get the beach ball for 5 to 10 seconds and every time I adjust or click on something like a fader, the same - 5-10 seconds. The mixer is showing 4 x 32 channel outputs - I guess this makes sense because I have 128 midi channels coming in from my 2 Mac mini’s, although in actual fact each instance really only comes in on a stereo input (1 & 2)…All I really need is 4 stereo inputs, one for each of my four VEPro instances. I have reduced the Channels on the plugins but that has not changed the mixer…I guess there is one fader for every midi channel entry in an expression map and as I have 8 expression maps with 16 midi channels each, that is what the mixer is representing. It is very, very slow however. I also have tagged on the end of the mixer some random channels from my orchestra (see attached .png) for which I have no idea how they got there. This mixer performance problem seems strange considering that I presume much of the playback engine and mixer came from Cubase - Apologies if I’m wrong. In Sibelius I have no such problem, although the VEPro outputs do indeed just show up as stereo outputs and therefore there are not 120 other vst instrument midi channels to process…This would seem to be the problem. Is there a way I can reduce the channel count and make the mixer more responsive, and where did these rogue outputs come from? (see Pic) I hope this all makes sense!
Thanks for any suggestions.
PS. Thought I had found a solution by changing the outputs at the VEPro end, but to no avail - deleted post but have reposted it.
I’m sorry to hear that you’re experiencing the problems with VEPro. We are very aware of the performance problems in the mixer when you have a large number of channels. Unfortunately there are no simple fixes for that at the moment. The root cause of this is the type of styled control in the programming framework is very slow to be created and to draw, and we have many of them (it’s the same control for the fader, EQ and send controls). We do have plans to rewrite this to make it much faster, but I’m afraid this isn’t something we’ll be doing imminently. We do hope to have better support for the larger orchestral libraries such as VSL/VE Pro in the future.
Dorico enables all audio outputs from a plugin, which means that you do have control over all individual audio outputs (and this is important for many users because then you can apply separate EQ/compression/plugins to each one), but we don’t yet have a means of restricting the ones that are shown. This means that you do have the extra channels in the mixer. Dorico has no way of knowing how sound is routed inside a plugin. eg HALion Sonic SE has 16 input MIDI channels and 16 output audio channels, and we know there’s a 1:1 correspondence between them. However, I think Aria has 16 input MIDI channels but 17 output channels; the first is the master and the other individual ones are offset by 1. Dorico labels the mixer channels assuming that each input channel maps to the corresponding audio channel, but if the plugin is routed differently then these channel labels will be incorrect. These are all things that we aim to improve in the future, but it will take some time to get there.
Yup I’ve mentioned previously here that I experienced similar mixer issues myself on a large film score I finished recently, and I’m running all my VST’s natively on one PC, not in VEPro. In fact it became so annoying waiting for the mixer to do anything that I basically ignored it in the end and even disabled the hotkey to avoid accidentally opening it (the defualt hotkey for the mixer is F3, but video is on F4 which I use a lot more).
I’ll definitely be looking forward to the day when the code for this can be rewritten to speed it up, it would actually be a useful feature for me then. 
I’ve implemented something this afternoon which should make it into the next update - this should hopefully improve the performance significantly if you have lots of output channels that you’re not using. There’s a new control on the Endpoint Setup Dialog (the dialog you access by clicking on the ‘*’ on the VST Instruments section in Play Mode) which will limit the number of plugin output channels shown in the mixer.