It seems that some of us, including me don't fully understand or are even aware of how Pro Tools' dual low latency buffer introduced with PT11 works. I'm wondering if people are being fooled into using lower buffers than their system or PT session can cope with because of this?
In another thread, (
http://duc.avid.com/showthread.php?t=390774 ,) there is mention of an Avid video showing 99 instances of Mini Grand running. It definitely rings a bell with me. In the same thread there was talk of how Pro Tools dual low latency buffer works. I couldn't find any reference to the 99 Mini Grand instances but I did find an old video by Avid explaining exactly how the dual low latency buffer works. Since this is OT in the original thread I've started this one.
The video is here:
https://youtu.be/6JzwngQbgHE - The info is 2'19" in.
I got it
completely the wrong way round in the original thread linked to above. It seems that tracks in playback mode are in a permanent high buffer state which the user has no control over. Only Record enabled or input monitor enabled tracks use the buffer the
user sets in Playback Engine. This obviously explains why I often get BIG jumps in CPU usage when I record enable a Kontakt instrument, especially ones with high polyphony counts and complex scripting.
Getting back to the 99 instances of Mini Grand. I've just run a test and got 110 individual instances of Kontakt, (each using one instrument - the factory library Grand Piano.) With a buffer of 128 in PTHD 12.6.1 and OSX 10.12.3, CPU usage was reasonably stable hovering at the lower range of 48 to 60%. Each of the 110 instances maxed at 30 voices or 3300 voices of polyphony. It seemed stable too. (I got up to 130 instances but then started getting a few -9171 and -9173 errors.) The weird thing is, there wasn't much apparent difference in CPU usage when a track was recorded to and I went nuts bashing away on a MIDI keyboard. Maybe the instrument in question wasn't CPU demanding enough but I
was running a heap of instances.
(BTW, I tried the exact same thing in Logic. Again, 110 instances although Logic's CPU meter looked to be running higher, (more stable admittedly.) OSX's Activity Monitor also showed surprisingly similar results. Both Pro Tools and Logic used very similar amounts of RAM - around 11GB.)
SO... In theory and according to Avid's video, playback is
always at a high buffer setting internally preset by Pro Tools. It's only the record enabled/input monitor enabled tracks that are affected by the user buffer setting in Playback Engine. The thing is, to me it often doesn't
feel like that is actually what is happening. I sometimes have to increase the buffer when VI and VE Pro polyphony and CPU usage gets above a certain level to stop pops and clicks. Why do I need to do that if PT is always running at a high buffer during playback?
As an aside - I felt that with PT11, given the same buffer settings as pre-AAX versions of PT, latency was better at higher buffer settings. Personally, I find a buffer of 256 or even 512 is quite playable for most VI's (not Maschine!) I didn't in previous versions. Overall system delay is usually more of a concern for me. (I can't get system delay as low with HDX than TDM. I'd like to be proved wrong but it seems to me the cause is that I have to run a lot more plug-ins natively because there's no HDX version.) ...But I digress.