PT's dual low latency buffer, 110 instances of Kontakt 'n stuff.

[Marsdy]

Originally Posted by midnightrambler

Dave

This AVID video must be BS? Or, I am doing something terribly wrong and/or misunderstanding that'a going on here....? -

I'm midway through a mix. As an experiment I've deliberately frozen all instruments and committed all Elastic, so only audio tracks are running. I've disabled Melodyne. There are no tracks in input monitor/record ready.


So, if I understand correctly, I should be able to set the H/W buffer to 32 samples and it not affect playback at all......? .... Have I missed something? - -

https://vid.me/OJnP

Exactly! Providing no track is record enabled or input monitored including VI's that is my interpretation of the video. It's not what some of us seem to be experiencing though. I'm not suggesting that Avid has been misleading us, more that the low latency dual buffer thing just isn't working as expected.

[guitardom]

Originally Posted by midnightrambler

BUT the AVID vid claims that you can set a low buffer without affecting other playback tracks at all....? "This allows the user to get the lowest possible latency without having to constantly adjust the buffer or the session"

We went through this with Brahath years ago in a thread. Compare the performance of PT10 at a low buffer with 11-12, its lightyears better now. This is because when recording, only the tracks in the record state have their buffer lowered. Regardless, CPU prioritization still has to happen. The CPU is sitting in a state of "ready to go" at a low buffer.

[dankin]

Originally Posted by TOM@METRO

The way I understand this, the playback buffer on all audio tracks in playback is internally set at the maximum buffer for the sample rate you are using. Tracks in Record are set by the user in the Playback Engine drop-down menu. For Instrument Tracks, both Playback and Record are set by the user.

When a VI track is Committed, it is treated like an Audio Track.

I hope this helps.

This is the way I've understood it as well. I think one of the big differences with logic, which also uses a dual buffer, is with Logic instrument tracks that are not record enabled also run at the higher buffer. This seems to be a source of confusion with PT, as some here are saying instrument tracks in PT also use the larger buffer when not record enabled, but in my experience that isn't true. If they did I think we would see a substantial increase in VI performance more inline with Logic (provided they also fixed those pesky 9173s). But on the other hand, midi timing in protools gets worse the higher the buffer is set, so if they were running at 1024 or 2048 the timing would probably be worse than it already is.

[Jon_Atkinson]

Originally Posted by Marsdy

Hey Jon

I'm pretty sure VE Pro and the VI's it hosts are treated just like any other VI in Pro Tools. I'm sure I'm getting the same apparent latency when playing the same instruments in Pro Tools as when it's hosted in VE Pro. I need to do some testing myself though!!!

As I said, it seems the super-low buffer is what you set in Pro Tools' Playback Engine. I've got it the wrong way round in the past. I always assumed that the Playback Engine buffer setting affected playback and that Pro Tools set a magical super-low buffer in the background. It's the other way round according to the Avid video! But given that the Playback Engine buffer actually does affect playback... weird!

It appears to be to do with Delay Compensation. From the manual:


"When a MIDI or Instrument track that is routing MIDI data to an instrument plug-in is record-enabled, Pro Tools automatically suspends Delay Compensation through the main outputs of the audio track, Auxiliary Input, or Instrument track on which the instrument plug-in is inserted. This allows for latency-free monitoring of the instrument plug-in during recording.

Delay Compensation for Instrument plug-ins works only when all MIDI and audio connections take place inside Pro Tools.
WhilePro Tools does not suspend Delay Compensation when you are using ReWire to connect software synthesizers and samplers in other ReWire client applications (such as Reason), Pro Tools cannot account for any latency within the ReWire client itself."

My experience of using VEPro (which I still love) in PT12 is that when using large track counts, trying to record a Superior Drummer track when there are loads of other tracks and plugins running is a non-starter due to latency.

If the plugins are hosted in PT (rather than VEPro) then it's perfectly possible to record with Superior (with next to zero latency) late on in a session when many other plugins are instantiated and VI's are running, so long as the output of the Superior Instrument track is routed to the main monitor outputs, not a bus.

It's kind of changed my workflow since PT12...

[midnightrambler]

Originally Posted by guitardom

Compare the performance of PT10 at a low buffer with 11-12, its lightyears better now.

I know it is. This is irrelevant to my point though.

Originally Posted by guitardom

This is because when recording, only the tracks in the record state have their buffer lowered. Regardless, CPU prioritization still has to happen. The CPU is sitting in a state of "ready to go" at a low buffer.

In which case, the AVID video is at best misleading, and at worst, completely wrong.

[TOM@METRO]

Originally Posted by midnightrambler

In which case, the AVID video is at best misleading, and at worst, completely wrong.

I think it would be fair to say that that video is a very simplified explanation of what's going on here. Probably to get people up and running, not to be a substitute for a white paper.

[midnightrambler]

Originally Posted by TOM@METRO

not to be a substitute for a white paper

[Marsdy]

Some information I'd forgotten about from the Pro Tools 11 What's New Guide.

Low-Latency Input Buffer
Pro Tools 11 provides a new low-latency input buf- fer. This ensures ultra-low latency record monitor- ing without sacrificing plug-in performance. The low-latency input buffer is automatically engaged while monitoring virtual instruments, and also for record-enabled tracks or input monitor–enabled tracks (Pro Tools HD only).

Note HD only! I have no idea if this has been added to PT12 native since, i.e. when all those HD features were added, (can't remember which version.)

[Marsdy]

Originally Posted by Jon_Atkinson

It appears to be to do with Delay Compensation. From the manual:


"When a MIDI or Instrument track that is routing MIDI data to an instrument plug-in is record-enabled, Pro Tools automatically suspends Delay Compensation through the main outputs of the audio track, Auxiliary Input, or Instrument track on which the instrument plug-in is inserted. This allows for latency-free monitoring of the instrument plug-in during recording.

Delay Compensation for Instrument plug-ins works only when all MIDI and audio connections take place inside Pro Tools.
WhilePro Tools does not suspend Delay Compensation when you are using ReWire to connect software synthesizers and samplers in other ReWire client applications (such as Reason), Pro Tools cannot account for any latency within the ReWire client itself."

My experience of using VEPro (which I still love) in PT12 is that when using large track counts, trying to record a Superior Drummer track when there are loads of other tracks and plugins running is a non-starter due to latency.

If the plugins are hosted in PT (rather than VEPro) then it's perfectly possible to record with Superior (with next to zero latency) late on in a session when many other plugins are instantiated and VI's are running, so long as the output of the Superior Instrument track is routed to the main monitor outputs, not a bus.

It's kind of changed my workflow since PT12...

I not 100% sure it's related to delay compensation here but I'm not denying your experience! Maybe it's a difference between native and HD? It might be VI dependent? I find Maschine horrible laggy at a buffer were Kontakt feels fine.

However, I'm doubting myself now so I've just run some tests to see what's happening here because I'm still using VE Pro all the time.
I created four tracks - all playing 4th notes of an identical click sample at the same level.
Track 1. An instrument track hosting Kontakt with an instrument loaded containing a click sample.
2. A committed version of track 1 i.e. an audio track.
3. An instrument track hosting VE Pro. In VE Pro I have Kontakt and the exact same click instrument as in track 1 loaded.
4. An audio track where I have imported the same click sample.

Any combination of tracks one through three pretty much completely null when one of any pair is phase reversed. (I say pretty much because I could just hear the click if I turned the monitors right up and stuck my ear by them! At normal to high listening levels I just couldn't hear anything.)

This was at any buffer setting from 64 to 1024. (It's VERY impressive that VI Pro can do this IMO!) Obviously at a high buffers set in Playback Engine I'm getting latency but at lower buffers down to 64 there's little or no perceivable latency. I also tested different combinations of the Kontakt and VE Pro tracks in record which according to the manual automatically suspends Delay Compensation which I had on during the tests. Whatever I did the Kontakt instrument track, the VE Pro track and the committed track all effectively nulled. (This was with VE Pro set to multiply the buffer by two.) Track 4 were I imported the click sample didn't quite null but I'm guessing this was because I couldn't quite match the level with the complex gain staging in Kontakt. 0.1dB increments weren't quite enough? I dunno.

Of course with just those four tracks and virtually no load on the CPU, I got a -9171 error. Yesterday when I had only those 110 Kontakt instances going, and a FAR higher CPU load I got no -9171 or -9173 errors.

[dankin]

Originally Posted by Marsdy

Some information I'd forgotten about from the Pro Tools 11 What's New Guide.



Note HD only! I have no idea if this has been added to PT12 native since, i.e. when all those HD features were added, (can't remember which version.)

But is this a "HD Software" feature, or "HDX hardware" feature? Also what part of that is tied to "HD" ? I use HD software with 3rdparty hardware. Input-enabled and record-enabled audio tracks and instruments definitely run at the user selected hardware buffer size. The only part that is questionable to me, is whether or not VIs that are not record enabled are utilizing the dual buffer. I personally don't believe they are. If they are, then Pro Tools VI situation is even worse than I think it is:) I've stated this before, but it would be nice if someone from Avid would clarify this.