Random transient mutes on tracks in Playback and Bounce

[Stormfront]

We've had PT12 running for about a year with no problems but yesterday had this on a simple Session with just 2x audio guitar tracks, 1x audio vox track and 2x stereo MIDI/Instrument tracks (our system is strong so no possible resource issues):

When Bouncing a mix offline, upon playing back the Bounce the lead vocal track has random transient mutes i.e. the track plays back throughout the song 98% perfect but about 3 times during the song the lead vocal disappears for maybe 1 or 2 seconds before fading back into the mix?

Upon re-Bouncing we received a perfect mix, but then upon 4 more tweaked Bounces these mutes would occur again - never in the same place on the track, and with other Bounces in between coming through fine??

The random mutes also were occuring in the track during Playback once we delved deeper to see what was happening - while the mute was occuring the track was certainly playing, certainly showing content at that part of the track, and the on-screen meters were firing indicating the audio was playing back and this was happening in the middle of a vocal line i.e. not necessarily related to any fades or other issues apparent to us.

The Session has no automation - and we subsequently tried Consolidating the original edited vocal track into a single track but the random transient mutes continued to occur right there in the middle of content (or not occur just as frequently).

We tried restarting the Session but the fault continued to appear, we tried restarting PT12 but the fault continued to appear, we then rebooted the whole system and seemed (though we only ran one Bounce out as we'd wasted so much time trying to simply Bounce the song by now) to have a clean result.

We just cannot think what is causing this so any help or experience wth it would be gratefully received - we did move straight from PT 8 to PT12 so have we missed something settings-wise along the way?

[Stig Eliassen]

Had the session been open (possibly idle) for a long time? I recently had a ref track play back randomly even though the track was muted.
I had left the session open over night, and continued working on it the next morning. Did a reboot, and all was good again.

PT doesn't seem to like sitting idle over longer periods...

[Stormfront]

Yes we have also noted the tendancy of PT to go to sleep and not entirely wake up, but like you said - a restart always fires it up again.

But this is not that - the Session in question had been actively worked on for about 30 minutes prior to performing the first Bounce - to that point all Playback had been fine so it was only upon playing back the Bounce that the random transient mutes on the lead vocal became apparent.

At that point we then re-Bounced and had a perfect result without mutes, then tinkered a few levels and Bounced a third time to find the random transient mutes occurring again but in different places to where they'd been the first bounce.

At this point we went into the vocal track in-Session and found mutes occuring at random places throughout the track while it was Playing back from the Edit window, and these muted points changed from play to play. At all times the track showed full content and meters were firing indicating there was playback in the silent sections - and the mutes only last for about 2 seconds at a time.

The silent sections were also NOT aligned with any vocal segment or fade zone - in fact they'd occur right in the middle of a vocal audio section just like we'd at that point we'd toggled the Mute button on that track during playback?

We then tried a 4th Bounced and had mutes in different places again, then the 5th Bounce was fine.

We have noted with MBox Pro it occassionally flips output to the PC's system audio instead of its own, and have also noted a (possibly standard setting but if not a fault) where every now and again either the Headphones A and/or B feeds are mysteriously re-routed away from the Analogue/Main 1-2 - so we have to go into the MBox software controller and re-assign the Headphone sends. Only happens once every few months but still bizarre.

Also to note - certainly restarting both the Session and then PT12 didn't eliminate the issue - though (so far fingers crossed!) a whole system reboot did eventually give us a clean result.

If we possibly can this weekend we're trying to find downtime to test the Session again to see if the issue raises its head again......

[Stormfront]

So we've re-opened the Session several times since and continue to have the random transient mutes occuring in the vocal track - also have confirmed absolutely no Mute (or any other) Automation in play.

Mutes continue to happen in Playback and Bounce, different parts of the now Consolidated entire vocal track each time.

Have tried systematically removing Plugins on the vox track - possibly the only third party compressor could be causing the issue but it's impossible to tell yet as there's no guarantee that just because last time it played with that Plugin disabled, that the next time it won't fail again with that Plugin still disabled?!

Incredibly frustrating and time wasting - at present we've gone back to Real Time Bouncing to monitor the result.

[Stig Eliassen]

Which exact version of PT is this? What happens if you don't use the Mbox?

[Stormfront]

We've got Pro Tools 12.2.0 running on Windows 7 Professional SP1.

As we've disabled our system sound we can't run sound on our studio PC without the MBox Pro - that's mainly because the MBox Pro has another known transient glitch where it chooses to randomly toggle the Session Playback engine to the Windows system sound. So we disable system sound and it seems to stay stable since then with only the MBox Pro connected and on.

It's so hard to troubleshoot because it's random and transient so may, or may not happen on any particular playback. Just ran it again with the "suspect" third party Plugin back on and ran perfectly so who knows?

Our biggest concern is that in a busier mix we wouldn't necessarily even notice a second or two of a track or two going missing here and there - it's just that this is a simple "guitar + 1 vocal + 2 synths" mix and being the vocal you can't miss it when it disappears.

[soybalm]

If you are rendering offline, it could be one of your "look ahead" compressors. You did try rendering in real time? I had that problem with Nuendo where the Waves L2 wouldn't work right unless it rendered in real time. It sounded really pumped as it was making up quite a bit of gain. It kinda bums me out that this can even happen with Pro Tools but I bet it's a plug-in somewhere.

[Stormfront]

Thanks for the feedback everyone - yes at present our only "best guess" is the "look ahead" third party compressor on the track - in the next few days we'll go back and do a "real time" Bounce with the third party compressor on and see what happens.

Initially because the affected vocal track comprised scores of edited sections we thought maybe a few sections were suffering a "shouldn't be hapening" attack/release issue but then when we consolidated the track it still happens, and happens in a different place every time.

But so far with that third party compressor inactive we haven't (yet?!) replicated the issue - and the fact it happens in Playback AND Bounce seems to suggest a processing issue of some kind.

So disappointing when clearly our 32GB RAM system should be more than able to run anything it wants (and copes with HD video clips no worries) so PT12 seems to have an issue.

Our previous 3GB RAM system was a "plastic blue" MBox 2 Pro with PT8LE and it never flawed once, and regularly ran mixes of 24+ tracks with scores of MIDI Instruments and track Plugins without any problems, including a myriad of third party plugs.

Also frustrating that our beloved Massey plugs seem destined to never go to AAX - they were a staple here.