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-   -   HDX Delay comp weirdness on instrument tracks (http://duc.avid.com/showthread.php?t=403246)

ballandbiscuit 02-04-2019 04:25 AM

HDX Delay comp weirdness on instrument tracks
Hi Duc users,

I had a strange experience last time I used an HDX system. I plugged my computer (Mac Pro trashcan) into a Thunderbolt PCI chassis containing an HDX card.

I opened a session Iíd been working on natively, and immediately noticed some things not sounding right.

I had an instrument track with SoundToys Tremolator inserted after NI Massive. Tremolator was set to tempo sync, but was audibly late with respect to the click (I was using a sawtooth waveform, so it was immediately obvious that the sharp transitions werenít in time with the click). The amount that the tempo sync was out by varied according to the playback buffer setting. Everything else seemed to be working normally wrt delay compensation.

Routing was as follows: Instrument track -> Stereo bus (submix) -> Stereo bus (main mix bus) -> Analog output

The problem persisted even when I deleted every track in the session except for the above.

Luckily, the studio was using Apogee converters with Digi-Link cards - I was able to connect directly to the interfaces over USB, avoiding any problems.

But Iím a bit worried as Iím booked to do a session next week at a studio with HDIOs, so I wonít have any option other than to Thunderbolt into the HDX chassis.

Has anyone experienced anything like this when moving sessions between Native and HDX rigs? Anyone know of any workarounds, or system configurations which donít exhibit this behaviour?

Thanks in advance for any responses.

My system info should be displayed below - when I had the above problem I was running 2018.7 on High Sierra.

smokeydan 02-06-2019 04:35 PM

Re: HDX Delay comp weirdness on instrument tracks
Are you sure the tremolator was late rather than early?
I had an issue a few months ago, where I discovered that a Kontakt instrument was playing out of time if it was being triggered by its own internal step sequencer. It played in time if it was triggered by midi on the instrument track. This lead me to conclude that the instrument track was taking care of the delay compensation between the Midi and the instrument, rather than in the audio domain on the outputs of the channel. If I copied the instrument to an aux track instead, the delay compensation was dealt with correctly and the instrument played in time -
So I'm wondering, if your issue is related to this, and this difference in the behaviour of the Delay Compensation on Instrument tracks vs Auxes is the cause, whether you might get around it in a similar fashion - eg, run the instrument track through an aux and insert the tremolator on the aux??

ballandbiscuit 02-07-2019 06:46 AM

Re: HDX Delay comp weirdness on instrument tracks
Thanks for the tip smokeydan, and I think youíre right - it was early, not late.

Iím working at a studio with HDX next week, so Iíll try this.

Does anyone know if this is an acknowledged bug from Avid, and if thereís a plan to fix it in a future PT version?

Sent from my iPhone using Tapatalk

smokeydan 02-08-2019 03:56 AM

Re: HDX Delay comp weirdness on instrument tracks
Hi again - I just had 10 minutes to test this on our HDX system and its opened up a can of worms. Using pink noise generator on an instrument track, and a tremolator, comparing the tremolator on the instrument track vs on the aux. I used a square wave as this gave the clearest visual representation.
Using offline bounce - no difference between the two. Both in time.
Using online bounce - trem inserted on instrument track - in sync with click. trem inserted on aux - early compared to click.
recording audio onto audio track - trem inserted on instrument track - in sync with click. trem inserted on aux - early compared to click.

I've run out of time to explore further for now.
perhaps theres a preference somewhere thats affecting behaviour differently in your rig compared to mine.
But on my system, inserting the trem on the instrument track appears to work fine and is bang in time. There are various options in tremolator which affect the timing - I'm sure you've checked this, but I'm wondering if the "feel" knob has inadvertently been adjusted to push or pull?
I'm also quite alarmed that the behaviour is different comparing online and offline bounce modes.

ballandbiscuit 02-08-2019 11:04 AM

Re: HDX Delay comp weirdness on instrument tracks
Thanks for looking further into this Smokeydan. I never tried an offline bounce as it's not something I use very often. Regardless of the specifics, the fact that offline and online produce different results should be enough to flag this up as a bug for Avid.

I'm back on an HDX rig tomorrow, so I'll try and do some further testing (just saved copies of my sessions with all instrument tracks frozen just in case! :eek: )

Any Avid reps out there who can escalate this up the chain?

Edit: Just a thought, and I'll have a look at this tomorrow. I'm interested in seeing whether there's a difference in behaviour depending on whether the instrument track is routed to an aux, or directly to a physical output. Tracks in my sessions are rarely, if ever, routed directly to outputs. Things tend to go to a submix aux, mix bus aux etc etc.

I'm also gonna try some tests with other plugins that have tempo sync features. Who knows, it could be a SoundToys problem...

Edit 2: This would all be moot if we just had the option to run HDX rigs natively i.e. have the HDX card behave like an HD Native card with no extra features. Avid, if you're listening, this is a feature I'd find really useful.

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