Old 01-23-2018, 05:45 PM   #1
Cableaddict
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Default PDC in performance meter - HUH?

I won't use this thread to once again plead with the developers for a way to globally turn off all PDC.

Nope, not me, not here. I tried for about ten years & clearly they don't see the need for something so critical, so I will not raise the issue again. Nope. (g)
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But I have a question about the PDC read-out in the "performance meter."

In my main "Live Performance" session, I have (of course) laboriously defeated PDC in every plugin GUI window. Yet, in the "performance meter" It still shows two tracks with 512 samples of PDC each.

That's a whole lotta' delay, and I don't hear / feel it. (I don't think.)

So:

* Is this a bug in Reaper?

* Does Reaper show total "theoretical" PDC, even when it's been turned off in the track?

* Is this perhaps a bug in the individual plugin's reporting system?

-------------------

FWIW, one of these tracks showing 512 samples includes Kontakt, though other tracks with Kontakt do NOT have any PDC show in the performance meter.
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Old 01-24-2018, 01:38 PM   #2
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Bump.


Nobody knows?
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Old 01-24-2018, 02:05 PM   #3
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Can't confirm this (5.70 x64).
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Old 01-24-2018, 06:08 PM   #4
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Just so you know: at 44.1KHz that's apx. 11ms (and 5.3ms at 96KHz). So you might not feel it or notice it even if it does exist.
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Old 01-24-2018, 08:18 PM   #5
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Quote:
Originally Posted by JamesPeters View Post
Just so you know: at 44.1KHz that's apx. 11ms (and 5.3ms at 96KHz). So you might not feel it or notice it even if it does exist.
James, you're not alone in feeling that way, and I appreciate the thought, but I cannot agree. I fight for every ms.

Most good musicians tend to start to notice a problem around 7-9 ms. On a drum track I can consistently tell when the snare or hats have been move by 2 ms. (So can many other engineers)

I'm currently running at 88.2K, and my nominal audio "full" throughput is about 5 ms, so this would be a HUGE problem. I haven't had time to check if it's actually happening, but again, it doesn't feel like it. More like the readout is wrong.
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Old 01-24-2018, 08:19 PM   #6
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Quote:
Originally Posted by Dstruct View Post
Can't confirm this (5.70 x64).

Thx.

Did you try it with Kontakt?

How about Amplitube?
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Old 01-25-2018, 04:45 AM   #7
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Tested with Voxengo Elephant.
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Old 01-25-2018, 07:34 AM   #8
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I don't think PDC affects live monitoring. In other words, even if you turn off PDC, an audio signal still has the latency created by your interfaces audio buffer and the latency created by the plugin's buffer.

This is why to reduce latency people try to use the smallest audio buffer possible and plugin's that have "zero latency".
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Old 01-25-2018, 07:59 AM   #9
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AFAIK, PDC can most certainly affect live processed tracks... If the plugin asks for say 1024 samples PDC, you won't just get a 2x64 sample delay live processing. That is to say if the live signal passes through that plugin.
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Old 01-25-2018, 08:39 AM   #10
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Quote:
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AFAIK, PDC can most certainly affect live processed tracks... If the plugin asks for say 1024 samples PDC, you won't just get a 2x64 sample delay live processing. That is to say if the live signal passes through that plugin.
Yes, live signal passes through the audio buffers AND the plugin buffers so you get those delays.

So how does PDC affect live tracks then? Does turning off PDC remove any other buffers? If not, how could it affect live tracks? There's no change in the performance view of when you turn it on or off.

Not trying to argue, just curious because the menu item is "Preserve PDC in recorded items"

The only thing I can think of is if you had 2 live tracks, one with no plugin (no delay) and one with big plugin delay Reaper may add delay to first track so that two tracks output in sync. I haven't experimented to see if it does that.
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Old 01-25-2018, 11:22 AM   #11
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Quote:
Originally Posted by gkurtenbach View Post
Not trying to argue, just curious because the menu item is "Preserve PDC in recorded items"
I don't know as I've never needed to use it, but I imagine that it makes sure any recorded track is properly aligned with the playback tracks that were running while recording it.

Imagine the situation that you have already recorded tracks and have PDC on the output, then the newly recorded live monitored track would probably be offset by the same amount of PDC. So my guess is this answer, just too lazy to open the manual If I'm wrong, then someone please correct me
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Old 01-25-2018, 06:15 PM   #12
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Quote:
Originally Posted by gkurtenbach View Post
Yes, live signal passes through the audio buffers AND the plugin buffers so you get those delays.

So how does PDC affect live tracks then? Does turning off PDC remove any other buffers? If not, how could it affect live tracks? There's no change in the performance view of when you turn it on or off.

Not trying to argue, just curious because the menu item is "Preserve PDC in recorded items"

The only thing I can think of is if you had 2 live tracks, one with no plugin (no delay) and one with big plugin delay Reaper may add delay to first track so that two tracks output in sync. I haven't experimented to see if it does that.
I just tried this experiment and Reaper does not add any delay to sync the tracks.

Plus, toggling PDC does not change any latency.

So to the original poster, "Preserve PDC in recorded items" being on or off has no effect for live monitored tracks.


* Is this a bug in Reaper?

Nope

* Does Reaper show total "theoretical" PDC, even when it's been turned off in the track?

Yes.

* Is this perhaps a bug in the individual plugin's reporting system?

Probably not.

* FWIW, one of these tracks showing 512 samples includes Kontakt, though other tracks with Kontakt do NOT have any PDC show in the performance meter.

Kontakt 5 shows a plugin delay of 0 for me. Maybe there's other plugs on that one track.
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Old 01-25-2018, 08:04 PM   #13
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gkurtenbach, thanks for that thoughtful reply & test.


I'm still not 100% convinced that there would be no added latency, in ALL situations, but have to test for myself to see. For instance, if the session is in record-mode, (Which mine always is during a performance) then any tracks NOT in record, if they have large latency plugins that have NOT had their PDC turned off, should theoretically be delaying the entire session. If they didn't, then your recorded tracks would be out of sync with your live vocals. (I think. This makes my head hurt.)

So you MAY be correct and this is a non-issue, but I suspect there are situations where it's a problem.

If it wasn't, then why would we have the option to defeat PDC (sadly, only on a plugin-by-plugin basis) at ALL?
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Old 01-25-2018, 09:28 PM   #14
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Quote:
Originally Posted by Cableaddict View Post
gkurtenbach, thanks for that thoughtful reply & test.


I'm still not 100% convinced that there would be no added latency, in ALL situations, but have to test for myself to see. For instance, if the session is in record-mode, (Which mine always is during a performance) then any tracks NOT in record, if they have large latency plugins that have NOT had their PDC turned off, should theoretically be delaying the entire session. If they didn't, then your recorded tracks would be out of sync with your live vocals. (I think. This makes my head hurt.)

So you MAY be correct and this is a non-issue, but I suspect there are situations where it's a problem.

If it wasn't, then why would we have the option to defeat PDC (sadly, only on a plugin-by-plugin basis) at ALL?
Great question, what is the use of PDC, or rather not using it? Yes, it makes my head hurt too Here's what the reaper manual says:

"3.27 Preserve PDC Delayed Monitoring in Recorded Items

If you are monitoring audio on an armed track against previously recorded tracks any of which uses a plug-in that has latency (such as, ReaFir) this will cause the output to be delayed. In this case you may wish to have the recorded output sound exactly as you are hearing it while recording. For example, you might be playing the notes early in order to make it sound right.

With this option on, it will play back the same way you heard it as you played it, with the option off it will be earlier (as the PDC of the plug-in will take effect)"

I can barely play notes on time let alone early to compensate for a plugin's delay! But that sounds like the use case.
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Old 01-26-2018, 01:43 AM   #15
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"3.27 Preserve PDC Delayed Monitoring in Recorded Items

If you are monitoring audio on an armed track against previously recorded tracks any of which uses a plug-in that has latency (such as, ReaFir) this will cause the output to be delayed. In this case you may wish to have the recorded output sound exactly as you are hearing it while recording. For example, you might be playing the notes early in order to make it sound right.

With this option on, it will play back the same way you heard it as you played it, with the option off it will be earlier (as the PDC of the plug-in will take effect)"



^ I couldn't translate that into actual English with a gun to my head.

Seriously.


It also doesn't address the case in which some tracks are in playback mode, but no actual audio has been recorded.
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Old 01-26-2018, 08:07 AM   #16
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Here's what you guys want to understand...

Some musicians adjust their timing in real time by using what came back out of the monitors into their ears - in other words they hit the note and wait for that return through the entire chain as their guide as to when to hit the next note.

Other musicians do the opposite, they use the vibration they feel in their hands (when they actually play the note) as their point of reference for timing the next note and ignore the small difference in the monitors.

The latter foils PDC when monitoring and recording a live track, causing the result to be overcompensated aka the player compensated, then PDC compensated again. That's really all that statement in the manual is attempting to say. The most important thing is to understand how YOU adjust your timing on the fly and then choose the appropriate PDC setting (on/off) to match, because the right setting is different for each person based on how which cue they use, so there is no right setting for all situations hence the reason for having the setting to begin with.

Last edited by karbomusic; 01-26-2018 at 08:13 AM.
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Old 01-26-2018, 06:41 PM   #17
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I...... can't go along with all that, Karbo. "Playing by feeling" or whatever is a recipe for disaster. Your fingers get tired, your voice wears out fast... No one should ever have to compensate when tracking.


Regardless, this is how it used to work in Protools:

PDC was of course used when mixing, to keep everything aligned.
When recording, you would typically still keep it on, but on any track that was put into record, all PDC for plugins on THAT TRACK was automatically defeated. (until you take it back out of record.

Thus, you are playing / singing in real-time, (as fast as you can get your HW buffer, etc) even if there is tons of PDC on the already-recorded tracks.

The only reason, back then, to ever turn PDC off (which was done GLOBALLY) was to save cpu cycles.
And back then, for some folks, that was indeed an issue.
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When I first started using Reaper, maybe 5-6 years ago, this did not seem to be the case, so I got into the habit of manually turning everything off. I don't even bother to switch it back on, since there's no global control. I just live with it.


Now, I have no idea what Reaper's doing these days. Gotta' do some testing as soon as I can find the time.
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Old 01-26-2018, 07:14 PM   #18
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Quote:
Originally Posted by Cableaddict View Post
I...... can't go along with all that, Karbo. "Playing by feeling" or whatever is a recipe for disaster. Your fingers get tired, your voice wears out fast... No one should ever have to compensate when tracking.
It doesn't matter if you go along with it or not, that's how it actually works. It also in no way suggests you have to play differently, but it is critical to know which one you naturally do and check the right setting to match that if you have a concern - that's it. If you never know, you'll always be chasing this dragon and/or experience the frustration and confusion that goes with it for no reason - especially now, because you now know.
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Old 01-27-2018, 07:45 AM   #19
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Thanks karbo. Yeah, "Preserve PDC Delayed Monitoring in Recorded Items" is tough to understand. As you can see from this thread, some folks think (hope) it turns on/off or reduces plugin latency during live monitoring which it does not.

Your explanation of why its needed by some an not by others is really helpful.

Personally, I find it almost impossible to play a little ahead of the beat to manually compensate for plugin delay. So I've never used "Preserve PDC Delayed Monitoring in Recorded Items".

CableAddict: I don't use protools but in Reaper "Preserve PDC Delayed Monitoring in Recorded Items" has no effect on cpu cycles since it really just determines if Reaper moves newly recorded items backwards in time by the amount of the plugin delay for the track. That wouldn't consume CPU cycles.
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