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  #1  
Old 10-05-2007, 02:17 PM
MKZ MKZ is offline
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Posts: 45
Default Is there a delay/latency reference chart for LE ?

FIRST A QUESTION:

Is there an official delay/latency chart that I can print out for quick reference ?

I couldn't find one by searching the pdf manual for PT 6.4 (somehow I still have that on my comp and not the one for 7.3.... weird)

AND THEN MORE QUESTIONS AND STUFF:

I was testing the send/aux delays and I got a peculiar result...

1.) Audio Source being recorded to another track through a bus with a 44.1 kHz sample rate *

Source:Audio Track 1 w/ output: bus 1 ---->
Record Destination: Audio track w/ input bus 1

time difference between original source and the newly recorded:
1024 samples w/ buffer size of 1024 samples
256 samples w/ buffer size of 512
128 samples w/ buffer size of 256
64 samples w/ buffer size of 128

--------------
*to add to the confusion, I later found out that there's actually no delay when doing the above experiment... how ever, and this is where it gets weird for me at least, is that the above results were due to me having an aux track with the same bus input as the destination track (I had the aux track set up for test # 2. (below))
--------------

2.) Audio source being sent through an aux and then recorded on another audio track with a sample rate of 44.1 kHz

Source: Audio Track 1 w/ output: bus 1 --->
Aux Track w/ input: bus 1 and output: bus 2
Record Destination: Audio track w/ input: bus 2

time difference between original source and the newly recorded:
2048 samples w/ buffer size of 1024
512 samples w/ buffer size of 512
256 samples w/ buffer size of 256
128 samples w/ buffer size of 128

why is the buffer size of 1024 samples special? there's a clear trend going up from a buffer of 128 samples to 512 samples, but the trend is broken once you get to buffer of 1024 samples...

Do these results look right?


Also, is the send delay in HD systems always 10 samples, not depending on buffer size, as they suggest here:
http://www.songphonic.com/ProToolsTutorials
[EDIT: the place i'm referring to is under "2. Pro Tools :: Printing and Freezing Audio Tracks" #3 of the update: "# Enter this value (228) + 10 (for send delay) = 238 in the '+/-' field as a NEGATIVE number - ie -238. "]

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

I also found this:
(Latencies chart for analog inserts in LE w/ 002's)
http://www.elvenminstrel.com/recordi...tencychart.htm
and
http://www.elvenminstrel.com/recordi...auxlatency.htm

does it look right? I mean I just tested this as well and I get totally different results

Mine are
3166 (+- 2 samples) samples @ buffer size of 1024 samples and 44.1 kHz
1631 (+- 2 samples) samples @ buffer size of 512 samples and 44.1 kHz
864 (+- 2 samples) samples @ buffer size of 256 samples and 44.1 kHz

what's going on?

It also appears that I get the same results with 48 kHz

what am I doing wrong? or is the guy who posted that chart wrong? or is my system messed up? someone enlighten me, please

also, to hopefully clear things up a bit here's how I conducted this insert delay test:

-two audio tracks with the same snare hit on both, in the same exact place
-on one of them I added an insert (through an outboard device, but I also tested with just a cable going from the analog out 6 to analog in 6 )
-output of the source w/ the insert - bus1, output of the source track w/o an insert -bus2
-made two new "destination" tracks, one with bus 1 as input and one with bus 2 as input...
-recorded on to both destination tracks, measured the time differences between the two recorded tracks.

I must be missing something here..

Thanks...

oh yeah I'm running PT LE 7.3.1 with 002 Rack and a Mac G5
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  #2  
Old 10-05-2007, 04:03 PM
MKZ MKZ is offline
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Posts: 45
Default Re: Is there a delay/latency reference chart for LE ?

ok.. now i'm really losing it...

I ran some more tests and there's something really messed up happening with my pro tools busses....

i'll try and see if I can explain the problem later when i get a chance, but right now i'm just way too tired..

basically i get NO delay/latency (zero... not one damn sample) in some cases and sometimes i get the latency i've described above... i just cant wrap my head around what is going on here...i hope it's my mistake because that can be fixed... if it's something to do with my comp and pt... well, that needs money and this problem seems to be so weird that no one's gonna believe me unless they see for theirselves...
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  #3  
Old 10-06-2007, 10:43 AM
mixaudio mixaudio is offline
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Location: San Antonio, TX, USA
Posts: 402
Default Re: Is there a delay/latency reference chart for LE ?

Hi MKZ, I've been in the exact same situation. I have done some testing too, trying to come up with my own delay chart, and there are so many variables, that I've decided just to do a quick "track to track" bouncing test for each particular session, when I need to check for a specific amount of delay.

What you're getting might have to do with wether or not your "low latency monitoring" function is engaged or disengaged. Then, when you test different multiple HW buffer sizes, and this will also affect MIDI data, once it becomes audio, specially for any external MIDI synths.

If you set a MIDI track to play data onto an internal Virtual Instrument, you won't get an important amount of latency, since PT does some automatic compensation (PT does not do ADC for plug-ins, but it actualy does for MIDI running into VIs). Then, if you measure the amount of audio delay you get from your external MIDI modules or keyboards, when they are being triggered from MIDI tracks in ProTools, you'll notice that the audio is coming back to PT with a certain amount of delay that is prety much the amount of samples you have set in the HW buffer size. So, say for instance, that you have MIDI track for a steady, kick drum going to an external module, and your HW buffer size is set to the highest level (1024), and then you print the audio of this external MIDI kick drum onto a PT audio track, you'll be looking at a waveform that appears about 1400-1500 samples after the actual MIDI hits. This is an issue I've been hoping that will be solved soon, but haven't heard any specific comment from DigiTechSupp, and the only way to solve it is to set individual negative amounts of delay for MIDI tracks running to external MIDI synths (and leave MIDI tracks for internal VIs set to 0) either from the MIDI Realtime Properties window, or from the global MIDI delay window. Unfortunately, there is no "Realtime Properties" for audio tracks that will let you specify a negative amount of playback delay for audio regions (I would love that, even if it was not "automatic").

Then, you also have the variable of sample rate. You won't necessarily get the same delay amounts when working at 44.1K or 48K.

Also, if you need to print several MIDI tracks that run to independent external synths, but at the same time you need them submixed onto a single audio track, and you are not using an external mixer, then you'd have to hook them to PT analog inputs, and run them thru several Aux inputs which would be bussed digitally onto the destination audio track. Well, by doing this, you'll get a double amount of delay, because first, you'll have the MIDI data going to those synths being sent late (by the amount of HW buffer size), plus the latency created by bussing the Aux tracks to send the signal internally to the audio track where you'll be printing. So... with a HW buffer size of 1024, you'd be looking at your MIDI data becoming printed as audio, at about 2000 to 2500 samples late.

It's confusing... but the worse is that we are at the mercy of a glorious PT Engineering-Development Team to get a fix for this. Excuse the sarcasm, I actualy respect and love their work, but the reality is that we can not tell for sure of whether or not this is a priority for them or for Digidesign.

My couple of "ranty" 2 cents.

Rodolfo F.
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  #4  
Old 10-06-2007, 11:00 AM
mixaudio mixaudio is offline
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Default Re: Is there a delay/latency reference chart for LE ?


Well, not sure that I responded to the original question about an official latency chart.

I haven't heard of the existence of one, maybe because of so many variables involved, but I'd suggest to do a quick "track to track print" test on each particular session, as required. Don't forget that if you've set a lower HW buffer size, and after already done this testing, you require to change the HW buffer size to a higher level, then, you'll need to re-test, as all these delay amounts will become different. Also keep in mind that once you're on the final mix/bounce process, you should disable the "low latency monitoring" feature, so that everything that needs to go onto your main master, will really be included and processed.

Rodolfo F.
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  #5  
Old 10-08-2007, 01:32 PM
Gregor Gregor is offline
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Location: Gauteng, South Africa
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Default Re: Is there a delay/latency reference chart for LE ?

Hi

Yeah, this drives me nuts as well. I start getting "timing drift" in my tracks because I work on different tracks with different latency settings and then forget to change it back. So eventually I end up lining the recorded material up manually !!!!

This is the kind of problem computers were made for, there is a direct ratio between the buffer size and the latency added to the A/D D/A conversion time. Surely it wouldn't be so difficult to code this ?
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  #6  
Old 10-08-2007, 02:11 PM
sirgant sirgant is offline
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Default Re: Is there a delay/latency reference chart for LE ?

Don't know if this is what you need, but try this link:

http://www.elvenminstrel.com/recordi...002latency.htm


Hope it helps
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  #7  
Old 10-09-2007, 05:11 AM
Forum Member LE Forum Member LE is offline
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Posts: 395
Default Re: Is there a delay/latency reference chart for LE ?

Quote:
Hi

Yeah, this drives me nuts as well. I start getting "timing drift" in my tracks because I work on different tracks with different latency settings and then forget to change it back. So eventually I end up lining the recorded material up manually !!!!


That's like working with different tape speeds or sync codes.
Why the need to change your latency settings in the same project, what is the problem you are trying to compensate for by doing that?
I would deal with that instead.
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  #8  
Old 10-09-2007, 06:49 AM
sunburst79 sunburst79 is offline
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Default Re: Is there a delay/latency reference chart for LE ?

Quote:
Don't know if this is what you need, but try this link:

http://www.elvenminstrel.com/recordi...002latency.htm


Hope it helps
Excellent Link.!

About a year ago some one took the time to test the various plug in latencies for LE, Unfortunately my MacBook Pro actually crashed and took my bookmarks with it. I will eventualy dredge to posters screen name from the dark recesses of my memory and try to search and post the list.
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