Question 2 for Digi Tech Support

[Pro Toolian]

So yesterday I was asking about latency with regards to the Mbox and Digital spdif inputs.

Here is what I need to know.

1. What is the minimum amount of latency I can get with Mbox using my Apogee Rosetta via the spdif input on Mbox using the lowest buffer setting (128) and will it be low enough to do any tracking and overdubbing?

2. Does Digidesign not intend the digital inputs of Mbox to be used for tracking?

3. Is the lowest amount of latency on Mbox using the spdif input the same as the lowest amount of latency on Digi001 using it's spdif input?

4. If the lowest amount of latency on the Digi001 is less than the lowest amont on Mbox then why was the Mbox made that way? Why not the same as Digi001 via spdif input?

Thanks again for your time and patience.

[mattpete]

Pro Toolian,

Is your setup something like this?
mic -> mic pre -> rosetta --s/pdif--> Mbox

If so, try this:

1. Split your analog signal from your mic pre and send that into the Mbox analog inputs.
2. Record your tracks through Rosetta into Pro Tools like you normally would -- make sure to mute the rec-enabled tracks so you don't hear the latency.
3. Adjust the Mbox 'mix' pot to a desirable setting.

Voila, zero-latency overdubs with your favorite external A/D.

Oh yeah, don't forget to shift your newly recorded region earlier by 164 samples. (option-H)

Hope this helps,
-Matt

[SOR]

mattpete ,

What did you mean by "Oh yeah, don't forget to shift your newly recorded region earlier by 164 samples. (option-H)" in the previous post ?

are you stating that if you track through the SPDIF input, where will be a 164 sample delay in your regions?

how about Mbox's Mic/Line Inputs ? do there regions have a delay ?

can you please explain this to me further

SOR

[DigiTechSupt]

RE: 164 sample delay

-When you record into Pro Tools there is a latency of 164 samples. All tracks recorded into Pro Tools have 164 samples of latency, but you will not notice this with the first track unless you have a MIDI click, or a recorded click to play along with. Thus, when you record the second track/pass, you will hear latency when the two tracks are played together. Therefore, you will have to do the following:

1)After recording your second track/pass into Pro Tools, adjust the newly recorded audio track to compensate for the 164 samples of latency.
2) Select the second pass of audio with the Grabber Tool. Edit Menu > Shift. Click "Earlier" and type in 164 in the "Samples" field. Click "OK". Now, Pro Tools will locate the audio 164 samples earlier.
3) "Shift" each track or recorded pass backwards by 164 samples right immediately after recording. If you are stacking up tracks, you definately want them all to be in sync as each new one is recorded.

Now, you may ask, are all other passes 164 samples apart from each other too?

Not exactly. Each recording pass will be 164 samples behind everything already recorded. If you record one track at a time, and mute recorded tracks as you go along so you're only listening to the most recent track, then yes, your final track (say, 24) will be 23 x164 samples behind the first track, at least in terms of what you're hearing. Technically, the last track is still only 164 samples behind the first track but listening to these delays building up will cause your playing in time to the tracks to start falling behind noticeably.

So if you add one track at a time and listen to all previous tracks on each recording you'll be hearing:

Track 1: On time
Track 2: 164 samples behind Track 1
Track 3: 164 samples behind Tracks 1 and 2, so play in time to Track 1 you're off by 164 samples, but if you play in time to Track 2 you're 328 samples off.
Track 4: 164 samples behind Tracks 1, 2, and 3, but the delays build up differently depending on what track you play off of.

Brent

[Carl Z]

Curious, how many miliseconds is 164 samples?

[mattpete]

1000 msec
------------ X 164 samples = ~3.7msec
44100 samples

1000 msec
------------ X 164 samples = ~3.4msec
48000 samples

[mattpete]

1000 msec
------------ X 164 samples = ~3.7msec
44100 samples

1000 msec
------------ X 164 samples = ~3.4msec
48000 samples

[Nixo]

If I record the next track without monitoring by Protools, but through external hardware mixer, I need to compensate the latency in the same way ?????

[Skaberlakestudio]

Hey there
I think you have to compensate 164+ the latency you set on your buffersize(256,512) If you are listening to any tracks already recorded. [img]images/icons/rolleyes.gif[/img]

[mattpete]

The Mbox always has a total (analog out to analog in) latency of 164 samples.
I measured my MIXPlus system with 888/24 IO to be 81 samples.
On both systems, the total latency in terms of samples stays the same no matter the sample rate or the buffer size.
Let me say that again.

Sample rate and Buffer size DO NOT affect the total latency as measured in samples.

You can test this yourself.
1. Connect output 1 to input 2.
2. Play a very short signal out of output 1 and record it on another channel taking input 2.
3. Zoom way in and measure the distance between the same place in the waveforms. This is the amount of total latency in the system.

You can test the latency of any recording system this way.

-Matt