When you record audio into Pro Tools, the time it takes your computer to receive the input signal, record it, process it, and send it back out to an output is called latency. Latency values can be as low as zero or higher than 50 milliseconds on up, which is quite noticeable, and will most likely negatively affect your performance while recording. I'll show you why. I you go to Setup > Playback Engine, we can set the hardware buffer size, and this is a major determinant of what your latency is.
If we bring it down to the minimum, 32 Samples, that's really unnoticeable. I'm going to record-enable this base track. I am going to play a few notes, and you won't be able to distinguish when I actually hit the string and when the note comes back from Pro Tools. (Music playing.) However, if I change this H/W Buffer Size to 1024 Samples, now you are going to be able to hear the difference between when I actually strikes the note and when it comes back from Pro Tools.
(Music playing.) This latency can certainly affect your performance, and will most likely not enable you to play in time with the rest of the music. So that's why you want to reduce the latency, that is reducing the H/W Buffer Size, down to the minimum when you're recording. Those of you recording into a USB-powered interface, like an Mbox 3, can achieve zero latency monitoring by turning the Mix knob all the way to the left on the input side.
This routes the input signal right back out of the interface before it's even converted from analog to digital; thus there's no latency. On those USB-powered interfaces, to hear your input track along with the other tracks that have already been recorded into Pro Tools, you need to put the Mix knob into the middle. In this case, you'll hear the input signal with zero latency and the playback from Pro Tools, which will have a little bit of latency. With a small H/W Buffer Size, this is manageable. However with the larger buffer, the latency causes too much delay between the pre-recorded track and the track currently being recorded, which will negatively affect the timing of your recorded performance.
On some M-Audio and third-party USB devices, the Mix control is software driven. In this case, you can go to the Setup > Hardware and launch the setup application. In there, you'll find the controls to adjust the mix level. FireWire interfaces like the 003 and the Mbox 3 Pro handle digital audio and latency in a slightly different way. For those devices, the minimum latency is not zero; it's actually three milliseconds, because it takes 1.5 milliseconds to convert an analog signal to digital and another 1.5 milliseconds to convert it back from digital into analog.
This A to D to A conversion takes a total of three milliseconds. FireWire interfaces can utilize a feature called Low Latency Monitoring, which is turned on or off from the Options menu. It's right down here at the bottom. When it's on, the latency is three milliseconds. However, there are some accompanying limitations. All plug-ins and sends on record-enabled tracks are automatically bypassed, so when using LLM you can't record with any real-time effects on the record-enabled tracks.
Let me turn this on, and you will see what I mean. If I record-enable this lead guitar track, this delay plug-in will have to be bypassed, and it happens automatically. In practice, I've found that working with low buffer sizes is totally fine for recording even the most time sensitive material, and so I don't really use Low Latency Monitoring very often. Once you've done recording, you can go back to the playback engine and change it to a higher buffer size if needed. But when you're recording, I recommend knocking it down to the smallest hardware buffer size available. Now, you can record with Automatic Delay Compensation active as well.
Delay Compensation will be applied to all tracks in the session, except the tracks that are record-enabled. You can turn on delay compensation right down here. Pro Tools will tell you to open the Playback Engine dialog in order to enable Delay Compensation, and you can choose yes, of course. Here you can choose between None, Short, and Long. Regardless of what you choose, Pro Tools automatically compensates for any timing discrepancies between the material being recorded and the delay- compensated tracks.
When the newly recorded tracks are played back, they are correctly time-aligned with the other delay-compensated tracks. So, Pro Tools will manage the delay compensation for you automatically while recording, but it's up to you to manage the latency by adjusting the proper parameters shown in this video.
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