Understanding CPU Management For Digital Audio Recording
Introduction
In this article I will be discussing CPU management for digital audio recording. We’ll be going through the core logic (puns slightly intended) of this subject using Logic Pro X as my point of reference for all examples. The theory behind these concepts and my efficiency management approach can translate to any digital recording platform — just reference your software manual to find these settings in your DAW of choice.
Core Concepts:
- Understanding Your Computer
- Audio Buffer Size
- Settings for Recording and Mixing
- Monitoring CPU Usage
Understanding Your Computer:
First things first: It’s important to acknowledge that if you’re running large sessions your computer WILL max out at a certain point. Even the most powerful computer in the world can eventually spit out these errors:
If you’re not sure what your computer has under the hood you can navigate to About This Mac:
Processor:
Your computer processor is what drives the entire machine. Processors can have one or many cores which perform tasks based on the data they are given. For recording, the DAW tells your processor to record audio to the hard drive, play back audio already recorded and run powerful software instruments and plugins (just to name a few) all at the same time.
Memory:
In a computer we have Virtual Memory and Random Access Memory. When the Central Processing Unit is processing a lot of data, it uses RAM to store data temporarily. The more RAM you have the more efficiently your computer can store this data so it’s ready for the CPU. Audio recording uses a lot of RAM due to the constant reading and writing of audio files.
If you’re in the market for an upgrade be sure to Google your machine model to see what it’s capable of. If you’re looking to buy a new machine, you will thank yourself later if you load up on processing power and RAM storage. Lastly, a Solid State Drive is a nice to have. Drive upgrades are last on my list because HD space is cheap these days and the easiest to upgrade.
Audio Buffer Size:
Most of us are using external sound cards/audio interfaces that give us additional i/o options and other goodies like high gain mic preamps/direct inputs. Sound cards have A to D and D to A converters that take analog audio signals and turn them into binary. Similar to how our software communicates with our CPU, our computer also talks back and forth with our sound card.
Sound cards need time to take in and process signals to make the A/D and D/A roundtrip. This is called the Buffer Size. In Logic X, we have control over how fast our sound cards process the audio. Logic Pro X>Preferences>Audio>Devices
Here, we have six choices: 1024, 512, 256, 128, 64 and 32 samples. The higher we set this number, the more time the audio interface has to process audio as it comes in and out. The lower this number is set, the more strain there is on the CPU to pick up the slack which decreases the amount of processing power for plugins, software instruments, etc.
Settings for Recording and Mixing:
The benefit of a low buffer size: Minimal to no noticeable latency when recording
The benefit of a high buffer size: Max efficiency for DAW workload distribution to your computer processor cores
The key is to know when to set the buffer size to these specific values. A general rule of thumb is to set a high i/o buffer size when mixing and a low buffer when tracking.
Most DAWs offer a low latency monitoring mode that temporarily lowers the buffer size behind the scenes.
There are a few different ways to access this feature in Logic X depending on how your settings are configured. Here a few screen shots to get you in the right direction:
Note: In Logic X, some plug ins will temporarily turn off when this setting is engaged
The bigger your session gets in terms of track count and plug in usage the more latency you will experience. Low latency mode can be your friend but if you forget to turn it off you may start experiencing clicks, pops or system overload messages as your session grows.
Monitoring CPU Usage:
So how can we monitor the efficiency of our computer while it processes all of our audio data?
Luckily in Logic X there is a CPU/HD monitor that displays the core distribution of your machine. By default this meter is not visible. To show it, right click on your transport bar and click “Customize Control Bar and Display”. From there you can check “Load Meters (CPU/HD)”:
It’s nice to take a glance at this meter as your session grows to have a handle on how much horsepower you have left to work with.
Conclusion:
This is just an introduction on how you can maximize your computers capabilities when recording music in a digital domain. Using external hard drives to store and run your sessions from, using audio interfaces with built in DSP and configuring DAW templates are some other possibilities I will talk about in future posts.
All computers have their processing limit and digital audio recording uses up a lot of resources but with a few simple tricks we can operate larger sessions and limit the “system overload” errors that hold back our creativity and workflow.
Happy mixing!
Sean Kimzey
Full Stack Web Developer and Audio Engineer
