Matt explains the three primary computer resources as they relate to digital audio: CPU (processing power); RAM (short-term memory); and storage (long-term storage on a hard disk or SSD). Processing power is needed to use effect plugins and synthesized virtual instruments. Memory is needed especially for sampled software instruments. Storage needs to be fast to work with lots of audio tracks, and high capacity to have room to store those tracks.
- With digital audio, we rely on our computers to do an incredible amount of processing. Sometimes the computer can run out of one or more resources while trying to do all of that processing, resulting in slow performance or even crashes. A little knowledge goes a long way to help prevent that from happening. Let's explore the differences between the three main resources that a computer uses and how they affect your computer's performance with digital audio. I've simplified these into generalizations and rules of thumb.
The three main computer resources are processing power or CPU, memory or RAM, and Storage like a hard drive or solid state drive. Let's start with processing power. That refers to how much math the computer can do in a certain amount of time. Everything a computer does is math. When you move the mouse pointer, the distance you moves adds or subtracts numbers to the pointer's coordinates. When you type or read text, every letter is represented by a number, and when the computer draws the letter on screen, it looks up a bunch of other numbers to know what shape to draw.
And when you record and playback audio, the computer is the traffic controller for thousands or millions of numbers every second, and usually doing some kind of math on all those numbers. For example, turning a sound up or down in amplitude means multiplying or dividing every single sample. The computer's CPU or Central Processing Unit is what manages all these numbers. This computer's CPU is hidden behind this large heat sink. Here's what it looks like exposed.
A CPU has one or more cores where each core can work on a different math problem all at the same time. The processor also runs at a certain frequency, usually measured in gigahertz meaning billions of cycles per second. Each cycle computes part of a mathematical operation. The CPU's power is partly determined by the speed and the number of cores, but some models of CPU, especially newer ones, are more efficient. That is, the same math takes fewer cycles.
Because of that, different models of CPU can have different amounts of processing power even if they have the same number of cores and the same speed in gigahertz. In the digital audio realm, more processing power means the computer can handle a greater number of plugins. It also allows for effects that are more complicated in computer terms, that is. For example, a simple effect might be a single echo. In that case, the computer only needs to copy samples to create the echo, divide the copied values to make the echo quieter, and then, add the echo shortly after the original sound.
But to do automatic pitch correction, it has to do calculus, trigonometry, and other advanced math that uses much more processing power. Besides processing power, the other two main computer resources are memory and storage. Memory and storage are often confused with each other because both of them are places to keep information, but they behave differently, and they're used for different things. Memory refers to working short term memory.
It's very fast to access, but temporary. If the computer is turned off, the contents of memory are lost. Memory is also referred to as RAM which stands for Random Access Memory. Adding RAM can sometimes make your computer faster because if you don't have enough RAM to fit everything you're working on, the CPU has to work on one smaller piece at a time which slows it down. But if you already have enough RAM to fit everything, adding more won't make the computer any faster.
Your DAS documentation will tell you it's minimum RAM requirement. Unlike memory, storage is archival. That is, it's slower to access but permanent. Information stays there when the power is off. Storage refers to things like a hard disk which records information magnetically on spinning circular platters, an SSD or Solid State Drive which uses a different technology called Flash, USB drives, usually using a cheaper version of Flash, optical media like CDs, DVDs, and Blu-Ray discs, and of course older technologies like floppy discs and magnetic tape.
The size of the storage medium, the storage capacity, not the physical size, tells you how much information it can hold, measured in bytes. Each byte is made up of eight bits. Audio takes different amounts of disk space depending on the format. For example, at 48 kilohertz and 24 bits, audio takes more than eight million bytes or eight megabytes per minute per mono audio track.
Information on a computer is constantly moving back and forth between memory and storage. When someone talks about saving a document, it means copying it from temporary memory to permanent storage. Then you can use that memory for something else or even power down the computer without losing what you're working on which is safely in storage. Likewise, loading or opening a document means copying it from the slower permanent storage to the quick, temporary memory so the CPU can work with it.
This is simple enough with something fairly small like a word processing document where it makes sense to load the entire thing from storage into memory. But audio projects are quite a bit larger and more complex. Much of the time, when recording and playing back audio tracks, the audio files are streamed more or less directly to or from the hard disk. That means that the speed of your hard drive or solid state disk is a big factor in determining how many audio tracks you can record or play back simultaneously.
Storage and memory come into play for virtual instruments too, but in a different way. Some virtual instruments use samples. For example, a sampled piano where each time you press a key, it plays back a recording of a real piano playing that note. Long term storage, especially a spinning hard disk is often too slow to find and play back those samples in time to respond to your key presses. Especially if you're hitting a lot of piano keys at once.
In that case, it makes much more sense to load all those samples into RAM so that the computer has instant access to them at any time. Some software instruments use clever tricks to play parts of the samples from disk but in general, the amount of RAM you have determines how many different sampled instruments you can have actively playing at once. Not all virtual instruments use sample recordings. Instead of playing back prerecorded sounds in RAM, those instruments synthesize their sounds from scratch using math which means that instead of using memory or storage, they use the CPU's processing power.
One last note about storage. It's possible for a computer to have more than one hard drive or SSD. In that case, it makes a difference how you spread the work across drives. For example, if you have two drives, it would be most efficient to put your audio recordings on a different drive from your libraries of sampled virtual instruments. Keep in mind, using two partitions on one drive doesn't count for this. Only separate physical drives.
Let's summarize how the three main computer resources affect a DAS performance. Your CPU's processing power determines how many effect plugins or mathematically synthesized instruments you can use at once. RAM determines how many different sampled software instruments can be playing at once, and with storage, the speed of the drive determines how many audio tracks you can work with at once, and the size determines how much it can hold. With an understanding of the three main computer resources you can make informed decisions about computer hardware based on your specific needs.
The course starts with explanations of what sound really is and how we hear it, including discussions on frequency, amplitude, phase, and psychoacoustics. Matt explores analog audio signal path, explaining connections, gain staging, and metering. Next, he brings the audio signal into the digital domain, discussing analog to digital conversion, digital gain staging, file formats and compression, and dither.
Then the course digs into digital audio workstations (DAWs), explaining the concepts and misconceptions involved in digital recording systems. Matt describes how memory, CPU speed, and storage affect your DAW's performance, as well as how to manage computer resources and understand the plethora of file formats associated with digital recording. He follows with an overview of MIDI: how to generate, store, process, and communicate MIDI data. He wraps up with the audio processors that are often used for mixing in a DAW—including EQ, compressors, reverb, delay, and many others.
- What is sound?
- The three domains of sound: acoustic, analog, and digital
- The analog vs. digital signal paths
- Converting analog audio to digital
- Digital formats and data compression
- Understanding the five types of DAWs
- Recording performances with MIDI
- Mixing and processing audio with EQ, compression, and other effects