DSPs are slowly becoming a staple of every modern audio product, so what exactly is a DSP? Why are they important, how do they work, and how do they affect your listening experience?
What Is a DSP?
DSP is an acronym for Digital Signal Processor. As the name implies, a DSP is a microprocessor specifically designed for audio signal processing. A DSP is basically a CPU optimized only to solve audio processing problems. And just like a CPU, DSP chips are essential pieces of audio hardware that make digital audio manipulations possible. DSPs have become so important that your audio equipment is likely integrating one or a few DSPs within their circuitry.
Common DSP Uses
DSPs are used in all kinds of daily audio electronics. To understand how impactful DSPs are to your listening experience, here are a few DSP applications you’re already using:
How Does a DSP Work?
All digital data, including digital audio, is represented and stored as binary numbers (1s and 0s). Audio processing such as EQ and ANC requires the manipulation of these 1s and 0s to achieve wanted results. A microprocessor such as a DSP is required to manipulate these binary numbers. Although you could also use other microprocessors like a CPU, a DSP is often the better choice for audio processing applications.
Like any microprocessor, a DSP uses a hardware architecture and an instruction set.
Hardware architecture dictates how a processor operates. DSPs often use architectures such as Von Neumann and Harvard Architecture. These simpler hardware architectures are often used in DSPs as they are capable enough to do digital audio processing when paired with a streamlined Instruction Set Architecture (ISA).
An ISA is what determines what operations a microprocessor can do. It is basically a list of instructions tagged by an operation code (opcode) stored in memory. When the processor calls for a specific opcode, it executes the instruction the opcode represents. Common instruction within the ISA includes mathematical functions like addition, subtraction, multiplication, and division.
A typical DSP chip using Harvard Architecture would contain the following components:
Program Memory-Stores instruction set and opcodes (ISA) Data Memory-Stores the values to be processed Compute Engine-Executes the instructions within the ISA together with the values stored in data memory Input and Output-Relays data in and out of the DSP using serial communication protocols
Now that you are familiar with the different components of a DSP, let’s talk about how a typical DSP operates. Here is a basic example of how a DSP processes incoming audio signals:
Step 1: A command is given to the DSP to process the incoming audio signal. Step 2: The binary signals of the incoming audio recording enter the DSP through its input/output ports. Step 3: The binary signal is stored in data memory. Step 4: The DSP executes the command by feeding the compute engine’s arithmetic processor with the proper opcodes from program memory and the binary signal from data memory. Step 5: The DSP outputs the result with its Input/Output port to the real world.
Advantages of DSP Over General-Purpose Processors
General purpose processors like the CPU can execute several hundred instructions and pack more transistors than a DSP. These facts may raise the question of why DSPs are the preferred microprocessors for audio instead of the bigger and more complex CPU.
The biggest reason DSP is used over other microprocessors is real-time audio processing. The simplicity of a DSP’s architecture and limited ISA allows a DSP to process incoming digital signals reliably. With this feature, live audio performances can have equalization and filters applied in real time without buffering.
A DPS’s cost-effectiveness is another big reason they are used over general-purpose processors. Unlike other processors that require complex hardware and ISAs with hundreds of instructions, a DSP uses simpler hardware and ISAs with a couple of dozen instructions. This makes DSPs easier, cheaper, and faster to manufacture.
Lastly, DSPs are easier to integrate with electronic devices. Due to their lower transistor count, DSPs require much less power and are physically smaller and lighter when compared to a CPU. This allows DSPs to fit inside small devices such as Bluetooth earphones without worrying about power and adding too much weight and bulk to the device.
DSPs Are Important Components in Modern Audio Devices
DSPs are important components of audio-related electronics. Its small, lightweight, cost-effective, energy-efficient properties allow even the smallest audio devices to offer active noise cancelation features. Without DSPs, audio devices would have to rely on general-purpose processors or even bulky electronic components that require more money, space, and power, all the while providing slower processing power.
