This document defines key terms and concepts used in BitPerfectCore and audiophile audio playback.
Audio playback where the digital audio data is passed to the DAC exactly as it exists in the source file, without any modification, processing, or conversion. Every bit matches the original.
The number of audio samples per second, measured in Hz or kHz. Common rates: 44.1kHz (CD quality), 48kHz, 96kHz, 192kHz, 384kHz.
The number of bits used to represent each audio sample. Common depths: 16-bit (CD quality), 24-bit (studio quality), 32-bit (floating point).
Hardware device that converts digital audio signals to analog signals for speakers or headphones.
Audio compression that preserves all original data. Formats: FLAC, ALAC, WAV, AIFF, APE, WavPack.
Audio compression that discards data to reduce file size. Formats: MP3, AAC, OGG, Opus. (Not supported by BitPerfectCore)
Standard digital audio format representing audio as a sequence of samples.
Alternative digital audio format using 1-bit samples at very high rates (2.8MHz, 5.6MHz, 11.2MHz).
Seamless transition between tracks with no silence or interruption, essential for albums and live recordings.
Taking complete control of an audio device, bypassing system audio mixing and processing.
Converting audio from one sample rate to another. Avoided in bit-perfect playback as it modifies the audio.
Temporary memory storage for audio data before playback. Prevents dropouts and glitches.
Time delay between audio processing and output. Lower is better for real-time applications.
Timing variations in digital audio signals. Can affect audio quality.
Audio distortion when signal exceeds maximum level. Should never occur in bit-perfect playback.
Available dynamic range before clipping occurs.
macOS framework for low-level audio hardware access.
Physical or virtual audio hardware (DAC, sound card, etc.).
Flow of audio data from source to device.
Callback function that provides audio data to hardware.
macOS audio processing plugin. Not used in bit-perfect path.
Resampling performed by the system. Bypassed in bit-perfect mode.
High-level audio API. Not used by BitPerfectCore (uses HAL instead).
Core component that orchestrates bit-perfect playback.
Component that sends audio directly to hardware.
Component that decodes audio files to PCM.
Component that configures device to match source sample rate.
Component that manages audio buffer allocation and queuing.
Component that enumerates and configures audio devices.
Component that handles seamless track transitions.
Component that reads audio file metadata (tags, artwork).
Audio reproduction without coloration or character. The goal of bit-perfect playback.
Audio reproduction with added character or modification. Avoided in bit-perfect playback.
Audio equipment or playback that doesn't add or subtract from the source.
Faithfulness to the original recording. High fidelity = accurate reproduction.
Level of detail in audio reproduction. Higher sample rate and bit depth = higher resolution.
Difference between quietest and loudest sounds. Measured in dB.
Range of frequencies a system can reproduce. Ideally flat (20Hz-20kHz for human hearing).
Measure of distortion in audio signal. Lower is better.
Ratio of signal to background noise. Higher is better.
Popular open-source lossless audio format. Supported by BitPerfectCore.
Apple's lossless audio format. Supported by BitPerfectCore.
Uncompressed PCM audio. Supported by BitPerfectCore.
Apple's uncompressed PCM format. Supported by BitPerfectCore.
DSD audio file formats. Supported by BitPerfectCore.
Lossless compression format. Planned support.
Hybrid lossless/lossy format. Planned support.
Embedded information in audio files (artist, album, title, etc.). ID3, Vorbis Comments, APE tags.
Code that can be safely called from multiple threads simultaneously.
Algorithm that doesn't use locks, essential for real-time audio.
Processing that must complete within strict time constraints. Audio rendering is real-time.
Behavior that is predictable and consistent. Required for audio thread.
Swift's asynchronous programming model.
Design approach using Swift protocols for abstraction.
Design pattern for providing dependencies to components.
Test of individual component in isolation.
Test of multiple components working together.
Percentage of code executed by tests.
- API - Application Programming Interface
- SPM - Swift Package Manager
- HAL - Hardware Abstraction Layer
- PCM - Pulse Code Modulation
- DSD - Direct Stream Digital
- DAC - Digital-to-Analog Converter
- ADC - Analog-to-Digital Converter
- FLAC - Free Lossless Audio Codec
- ALAC - Apple Lossless Audio Codec
- WAV - Waveform Audio File Format
- AIFF - Audio Interchange File Format
- THD - Total Harmonic Distortion
- SNR - Signal-to-Noise Ratio
- dB - Decibel
- Hz - Hertz
- kHz - Kilohertz
- MHz - Megahertz
- CPU - Central Processing Unit
- RAM - Random Access Memory
- I/O - Input/Output
- UI - User Interface
- UX - User Experience
- MVP - Minimum Viable Product
Last Updated: June 2026
Note: This glossary will be expanded as the project develops.