Project 1: Raw ALSA Audio Player (Linux)

A command-line WAV player that talks directly to ALSA, bypassing PulseAudio/PipeWire entirely.

Quick Reference

Attribute Value
Primary Language See main guide
Alternative Languages N/A
Difficulty See main guide
Time Estimate See main guide
Knowledge Area See main guide
Tooling See main guide
Prerequisites C programming, basic Linux system calls, understanding of file descriptors

What You Will Build

A command-line WAV player that talks directly to ALSA, bypassing PulseAudio/PipeWire entirely.

Why It Matters

This project builds core skills that appear repeatedly in real-world systems and tooling.

Core Challenges

  • Opening and configuring PCM devices with snd_pcm_open() and hardware params
  • Understanding period size vs buffer size and why both matter
  • Handling blocking vs non-blocking I/O for real-time audio
  • Debugging underruns (xruns) when your code can’t feed samples fast enough

Key Concepts

  • Map the project to core concepts before you code.

Real-World Outcome

$ ./alsa_player music.wav

╔══════════════════════════════════════════════════════════════════╗
║                    ALSA Raw Audio Player v1.0                     ║
╠══════════════════════════════════════════════════════════════════╣
║ File: music.wav                                                   ║
║ Format: 16-bit signed little-endian, 44100 Hz, Stereo            ║
║ Duration: 3:42 (9,800,640 frames)                                ║
╠══════════════════════════════════════════════════════════════════╣
║ Device: hw:0,0 (HDA Intel PCH - ALC892 Analog)                   ║
║ Buffer size: 4096 frames (92.88 ms)                              ║
║ Period size: 1024 frames (23.22 ms)                              ║
╠══════════════════════════════════════════════════════════════════╣
║ Status: PLAYING                                                   ║
║ Position: 01:23 / 03:42                                          ║
║ Buffer fill: ████████████░░░░░░░░ 62%                            ║
║ XRUNs: 0                                                          ║
╚══════════════════════════════════════════════════════════════════╝

[Press 'q' to quit, SPACE to pause, '+/-' to adjust buffer size]

Implementation Guide

  1. Reproduce the simplest happy-path scenario.
  2. Build the smallest working version of the core feature.
  3. Add input validation and error handling.
  4. Add instrumentation/logging to confirm behavior.
  5. Refactor into clean modules with tests.

Milestones

  • Milestone 1: Minimal working program that runs end-to-end.
  • Milestone 2: Correct outputs for typical inputs.
  • Milestone 3: Robust handling of edge cases.
  • Milestone 4: Clean structure and documented usage.

Validation Checklist

  • Output matches the real-world outcome example
  • Handles invalid inputs safely
  • Provides clear errors and exit codes
  • Repeatable results across runs

References

  • Main guide: AUDIO_SOUND_DEVICES_OS_LEARNING_PROJECTS.md
  • Primary references are listed in the main guide