unsid

SID → faux-stereo WAV converter

Left  channel  →  MOS 6581  (warm, gritty, classic distortion)
Right channel  →  MOS 8580  (clean, precise, refined filters)

unsid renders the same Commodore 64 .sid file simultaneously through multiple independent emulation engines to create an organic stereo width or isolated per-voice stems.

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Features

• Stereo Mode: Renders the SID through a 6581 and 8580 simultaneously.
• Stems Mode: Parallel rendering of individual voices (3 per chip) as separate mono WAVs.
• Flexible Duration: Supports seconds or M:SS format (e.g., 6:12).
• Robust Detection: Automatically detects song duration via MD5, with fallback to filename lookup.

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Requirements

Requirement	Notes
libsidplayfp ≥ 2.0	apt install libsidplayfp-dev / brew install libsidplayfp
Rust ≥ 1.70
C++ toolchain	g++ or clang++ (needed by the sys crate's build script)

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Usage

unsid [OPTIONS] <INPUT>

Arguments:
  <INPUT>   Input .sid (or .mus) file

Options:
  -o, --output <PATH>       Output WAV file  [default: <input>.wav]
  -n, --tune <N>            Sub-tune number (0 = file default)  [default: 0]
  -r, --rate <HZ>           Sample rate in Hz                   [default: 44100]
  -d, --duration <DUR>      Max duration in seconds or M:SS     [default: 0]
      --stems               Render 6 individual voice stems (3x2)
      --chunk <SAMPLES>     Render chunk size                   [default: 4096]
      --filter-6581 <F>     6581 filter curve 0.0–1.0           [default: 0.5]
      --filter-8580 <F>     8580 filter curve 0.0–1.0           [default: 0.5]
  -h, --help
  -V, --version

Examples

# Convert to stereo — output is 'song.wav'
unsid song.sid

# Convert with duration as M:SS
unsid song.sid -o out.wav --duration 6:12

# Generate 6 parallel stem files (3 voices x 2 chips)
unsid song.sid --stems

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Song Length Detection

unsid automatically downloads the Songlengths.txt database if it is missing. Once present, it detects the duration of your SID files using the database:

1. MD5 Lookup: The tool calculates the MD5 hash of your .sid file and searches for a match in the database.
2. Filename Fallback: If the MD5 hash is not found, it attempts to match the file's name against the database entries.

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Listening tips

The 6581/8580 difference is most pronounced in:

• Filter-heavy tunes — the 6581 filter distorts warmly; the 8580 stays transparent.
• Digi-samples (4th-voice tricks) — the 6581 passes them clearly; the 8580 nearly mutes them without the "digiboost" mod.
• Combined waveforms — slightly thinner on 8580, adding airiness to the right channel.

Use a pair of headphones or a stereo-imager plugin to best appreciate the width.

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Crate dependency

unsid depends on sidplayfp-sys for the Rust FFI bindings to libsidplayfp, plus:

Crate	Purpose
clap 4	CLI argument parsing
hound 3	Pure-Rust WAV writer
anyhow 1	Ergonomic error handling

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License

MIT