DSA is an open audio codec format designed for physical printed media and real-time motion-based playback.
Part of the Digilog open physical audio format.
This repository contains the normative format specification and research documentation for DSA. It is licensed under CC BY-SA 4.0 — you are free to implement, adapt, and build on this specification as long as you credit the source and share derivatives under the same license.
| File | Contents |
|---|---|
SPEC.md |
Normative implementor specification — MUST/SHOULD requirements, bitstream layout, all constants |
RESEARCH.md |
Scientific documentation — theory, design decisions, benchmarks, future directions |
The reference implementation of DSA is maintained separately under GPL v3:
It includes:
- MDCT frame analyzer, perceptual quantizer, K/B-frame encoders
- Huffman entropy coder, layered bitstream packer
- Decoder with reverse playback, variable speed, and analog degradation
- Digilog disc encoder interface
- Unified CLI, benchmark suite, test suite (74 tests)
DSA is an audio codec built for a specific purpose: encoding audio into a physical printed medium playable by scanning with a camera — including in real time while the medium is in motion (spinning on a turntable, scratched by a DJ, hand-scanned across a surface).
| Property | MP3 / AAC / Opus | DSA |
|---|---|---|
| Designed for physical media | No | Yes |
| Layered scalable decoding | No | Yes |
| Native reverse playback | No | Yes |
| Motion-aware (variable speed) | No | Yes |
| Graceful analog degradation | No | Yes |
| Maps to physical disc rings | No | Yes |
- Transform: MDCT, N=2048, M=1024, sine window, 238 dB TDAC SNR
- Frame structure: GOP=8, K-frames (self-contained) + B-frames (bidirectional)
- Layers: L0 (8 bands, 20–800 Hz), L1 (16 bands, 800–6 kHz), L2 (24 bands, 6–22 kHz)
- Entropy coding: Huffman, static codebooks per layer (L0/L1/L2, Laplacian-derived)
- Bitstream: DSA1 format, CRC32, two encoding modes (discrete / gradient)
This specification is licensed under Creative Commons Attribution-ShareAlike 4.0 International.
See LICENSE or https://creativecommons.org/licenses/by-sa/4.0/
Implementing this specification does not require you to adopt GPL v3. The specification itself is CC BY-SA 4.0 — you may write a proprietary implementation as long as you credit this specification and share any modifications to the spec itself under CC BY-SA 4.0.
The reference implementation is licensed separately under GPL v3 at pisdronio/dsa. This is the same boundary used by open standards such as Opus (RFC 6716, IETF) and MPEG-4 SVC (ISO/IEC 14496), where the specification and implementation carry independent licenses.
- digilog-spec — the Digilog physical format specification
- dsa — DSA reference implementation (GPL v3)
Scan the groove.