Case study

Microsoft Anna: a bit-exact C rebuild of the TTS20 engine

Rebuilds Microsoft Anna, the Windows Vista and Windows 7 TTS20 voice, as C99 that reads the original voice data files. The README reports bit-exact PCM against the real engine on its test lines.

Targets: Binary
Category: Independent reconstruction cases
Relationship: Independent reconstruction project
Sources reviewed: 2026-11-09

Stars: 6
Last commit: 2026-09-20
Language: C

GitHub data as of 2026-11-09

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Requirements & limits

Prerequisites: Needs a C99 compiler and your own Anna data from a Windows Vista or 7 install, or from the Windows 7 voices installer. The README says no Microsoft code or data is in the repository. It says not to use -ffast-math and to keep -ffp-contract=off.
Scope: This is the SAPI 5 TTS20 engine the README calls Mulan internally. tools/anna_extract.py is the command the README gives for turning an install or the voices installer into the data folder.
Testing evidence: The README's end-to-end row says 579/579 test lines are bit-exact, including the SAPI XML tags it lists, and identical with MSVC x86/x64, clang, and GCC. Its WMA Voice 9 row says all 66218 blocks plus 25000 random reads match Windows' 32-bit WMSPDMOD.DLL.
License: LICENSE is the MIT License, copyright 2026 KamiKitsune420. The voice data remains Microsoft's and is not included.

Cite

BibTeX

@misc{ms-anna-tts-case,
  title = {{Microsoft Anna: a bit-exact C rebuild of the TTS20 engine}},
  howpublished = {\url{https://github.com/KamiKitsune420/ms-ana-decomp}},
  url = {https://github.com/KamiKitsune420/ms-ana-decomp},
  urldate = {2026-11-09},
  note = {Awesome REA entry: \url{https://awesomerea.org/resources/ms-anna-tts-case/}}
}

Plain text

Microsoft Anna: a bit-exact C rebuild of the TTS20 engine. https://github.com/KamiKitsune420/ms-ana-decomp (accessed 2026-11-09). Awesome REA entry: https://awesomerea.org/resources/ms-anna-tts-case/

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Primary sources

README.md GitHub · KamiKitsune420/ms-ana-decomp · Revision a8da046
LICENSE GitHub · KamiKitsune420/ms-ana-decomp · Revision a8da046