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sndhplugin — Atari ST/STE SNDH

Plays .sndh (and content-gated .snd) using AtariAudio v1.01 by Arnaud Carré (Leonard/Oxygene), vendored verbatim under atariaudio/.

Why this exists

.sndh used to be decoded by sc68plugin, which drives libsc68 / emu68 / file68 / unice68 — GPL-3. GPL-3 cannot ship on the Mac App Store, so the mas variant had to lose the plugin. .sndh is 6,079 of the 7,976 rows sc68plugin owned (76%), so replacing just that one format keeps almost all of it.

AtariAudio is a natural fit rather than a lucky find: Arnaud Carré wrote the original StSound, which this project already ships as stsoundplugin, and AtariAudio is a from-scratch rewrite of that YM2149 work wrapped in a small ST machine. It is the engine behind his own SNDH-archive player.

What's in the box

component author licence
AtariAudio (SndhFile, AtariMachine, Ym2149c, Mk68901, SteDac) Arnaud Carré MIT
Musashi 68000 core (external/Musashi/) Karl Stenerud MIT
ICE! 2.4 depacker (external/ice_24.c) Hans Wessels public domain

No external dependencies, no float, no data files — an SNDH carries its own 68k driver, so unlike .sc68 there is no replay directory to ship. That is exactly why .sc68 could not follow it across (see below).

Dropped at vendor time: m68kmake.c (the opcode-table generator — m68kops.c is committed prebuilt upstream), m68kdasm.c and m68kfpu.c (unreachable in a 68000-only config).

Build notes

Three things in CMakeLists.txt are load-bearing, not cosmetic:

  • NDEBUG on the vendored sources. This project's Release build does not define it, and AtariAudio assert(false)s on input it dislikes — unsupported GEMDOS/XBIOS calls, unknown TRAP #n, illegal opcodes. Without NDEBUG one odd file in a 6,079-file corpus would abort() the app instead of skipping a song. Real load failures still come back through SndhFile::Load's return value, which is what fromFile keys on.
  • Hidden visibility + ld -r. aoplugin's Saturn core is also a Musashi and exports the same un-prefixed C entry points at global scope (nm -g libaoplugin.a shows _m68k_init, _m68k_execute, _m68k_read_memory_8 … all T). Partial-linking demotes our copy's to local symbols. Same treatment mikmodplugin needs.
  • priority() == 2. Above SC68Plugin's 1, which is above AdPlug's 0 on the shared .snd extension.

Relationship to sc68plugin

Both variants use AtariAudio for .sndh. In the plus build sc68plugin is still linked and still claims .sndh at lower priority, so anything AtariAudio declines falls through to libsc68 exactly as before — that build cannot regress. In the mas build sc68plugin is not compiled at all (CM_HAVE_SC68).

.sc68 does not move here and is not portable to AtariAudio as it stands: the container names an external replay routine, and those live in data/sc68/Replay/ as 95 prebuilt 68k binaries built from GPL-3 sc68 sources. There is no permissive equivalent and no published spec to clean-room. Those 1,894 rows stay plus-only and are dropped from the mas index by songHasNoPlayer() in MusicDatabase.cpp.

A phase 2 is conceivable — many .sc68 files embed their driver in an SCDA chunk rather than naming an external replay, and those could in principle run on the same Musashi. Nobody has measured what fraction that is.

Known limits

  • No seek within a subsong. The ST replay routine is driven tick by tick from its own init with no fast-forward, so seekTo accepts subsong changes (which restart the machine) and declines time seeks.
  • Single live instance. Musashi keeps CPU state in file-scope globals and AtariMachine.cpp routes its bus callbacks through one gCurrentMachine pointer. SNDHPlugin.cpp serialises construction and rendering on a static mutex; two concurrently rendering players would still trample each other. The host plays one tune at a time, and libsc68 had the same constraint.
  • Length only when tagged. AudioRender's loop counter is only meaningful when the file declares a length (TIME/FRMS). Untagged tunes report length 0 and are ended by the host's own song-length/silence logic, like any other plugin that reports 0.