feat: add setStereoSeparation method to ChiptuneJsPlayer#4
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Add a main-thread entry point to update the stereo-separation render
param on a running module, and to update the worklet's persisted
this.config.stereoSeparation so subsequently-loaded modules inherit
the value without a reload.
Today the worklet's play() handler already reads
this.config.stereoSeparation and stamps it via
openmpt_module_set_render_param at module-create time, but consumers
have no way to mutate the config from the main thread after the
ChiptuneJsPlayer constructor's auto-config post. setStereoSeparation
fills that gap by posting a {cmd:'setStereoSeparation', val} message
that the worklet handles by mutating this.config and (when a module
is loaded) calling set_render_param immediately.
The worklet-side handler clamps incoming values to [0, 200] (the
libopenmpt documented range; 100 = default, 0 = mono) and falls back
to the default 100 on non-finite values, so callers can be liberal
in what they send.
Use case: an Amiga MOD player UI that exposes a "stereo separation"
slider letting listeners gradually collapse the classic hard-panned
field toward mono. Without this method the only way to change the
value after page load is to recreate the ChiptuneJsPlayer (destroys
the AudioContext + reloads the worklet, ~0.5s silence on every
slider tick).
The .min.js siblings are not regenerated in this PR -- I assume
minify.js runs as part of a release cut. Happy to add them if
preferred.
Assisted-by: ClaudeCode:claude-opus-4-7
Signed-off-by: Ronny Trommer <ronny@no42.org>
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Add a Stereo separation slider (0% mono → 100% libopenmpt default) to
the Sound pane. Persists under audio.stereoSeparation and rides the
ChiptuneJsPlayer constructor config so the worklet receives it via
the auto-posted {cmd:'config'} message — no per-track re-apply, no
race against audioWorklet.addModule().
Local vendored chiptune3 patch adds a typed setStereoSeparation
method; upstream PR DrSnuggles/chiptune#4 mirrors it.
Assisted-by: ClaudeCode:claude-opus-4-7
indigo423
added a commit
to no42-org/CoolModFiles
that referenced
this pull request
May 12, 2026
Add a Stereo separation slider (0% mono → 100% libopenmpt default) to
the Sound pane. Persists under audio.stereoSeparation and rides the
ChiptuneJsPlayer constructor config so the worklet receives it via
the auto-posted {cmd:'config'} message — no per-track re-apply, no
race against audioWorklet.addModule().
Local vendored chiptune3 patch adds a typed setStereoSeparation
method; upstream PR DrSnuggles/chiptune#4 mirrors it.
Assisted-by: ClaudeCode:claude-opus-4-7
Signed-off-by: Ronny Trommer <ronny@no42.org>
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Summary
Adds a
setStereoSeparation(val)method toChiptuneJsPlayerand a matching'setStereoSeparation'case in the worklet'shandleMessage_. Mirrors the existingsetPitch/setTemposhape.Why
The worklet's
play()already readsthis.config.stereoSeparationand stamps it viaopenmpt_module_set_render_paramat module-create time, anddefaultCfg.stereoSeparationis a public config key, but there's currently no path from the main thread to mutate the value after the constructor's auto-config post. Today, changing stereo separation after page load means recreating theChiptuneJsPlayer— destroying theAudioContext, reloading the worklet, and giving the listener ~0.5s of silence on every tick of a UI slider.This method fills the gap symmetrically with the existing render-param consumer in
play():{cmd:'setStereoSeparation', val}from the main thread.this.config.stereoSeparationso subsequently-loaded modules inherit the value._openmpt_module_set_render_param(modulePtr, OPENMPT_MODULE_RENDER_STEREOSEPARATION_PERCENT, val)for an immediate audible update.The worklet clamps incoming values to
[0, 200](libopenmpt's documented range —100= default,0= mono,200= exaggerated) and falls back to100on non-finite values, so callers can be liberal in what they send.Use case
The CoolModFiles project is using this library and wants a "stereo separation" slider in the player UI so headphone listeners can gradually collapse the classic hard-panned MOD field toward mono. The slider lives in a settings panel and updates the value live as the user drags. A live demo is on https://mods.amiga.fans.
Diff
+14 lines, 2 files. No new dependencies, no API removals.chiptune3.js:setStereoSeparation(val) { this.postMsg('setStereoSeparation', val) }placed next tosetTempo.chiptune3.worklet.js: newcase 'setStereoSeparation'inhandleMessage_placed next tosetTempo.Notes
.min.jssiblings are not regenerated in this PR — I assumedminify.jsruns as part of a release cut. Happy to include them if you'd prefer.v3(current default).Thanks for
chiptune— it's the audio backbone of the site. Glad to send fixes back when we have them.