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* audio: flush denormals in the RT path + normalize the backing track
Two realtime-audio fixes (engine only — no change to amp/effect DSP):
1. Denormal flush (FTZ/DAZ). The signal path is full of IIR state (NAM, cab
IRs, VST amp/EQ/comp chains); after each note that state decays toward zero
and lands in the denormal range, where each float op is 10-100x slower. That
produced sporadic CPU spikes -> buffer underruns heard as random "scratches"
plus frame stutter (worse with larger buffers, independent of song/tone).
Add a scoped juce::ScopedNoDenormals at the three RT entry points:
- AudioEngine::audioDeviceIOCallbackWithContext (whole callback)
- SignalChain::process (the plugin chain)
- the sandbox worker's plugin processBlock in src/vst-host/main.cpp
(VST3s run OUT-OF-PROCESS, so the host-side FTZ doesn't reach them)
Denormals are sub -300 dBFS, so this is inaudible — CPU only, no tone change.
2. Backing-track loudness normalizer (BackingLeveler.h). Brings each song's
backing to a consistent -12 LUFS so songs don't jump in level, applied in
renderBackingBlockLocked BEFORE the mixer's backing-volume fader (so the
fader still attenuates). Short-term BS.1770 K-weighted AGC (slow, no pumping)
+ a -1 dBFS brickwall limiter. RT-safe (no allocation in process()).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
* audio: extend denormal flush to the split-output path + reuse chain MidiBuffer
Opt-1 low-risk RT tidy-ups (no DSP/tone change):
- ScopedNoDenormals in audioOutputCallback (the split-mode output clock that
renders the backing track + phase-vocoder + leveler) — the primary callback's
scope doesn't reach this separate output thread, leaving an IIR/decay path
unprotected (a remaining source of the periodic "scratches").
- SignalChain::process reuses one juce::MidiBuffer across slots instead of
copy-constructing it per slot per block (avoids RT-thread allocation).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
* audio: per-slot pan + parallel branch routing (St-1 stereo, engine side)
Adds pan-only stereo to the signal chain so the node editor can place one amp
left and another right, pan effects, and let stereo plugins pass true L/R.
ProcessorSlot gains two fields:
- pan : -1..+1 constant-power, applied to that slot's output (0 = no-op)
- branch : 0 = trunk (serial), >=1 = a parallel branch id
SignalChain::process keeps a bit-identical serial fast path when no slot has a
branch. When branches exist it runs the trunk-pre slots in place, snapshots that
as the split source, processes each branch on its own pre-allocated scratch
buffer, pans it, sums the branches into a merge bus, then runs any trunk-post
slots on the merged signal. Scratch is sized in prepare() (never on the RT
thread); falls back to serial for a non-stereo / oversized block.
The dual-mono amp output + post-amp pan is what yields "amp A left, amp B right"
without touching NAM or amp DSP. Preset schema emits pan/branch only when
non-default (mono presets unchanged); N-API gains setPan/setBranch and
getChainState/loadPreset round-trip them.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
* audio: per-branch source channel (St-2) — feed a split L/R into separate branches
Extends the parallel-branch model so a stereo-out gear (e.g. a stereo delay) can
send its L output to one branch and its R to another. ProcessorSlot gains
branchSrc (0 = both, 1 = L, 2 = R); when seeding a branch from the split source,
L-only / R-only mono-izes that channel into the branch. Read from any slot in the
branch. N-API setBranchSrc + getChainState/preset round-trip it. Default 0 keeps
existing routing identical.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
* audio-bridge: expose setPan/setBranch/setBranchSrc to the renderer
The engine N-API gained the stereo routing setters (setPan/setBranch/
setBranchSrc) but the main-process IPC handlers + the preload bridge didn't
forward them, so window.slopsmithDesktop.audio.setPan was undefined and the
node editor's stereo controls no-op'd. Wire all three through audio:setPan /
setBranch / setBranchSrc.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
* audio: run scanned VSTs in-process + forward params + cut RT stalls
Big CPU/latency win for chains with VST plugins, plus the missing parameter
path. The out-of-process sandbox exists to crash-isolate the SCAN of unknown
plugins; a plugin only reaches a chain after it scanned cleanly, so paying the
per-block IPC cost (N serial round-trips, memcpy, poll waits) for every block
of playback was pure overhead.
- shouldSandbox(): default VST3 playback to IN-PROCESS. The runtime crash
blocklist + launch sentinel still route a faulting plugin back through the
sandbox on its next load, so it self-heals; only genuinely crash-prone gear
keeps paying for isolation. Eliminates the IPC round-trips + the per-load
subprocess spawn that caused the load-time "scratches".
- SignalChain::clear(): detach slots under a brief lock, destroy them OFF the
lock. Sandbox teardown is slow; doing it under `lock` starved the RT
ScopedTryLock and dropped audio blocks on every chain reload.
- AudioChannel::popBlock(): bounded busy-spin on the write index before the
blocking poll() — a fast plugin's output lands within microseconds, so we
skip the syscall + doorbell wakeup latency; a slow plugin falls through to the
efficient wait (correctness + heavy-chain cost unchanged).
- SandboxedProcessor::setSandboxedParameter() + SignalChain::setParameter()
route param changes to a sandboxed plugin over the control pipe (kSetParameter)
— the JUCE getParameters() proxy layer isn't wired, so without this a
sandboxed plugin's knobs/preset never reached it and it played at defaults.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
* audio: PR #24 review follow-ups — POSIX fault guard + routing/spin/leveler fixes
Follow-up fixes from review of PR #24.
== POSIX in-process plugin fault guard (the main one) ==
PR #24 makes scanned VSTs run in-process by default. invokePlugin()'s catch(...)
only catches a plugin fault on Windows (where /EHa maps the SEH access violation
to a C++ exception); on macOS/Linux a plugin SIGSEGV during playback took down
the whole app, breaking the fail-soft-audio + cross-platform guarantees.
Add a POSIX fault guard in SignalChain.cpp: install chained SIGSEGV/SIGBUS/
SIGFPE/SIGILL handlers; while a guarded plugin call is live on the current
thread (thread-local, initial-exec TLS so the handler stays async-signal-safe),
siglongjmp() back into invokePlugin() and take the SAME blocklist+leak+survive
path as Windows. Faults outside a guarded call chain to the previously-installed
handler (V8/ASan/default), so real crashes and sanitizers are never masked. The
guard's armed flag is restored on EVERY exit from the guarded region — normal
return, signal-fault longjmp, and a normal C++ exception from the plugin — so a
thread is never left armed with a stale landing pad. Known limit: stack-overflow
faults aren't reliably caught (no sigaltstack on JUCE audio threads).
Comments in SandboxFactory_shared.cpp updated to match the kept in-process
default (the stale 'every VST3 sandboxes' / 'diagnostic tagging only' notes).
== Smaller correctness/quality fixes ==
- SignalChain parallel path: a branch==0 (trunk) slot interleaved inside the
branch region was run by none of the loops -> silently dropped. Detect the
region first and fall back to a serial chain (jassertfalse in debug) so no
slot is lost if the node-editor contiguity invariant breaks.
- AudioChannel pop busy-spin: add a cpuRelax() (_mm_pause / arm yield) hint.
- BackingLeveler: reset AGC/limiter state on loadBackingTrack so a new song
doesn't inherit the previous track's gain follower and briefly mis-level.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
* test: integration test for the in-process plugin fault guard
Drives deliberately-faulting in-process AudioProcessors through a real
SignalChain::process() and asserts the host survives, the processor is released,
and it's added to the crash blocklist (shouldSandbox() then routes it
out-of-process). Covers BOTH fault kinds: a hardware SIGSEGV (POSIX guard /
Windows SEH) and a normal C++ exception (the path that must leave the guard
disarmed). End-to-end counterpart to the standalone mechanism check — exercises
the actual invokePlugin() guard.
Lives in the POSIX-only sandbox e2e harness (already links juce_audio_processors
+ the full sandbox set). Leak detection is disabled for the target because the
guard leaks the faulting processor by design.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---------
Co-authored-by: Jafz2001 <ignacio.fritis@mundotelecomunicaciones.cl>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Co-authored-by: Byron Gamatos <xasiklas@gmail.com>
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|---|---|---|
| .claude/skills | ||
| .devcontainer | ||
| .github/workflows | ||
| .packages | ||
| .specify | ||
| cmake | ||
| docs | ||
| JUCE@9971c75b2c | ||
| resources | ||
| scripts | ||
| src | ||
| tests | ||
| .build-config.json | ||
| .gitignore | ||
| .gitmodules | ||
| CMakeLists.txt | ||
| CONTRIBUTORS.md | ||
| LICENSE | ||
| package.json | ||
| README.md | ||
| THIRD_PARTY_LICENSES.md | ||
| tsconfig.json | ||
| WINDOWS_BUILD_REQUIREMENTS.md | ||
Slopsmith Desktop
Standalone cross-platform desktop app that wraps Slopsmith with integrated VST hosting, amp modeling, audio I/O, and full plugin support.
Install
Prebuilt installers for the latest tagged release are published on the GitHub Releases page.
| Platform | Download | Notes |
|---|---|---|
| Windows 10/11 (x64) | Slopsmith.Setup.<version>.exe |
NSIS installer. On first run Windows SmartScreen may warn — click More info → Run anyway. |
| macOS 12+ (Apple Silicon) | Slopsmith-<version>-arm64.dmg |
Signed & notarized. Intel Macs are not currently published — build from source. |
| Linux (x86_64) | Slopsmith-<version>.AppImage |
chmod +x then run. Portable, no install step. |
| Debian / Ubuntu (x86_64) | slopsmith-desktop_<version>_amd64.deb |
sudo apt install ./slopsmith-desktop_<version>_amd64.deb |
First launch may take a minute or two while ML model caches populate in the app cache directory. Subsequent launches are fast.
There is currently no Homebrew, winget, Chocolatey, Scoop, Flatpak, or Snap distribution — download directly from Releases. The app does not yet ship an auto-updater; check Releases periodically for new versions.