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fix(audio): never feed chain processors blocks larger than prepared size (#85)
* fix(audio): never feed chain processors blocks larger than prepared size

WASAPI shared mode can deliver oversized blocks right after a device
start. The NAM core pre-allocates its conv ring/output buffers to the
Reset() maxBufferSize and only asserts (release no-op) on larger blocks;
one oversized block corrupts the conv ring state and garbles all
subsequent audio until the next Reset() — the 'first start heavily
distorted until tone reset / engine restart' bug.

- NAMProcessor::processBlock: process in slices of at most the prepared
  block size.
- SignalChain::process: slice oversized device blocks into prepared-size
  chunks before any slot (VST/NAM/IR) sees them.

See docs/audio-distortion-first-start-investigation.md.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* fix(audio): prefer same-backend duplex routing

* fix(audio): centre mono input; limit duplex to same-endpoint devices

Two issues found while testing the USB-guitar-cable path on Windows:

1. Centre a mono input. SourceChain::processBlock fell into the
   pass-through branch for a 1-channel input, filling only
   min(inputChannels, outputChannels) = 1 output channel and zeroing the
   rest, so a mono USB guitar cable played out of the left speaker only.
   A single-channel input is now broadcast across every output channel.

2. Only attempt the combined (duplex) device when input and output are
   the SAME physical endpoint. Two different endpoints of the same
   backend (USB cable in + separate speakers out) are independent
   hardware clocks; routing them through one duplex device was unstable
   across the app lifecycle (no audio until an explicit Apply, then
   distortion / dropouts / silent-in-song on navigation). Different
   endpoints now use the split path, whose ring bridges the two clocks.
   Same-endpoint duplex (one interface for in and out) keeps the
   low-latency win. Low latency for the two-device case is a follow-up
   that needs the device-lifecycle work (startup restore + reconfigure
   on navigation).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JEoFeTPSnz4NpwwCG52hnu

* fix(audio): probe same-endpoint duplex the same way apply routes it

Startup auto-apply (renderer init) fail-closes on probeDeviceOptionsDual's
`compatible` verdict, but the probe still measured a COMBINED duplex device
for any same-backend pair while setAudioDevices now opens split for
different endpoints. That mismatch made the startup probe describe a config
that isn't the one applied — surfacing as "no audio until I press Apply" for
a USB cable + separate speakers. Gate the probe's duplex path on the same
sameEndpointIntent (same type AND same device) the apply path uses, so a
two-device pair is probed via the split path it will actually run on.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01JEoFeTPSnz4NpwwCG52hnu

* fix(audio): close stale-format race when processors are added mid-reconfigure

addProcessor/replaceProcessor prepare the incoming processor off the
audio lock on N-API worker threads. A concurrent device reconfigure's
SignalChain::prepare() can't see that processor (not slotted yet), so a
slot could go live prepared at a stale sample rate / block size and stay
wrong until the next device restart — heard as pitch-shifted/garbled
monitoring when a chain loads while the device is being (re)opened
(widest window: WASAPI exclusive mode's slower open).

Re-check the chain's current format under the lock at insert/swap time
and re-prepare if it moved; log the transition to stderr so tester logs
show when the race fired. prepare() now publishes the format under the
lock so the check can't tear.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: ChrisBeWithYou <chris@rifflarr.local>
2026-07-08 22:44:26 +02:00
..
audio-distortion-first-start-investigation.md fix(audio): never feed chain processors blocks larger than prepared size (#85) 2026-07-08 22:44:26 +02:00
BUILD_ARCHITECTURE.md Clean release snapshot 2026-06-16 18:48:12 +02:00
CAPABILITY-MIGRATION.md fix(preload): expose desktop bridge as window.feedBackDesktop (#40) 2026-06-27 13:16:03 +02:00
SANDBOX-DESIGN.md Clean release snapshot 2026-06-16 18:48:12 +02:00
streamer-mix-outputs.md Streamer mix outputs (PR1): one stream bus → a 2nd output device (#49) 2026-06-29 00:49:25 +02:00
VST-SANDBOX-DIAG.md Clean release snapshot 2026-06-16 18:48:12 +02:00