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Fix reverse-read timing and add small-buffer safeguard in AccidentalReverse mode #82

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Fix reverse-read timing and add small-buffer safeguard in AccidentalReverse mode #82

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28 changes: 22 additions & 6 deletions core/src/orbit_delay_core.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -713,19 +713,35 @@ float OrbitDelayCore::processChannelFast(float input,
const float maxGuardBySize = 0.25f * delaySize;
const float guardSamples = clampf(kOrbitReadGuardMinSamples, 1.0f, maxGuardBySize);
if (readMode_ == ReadMode::AccidentalReverse) {
float reverseDelaySamples = params.tempoDelaySamples + spread + lfoSamples;
// Effective reverse delay follows the smoothed tempo delay plus the same
// channel-dependent offsets used by the forward path.
float reverseDelaySamples = params.tempoDelaySamples + params.offsetSamples + spread + lfoSamples;
reverseDelaySamples = clampf(reverseDelaySamples, guardSamples, fmaxf(delaySize - guardSamples, guardSamples));
float& reverseCounter = (&delay == &delayL_) ? reverseCounterL_ : reverseCounterR_;
float& reverseWindowSize = (&delay == &delayL_) ? reverseWindowSizeL_ : reverseWindowSizeR_;
const float readPos = wrapPosFloat(writePos - reverseDelaySamples + reverseCounter, delaySize, invDelaySize);
const float distanceBackward = wrapPosFloat(writePos - readPos, delaySize, invDelaySize);
if (distanceBackward < guardSamples || distanceBackward > (delaySize - guardSamples)) {

// Safe fallback: insufficient usable region between the two guard bands
// for the minimum reverse window size.
constexpr float kMinReverseWindowSamples = 8.0f;
if (delaySize < kMinReverseWindowSamples + 2.0f * guardSamples) {
reverseCounter = 0.0f;
reverseWindowSize = 0.0f;
reverseDelaySamples = guardSamples;
wet = 0.0f;
baseReadPos = wrapPosFloat(writePos - guardSamples, delaySize, invDelaySize);
Comment on lines 727 to +731

@gemini-code-assist gemini-code-assist Bot May 27, 2026

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medium

The assignment reverseDelaySamples = guardSamples; is a dead store because reverseDelaySamples is a local variable that is not used anywhere else in this fallback branch. Removing it simplifies the code.

Suggested change
reverseCounter = 0.0f;
reverseWindowSize = 0.0f;
reverseDelaySamples = guardSamples;
wet = 0.0f;
baseReadPos = wrapPosFloat(writePos - guardSamples, delaySize, invDelaySize);
reverseCounter = 0.0f;
reverseWindowSize = 0.0f;
wet = 0.0f;
baseReadPos = wrapPosFloat(writePos - guardSamples, delaySize, invDelaySize);

} else {
const float readPos = wrapPosFloat(writePos - reverseDelaySamples + reverseCounter, delaySize, invDelaySize);
const float distanceBackward = wrapPosFloat(writePos - readPos, delaySize, invDelaySize);
if (distanceBackward < guardSamples || distanceBackward > (delaySize - guardSamples)) {
reverseCounter = 0.0f;
reverseWindowSize = 0.0f;
reverseDelaySamples = guardSamples;
}
// Window size is explicitly derived in readReverseWindowed() from this
// effective smoothed delay value.
wet = readReverseWindowed(delay, reverseDelaySamples, writePos, delaySize, invDelaySize, reverseCounter, reverseWindowSize);
baseReadPos = wrapPosFloat(writePos - reverseDelaySamples + reverseCounter, delaySize, invDelaySize);
Comment on lines +742 to +743

@gemini-code-assist gemini-code-assist Bot May 27, 2026

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high

In the reverse-read path, baseReadPos is calculated using reverseCounter after it has been incremented inside readReverseWindowed(). This causes a 1-sample mismatch between the actual read position used for the wet signal and the base read position used for the feedback tap mixer. Calculating baseReadPos before calling readReverseWindowed() ensures they are perfectly aligned.

Suggested change
wet = readReverseWindowed(delay, reverseDelaySamples, writePos, delaySize, invDelaySize, reverseCounter, reverseWindowSize);
baseReadPos = wrapPosFloat(writePos - reverseDelaySamples + reverseCounter, delaySize, invDelaySize);
baseReadPos = wrapPosFloat(writePos - reverseDelaySamples + reverseCounter, delaySize, invDelaySize);
wet = readReverseWindowed(delay, reverseDelaySamples, writePos, delaySize, invDelaySize, reverseCounter, reverseWindowSize);

}
wet = readReverseWindowed(delay, reverseDelaySamples, writePos, delaySize, invDelaySize, reverseCounter, reverseWindowSize);
baseReadPos = wrapPosFloat(writePos - reverseDelaySamples + reverseCounter, delaySize, invDelaySize);
} else {
const float orbitDelaySamples = params.tempoDelaySamples * params.orbit;
const float modulatedDelaySamples = orbitDelaySamples + params.offsetSamples + spread + lfoSamples;
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