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Guard ScaleSilence against invalid silence scales #3745

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Merged
csukuangfj merged 1 commit into from
Jul 10, 2026
Merged

Guard ScaleSilence against invalid silence scales #3745

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11 changes: 11 additions & 0 deletions sherpa-onnx/csrc/offline-tts.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -35,6 +35,17 @@ GeneratedAudio GeneratedAudio::ScaleSilence(float scale) const {
if (scale == 1) {
return *this;
}

// scale is used to shorten long pauses, so it is normally within (0, 1).
// Values outside this range are rejected: n below is computed as
// interval_length * scale and converted to an int32_t, and NaN, infinity or
// a very large scale make that conversion undefined. Note that any
// comparison with NaN is false, so NaN is rejected here as well.
if (!(scale >= 0.01f && scale <= 2.0f)) {
SHERPA_ONNX_LOGE("Silence scale %f is not in [0.01, 2]. Skip scaling.",
scale);
return *this;
}
Comment on lines +44 to +48

@coderabbitai coderabbitai Bot Jul 10, 2026

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🗄️ Data Integrity & Integration | 🟠 Major | ⚡ Quick win

Config validation range [0.001, ∞) doesn't match ScaleSilence range [0.01, 2.0].

OfflineTtsConfig::Validate() at line 224 only rejects silence_scale < 0.001 with no upper bound, but ScaleSilence rejects values outside [0.01, 2.0]. Values in [0.001, 0.01) or above 2.0 pass config validation but are silently no-op'd at runtime — the user gets unscaled audio with no indication beyond a log message.

Align the two ranges to avoid surprising behavior:

🔧 Proposed fix for Validate() 
-  if (silence_scale < 0.001) {
-    SHERPA_ONNX_LOGE("--tts-silence-scale '%.3f' is too small", silence_scale);
+  if (silence_scale < 0.01f || silence_scale > 2.0f) {
+    SHERPA_ONNX_LOGE("--tts-silence-scale '%.3f' is not in [0.01, 2]",
+                     silence_scale);
     return false;
   }

Also applies to: 224-227

🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@sherpa-onnx/csrc/offline-tts.cc` around lines 44 - 48, Align
OfflineTtsConfig::Validate() with ScaleSilence by validating silence_scale
within the inclusive range [0.01, 2.0], rejecting values below 0.01 or above 2.0
and reporting the validation error consistently. Update the existing
silence_scale validation logic in OfflineTtsConfig::Validate() so all values
accepted by configuration are handled by ScaleSilence without being silently
skipped.

🎯 Functional Correctness | 🟠 Major | ⚡ Quick win

Range check rejects scale = 0, breaking existing pause-removal behavior.

The PR summary states "Scale 0 retains its existing behavior of removing pauses," but 0 < 0.01f fails the range check, so ScaleSilence(0) now logs an error and returns unscaled audio with pauses intact. Previously, scale = 0 produced n = 0, effectively removing all silence intervals.

If scale = 0 should still remove pauses, lower the bound to 0.0f:

🔧 Proposed fix 
-  if (!(scale >= 0.01f && scale <= 2.0f)) {
-    SHERPA_ONNX_LOGE("Silence scale %f is not in [0.01, 2]. Skip scaling.",
+  if (!(scale >= 0.0f && scale <= 2.0f)) {
+    SHERPA_ONNX_LOGE("Silence scale %f is not in [0, 2]. Skip scaling.",
                      scale);

If rejecting scale = 0 is intentional, the PR summary should be corrected to reflect this behavior change.

📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
if (!(scale >= 0.01f && scale <= 2.0f)) {
SHERPA_ONNX_LOGE("Silence scale %f is not in [0.01, 2]. Skip scaling.",
scale);
return *this;
}
if (!(scale >= 0.0f && scale <= 2.0f)) {
SHERPA_ONNX_LOGE("Silence scale %f is not in [0, 2]. Skip scaling.",
scale);
return *this;
}
🤖 Prompt for AI Agents 
Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

In `@sherpa-onnx/csrc/offline-tts.cc` around lines 44 - 48, Update the range
validation in ScaleSilence to allow scale = 0 by changing the lower bound from
0.01f to 0.0f, preserving the existing behavior that removes silence intervals
when scaling by zero.

// if the interval is larger than 0.2 second, then we assume it is a pause
int32_t threshold = static_cast<int32_t>(sample_rate * 0.2);

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