FFmpeg audio contains NaN or Inf: trace effects and decoding upstream

Symptoms and scope

A codec rejecting nonfinite samples is not necessarily missing. Follow the audio entering it back through processing and decoding.

Error fragments for search; IDs, values and filenames may vary:

Input contains (near) NaN/+-Inf
Audio encoding failed

Source-supported context

A VideoHelperSuite report records the AAC encoder message after a user inserted reverb before VideoCombine. A maintainer asked whether core SaveAudio nodes work, to locate whether the problem precedes VideoHelperSuite. The issue remains open and does not establish that reverb itself, every audio effect or FFmpeg installation is the root cause. The project README identifies the extension involved.

Cases to distinguish

1. An effect, gain or mixing stage generates invalid values detected only during encoding.

2. An earlier decoder or precision conversion has a numerical problem without a separate visible failure.

3. Input media or an extension's sample-data conventions do not match expectations.

Diagnostic sequence

The sequence below is an editorial procedure based on the cited context, not a diagnosis already confirmed for your environment.

Step 1. Preserve stderr and confirm that it explicitly reports NaN/Inf rather than a missing path or encoder.

Step 2. In a recoverable copy, use a core SaveAudio node on the input and again after the suspect effect, if that output can be connected. Compare whether the audio can be saved and played before VideoCombine; keep the original file private and unchanged. This locates the failing stage but does not alone identify the numerical cause.

Step 3. Bypass effects and send the original audio to VideoCombine with the same video frames. Restore reverb, gain, mixing and conversions one at a time to find the first minimal failing branch. Compare the same short clip and output settings.

Step 4. Record that branch's version/settings and seek an upstream fix. Do not silently zero every nonfinite value without understanding the audio consequences.

Completion check

Stages process valid audio and encoding completes with sensible content, level and duration. Absence of an exception alone does not validate the effect.

Limitations and cautions

Silence and nonfinite samples are different failures. No real user audio or numerical audit of the effect implementation is included.

Original sources

• VHS FFmpeg audio contains NaN/Inf — checked 2026-09-26.
• VideoHelperSuite README — checked 2026-09-26.

Source review and separate English editorial pass: 2026-09-26. No local audio processing, encoding or GPU run occurred; no runtime repair is claimed.

Related troubleshooting and guides

• VHS output is nearly silent: inspect audio dtype before increasing gain
• Video export fails or plays incorrectly: check frames, encoding and audio separately