What does sox WARN wav: wave header missing extended part of fmt chunk mean?

Audacity 3 Help Forum Windows
1

After I edit existing WAV files in Audacity, I get them analyzed by:

The first line of the output is always:

sox WARN wav: wave header missing extended part of fmt chunk

What the heck does this mean? The files play in Audacity and other programs without issues. When I upload the original files not yet processed by Audacity into the online tool, this error is not reported.

2

From the WAVE/RIFF format specification:

An extended Format chunk is used for non-PCM data. The cbSize field gives the size of the extension.

  • For all formats other than PCM, the Format chunk must have an extended portion. The extension can be of zero length, but the size field (with value 0) must be present.

“Normal” WAV files, as produced by Audacity, contain PCM data, so there is no extended part of fmt chunk.