The Kokoro decoder's generator computes the phase of its forward STFT
with atan2(imag, real), which the exported graph implements as an
unguarded imag / real followed by Atan. imag and real are produced by
two Conv nodes. quantize_dynamic also quantized these two convs; at DC
and Nyquist the quantized imag is exactly 0, and with int8 arithmetic
real can become exactly 0 there as well, giving 0 / 0 = NaN.
On macOS arm64 the NaN spreads over the whole output, so short pieces of
text come back as all-NaN audio. On x64 the following
DynamicQuantizeLinear happens to drop the NaN, which hides the problem
but does not remove it.
Pass the two convs as nodes_to_exclude, for v1.0 and v1.1-zh. v0.19
computes the STFT without Conv nodes and is not affected.
The released int8 models kokoro-int8-multi-lang-v1_0 and
kokoro-int8-multi-lang-v1_1 need to be regenerated with this change.
Fixes#4086
Stef