Allow to link against upstream espeak-ng

[leso-kn]

This PR allows to link piper-phonemize with the unmodified upstream version of espeak-ng.

Tested and working on glibc and musl.

[leso-kn]

Following up on a related discussion over here, this PR was changed to a more robust flow, the original implementation can be reviewed on this branch.

[synesthesiam]

Unless I'm missing something, this seems to not preserve punctuation (which is the reason for the espeak-ng fork). The problem is that espeak_TextToPhonemes does not return punctuation with phonemes. This is important for Piper, because voices use punctuation to correctly pause and for correct intonation.

The previous solution looked like it would do the right thing, despite being less robust.

[leso-kn]

Almost :) Both solutions do preserve punctionation, the difference is that the new solution does not outsource punctuation from espeak-ng, thus providing a hack-free solution at the cost of being marginally less flexible.

However, I did check the espeak-ng punctuation code and for the cases handled by piper-phonemize the chosen manual implementation should not be signifficantly less complete.

[synesthesiam]

My tests fail though when using this PR and espeak-ng 1.51. Have they changed things in a later release?

[leso-kn]

Sorry for the late reply, work came along!

Indeed, the new implementation was not handling the case where inputTextPointer was already NULL – that didn't happen during my tests because I tested through stdin, thus always had a \n behind my test phrases.

Should be fixed with c46ba6e, test.cpp is now passing on my side.

[synesthesiam]

Great, I'll check again. Thanks!

[leso-kn]

@synesthesiam FYI, PR was rebased on the latest master branch :)

[bzp83]

is this going to be merged?