eval.py: Evaluation broken about tacotron HOT 3 OPEN

Technically speaking mel-scale is not exactly the same as log. See https://en.wikipedia.org/wiki/Mel_scale. The paper says they use melspectrogram and linear-scale log magnitude (spectrogram). So the spectrogram2wav converts the predicted magnitude to the waveform. It has nothing to do with melspectrogram.

The reason why people care about whether we appy logarithm to magnitude in training is two, in my opinion. First, we or at least I don't have a full understanding of why it is useful. Second, in practice it needs our attention in that there are three times of padding--reducing frames, dynamic padding, and convolution with same padding.

For now I don't know why there's a problem when you set use_log_magnitude to False. I'll check soon.

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Oh now I know the reason. For the plain magnitude we must not allow negative numbers because of the power. I simply clipped the value to zero. https://github.com/Kyubyong/tacotron/blob/master/eval.py#L70

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Well, you're right when you say that mel isn't exactly log. And to be honest, my explanation isn't much more then a first guess. I didn't check every part of the code and I agree with you: I'm not quite sure what the log stuff is all about.

But: Even after your latest commits, I can't generate non-silent audio from my model if use_log_magnitude is False

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