Deep Voice: Real-time Neural Text-to-Speech
Table 1: Mean Opinion Scores (MOS) and 95% confidence intervals (CIs) for utterances. This MOS score is a relative MOS score obtained by showing raters the same utterance across all the model types (which encourages comparative rating and allows the raters to distinguish finer grained differences). Every batch of samples also includes the ground truth 48 kHz recording, which makes all our ratings comparative to natural human voices. 474 ratings were collected for every sample. Unless otherwise mentioned, models used phoneme durations and F0 extracted from the ground truth, rather than synthesized by the duration prediction and frequency prediction models, as well as a 16384 Hz audio sampling rate.
['[BOLD] Type', '[BOLD] Model Size', 'MOS±CI']
In order to separate the effect of the audio preprocessing, the WaveNet model quality, and the phoneme duration and fundamental frequency model quality, we present MOS scores for a variety of utterance types, including synthesis results where the WaveNet inputs (duration and F0) are extracted from ground truth audio rather than synthesized by other models. We purposefully include ground truth samples in every batch of samples that raters evaluate to highlight the delta from human speech and allow raters to distinguish finer grained differences between models; the downside of this approach is that the resulting MOS scores will be significantly lower than if raters are presented only with synthesized audio samples.