HIGH FIDELITY SPEECH SYNTHESIS WITH ADVERSARIAL NETWORKS

1 . A method of training a feedforward generative neural network having a plurality of generative parameters and configured to generate output audio examples using conditioning text inputs,

wherein each conditioning text input comprises a respective linguistic feature representation at each of a plurality of input time steps,

wherein the feedforward generative neural network is configured to receive a generative input comprising a conditioning text input and to process the generative input to generate an audio output that comprises respective audio samples at each of a plurality of output time steps, and

wherein the training comprises:

obtaining a training conditioning text input;

processing a training generative input comprising the training conditioning text input using the feedforward generative neural network in accordance with current values of the generative parameters to generate a training audio output;

processing the training audio output using each of a plurality of discriminators, wherein:

the plurality of discriminators comprises one or more conditional discriminators, wherein each conditional discriminator processes a respective subset of the training audio output and the training conditioning text input to generate a prediction of whether the training audio output is a real audio example or a synthetic audio example, and

the plurality of discriminators comprises one or more unconditional discriminators, wherein each unconditional discriminator processes a respective subset of the training audio output but not the training conditioning text input to generate a prediction of whether the training audio output is a real audio example or a synthetic audio example;

determining a first combined prediction by combining the respective predictions of the plurality of discriminators; and

determining an update to the current values of the generative parameters to increase a first error in the first combined prediction.

2 . The method of claim 1 , wherein:

each discriminator has a plurality of respective discriminative parameters,

each conditional discriminator processes the training audio output and the training conditioning text input in accordance with current values of the respective discriminative parameters,

each unconditional discriminator processes the training audio output but not the training conditioning text input in accordance with current values of the respective discriminative parameters, and

the method further comprises determining an update to the current values of the discriminative parameters to decrease the first error in the first combined prediction.

3 . The method of claim 1 , wherein the training further comprises:

obtaining a real audio example and a real conditioning text input comprising a transcript of the real audio example;

processing i) the real audio example and the real conditioning text input using each of the conditional discriminators and ii) the real audio example but not the real conditioning text input using each of the unconditional discriminators, wherein each discriminator generates a prediction of whether the real audio example is a real audio example or a synthetic audio example;

determining a second combined prediction by combining the respective predictions of the plurality of discriminators; and

determining an update to the current values of the discriminative parameters to decrease a second error in the second combined prediction.

4 . The method of claim 1 , wherein the feedforward generative neural network comprises a sequence of groups of convolutional neural network layers, wherein each group includes one or more dilated convolutional layers.

5 . The method of claim 1 , wherein each discriminator comprises a discriminator neural network that comprises a sequence of groups of convolutional neural network layers, wherein each group includes one or more dilated convolutional layers.

6 . The method of claim 1 , wherein the feedforward generative neural network comprises a sequence of groups of convolutional neural network layers, wherein one or more groups include one or more respective upsampling layers to account for a first ratio between the input time steps of the conditioning text inputs and the output time steps of the audio outputs.

7 . The method of claim 1 , wherein each discriminator comprises a discriminator neural network that comprises a sequence of groups of convolutional neural network layers, where one or more groups include one or more respective downsampling layers to account for a second ratio between the output time steps of the audio outputs and the input times steps of the conditioning text inputs.

8 . The method of claim 1 , wherein:

the feedforward generative neural network comprises a sequence of groups of convolutional neural network layers,

the method further comprises zero-padding each training conditioning text input to have a common dimensionality, and

the method further comprises processing a respective input to each convolutional neural network layer using a zero-one mask.

9 . The method of claim 1 , wherein:

each respective subset of the training audio output is a proper subset of the training audio output, and

at least two of the discriminators process different proper subsets of the training audio output.

10 . The method of claim 9 , wherein processing a respective proper subset of the training audio output comprises, for each discriminator:

taking a random sample of the training audio output, wherein the random sample comprises a plurality of consecutive audio samples, wherein a size of the random sample for a given discriminator is predetermined; and

processing the random sample of the training audio output.

11 . The method of claim 10 , wherein, for each conditional discriminator:

taking a random sample of the training audio output comprises taking a random sample that corresponds to a sequence of consecutive input time steps, and

processing the training conditioning text input comprises processing the training conditioning text input at the sequence of consecutive input time steps.

12 . The method of claim 10 , wherein processing the random sample of the training audio output comprises, for each discriminator, downsampling the random sample of the training audio output to generate a downsampled representation, wherein each discriminator downsamples the random sample by a predetermined downsampling factor.

13 . The method of claim 12 , wherein:

the respective predetermined downsampling factor for each discriminator corresponds to the size of the random sample for the discriminator; and

each downsampled representation has a common dimensionality for all of the discriminators.

14 . The method of claim 12 , wherein downsampling the random sample of the training audio output comprises processing the random sample of the training audio output using a strided convolutional neural network layer.

15 . The method of claim 1 , wherein the respective linguistic feature representation of the conditioning text input at each of the input time steps comprises one or more of: a phoneme, a duration, or a logarithmic fundamental frequency.

16 . The method of claim 1 , wherein the generative input further comprises a noise input.

17 . The method of claim 16 , wherein the feedforward generative neural network comprises one or more conditional batch normalization neural network layers that are conditioned on a linear embedding of the noise input.

18 . The method of claim 1 , wherein the generative input further comprises an identification of a class to which the audio output should belong.

19 . A system comprising one or more computers and one or more storage devices storing instructions that are operable, when executed by the one or more computers, to cause the one or more computers to perform operations comprising:

obtaining a training conditioning text input comprising a respective linguistic feature representation at each of a plurality of input time steps;

processing a training generative input comprising the training conditioning text input using a feedforward generative neural network, in accordance with current values of a plurality of generative parameters of the feedforward generative neural network, to generate a training audio output comprising respective audio samples at each of a plurality of output time steps;

processing the training audio output using each of a plurality of discriminators, wherein:

the plurality of discriminators comprises one or more conditional discriminators, wherein each conditional discriminator processes a respective subset of the training audio output and the training conditioning text input to generate a prediction of whether the training audio output is a real audio example or a synthetic audio example, and

the plurality of discriminators comprises one or more unconditional discriminators, wherein each unconditional discriminator processes a respective subset of the training audio output but not the training conditioning text input to generate a prediction of whether the training audio output is a real audio example or a synthetic audio example;

determining a first combined prediction by combining the respective predictions of the plurality of discriminators; and

determining an update to the current values of the generative parameters to increase a first error in the first combined prediction.

20 . One or more non-transitory computer storage media encoded with computer program instructions that when executed by a plurality of computers cause the plurality of computers to perform operations comprising:

obtaining a training conditioning text input comprising a respective linguistic feature representation at each of a plurality of input time steps;

processing a training generative input comprising the training conditioning text input using a feedforward generative neural network, in accordance with current values of a plurality of generative parameters of the feedforward generative neural network, to generate a training audio output comprising respective audio samples at each of a plurality of output time steps;

processing the training audio output using each of a plurality of discriminators, wherein:

the plurality of discriminators comprises one or more conditional discriminators, wherein each conditional discriminator processes a respective subset of the training audio output and the training conditioning text input to generate a prediction of whether the training audio output is a real audio example or a synthetic audio example, and

the plurality of discriminators comprises one or more unconditional discriminators, wherein each unconditional discriminator processes a respective subset of the training audio output but not the training conditioning text input to generate a prediction of whether the training audio output is a real audio example or a synthetic audio example;

determining a first combined prediction by combining the respective predictions of the plurality of discriminators; and

determining an update to the current values of the generative parameters to increase a first error in the first combined prediction.