Vocoder_Layers.py

from Imports import *
from Configuration import *

def ResBlock_v1(x, filters, kernel_size, dilation_rates=(1, 3, 5)):
    """
    Standard HiFi-GAN ResBlock. Contains 3 cycles of convolutions.
    """
    for d in dilation_rates:
        shortcut = x
        # Sub-cycle 1
        x = layers.LeakyReLU(0.1)(x)
        x = layers.Conv1D(filters, kernel_size, dilation_rate=d, padding='same')(x)
        # Sub-cycle 2
        x = layers.LeakyReLU(0.1)(x)
        x = layers.Conv1D(filters, kernel_size, dilation_rate=1, padding='same')(x)
        # Residual connection
        x = x + shortcut
    return x

def MRF_Module(x, filters):
    """
    Multi-Receptive Field Fusion. 
    Runs 3 ResBlocks in parallel and averages their output.
    """
    # Parallel paths with kernel sizes 3, 7, and 11
    res1 = ResBlock_v1(x, filters, kernel_size=3, dilation_rates=(1, 3, 5))
    res2 = ResBlock_v1(x, filters, kernel_size=7, dilation_rates=(1, 3, 5))
    res3 = ResBlock_v1(x, filters, kernel_size=11, dilation_rates=(1, 3, 5))
    
    # Average the three paths (or Add, then divide by 3)
    return (res1 + res2 + res3) / 3

def build_generator(input_shape=(None, 80)):
    mel_input = keras.layers.Input(shape=input_shape)  # [B, T_mel, 80]
    
    # Initial Convolution
    x = layers.Conv1D(512, kernel_size=7, padding='same')(mel_input)
    
    # Standard HiFi-GAN upsampling ratios: [8, 8, 2, 2]
    # Standard channels: [256, 128, 64, 32]
    upsample_rates = [8, 8, 2, 2]
    upsample_kernels = [16, 16, 4, 4]
    channels = [256, 128, 64, 32]

    for i in range(len(upsample_rates)):
        x = layers.LeakyReLU(0.1)(x)
        # Upsample
        x = layers.Conv1DTranspose(
            channels[i], 
            kernel_size=upsample_kernels[i], 
            strides=upsample_rates[i], 
            padding='same'
        )(x)
        # Apply Multi-Receptive Field Fusion (Parallel blocks)
        x = MRF_Module(x, channels[i])

    # Final output layer
    x = layers.LeakyReLU(0.1)(x)
    x = layers.Conv1D(1, kernel_size=7, padding='same', activation='tanh')(x)
    
    return keras.models.Model(mel_input, x, name="HiFiGAN_Generator_V1")