src/sbv2/posterior_encoder.py

import torch
import torch.nn as nn
import torch.nn.functional as F

class ResidualCouplingLayer(nn.Module):
    def __init__(self, spec_channels, inter_channels, hidden_channels, kernel_size, enc_dilation_rate, n_layers, p_dropout):
        super().__init__()
        self.channels = channels
        self.hidden_channels = hidden_channels
        self.kernel_size = kernel_size
        self.dilation_rate = dilation_rate
        self.n_layers = n_layers

        self.pre = nn.Conv1d(channels // 2, hidden_channels, 1)
        self.convs = nn.ModuleList()
        for i in range(n_layers):
            dilation = dilation_rate ** i
            self.convs.append(
                nn.Conv1d(hidden_channels, hidden_channels, kernel_size, padding=(kernel_size-1)//2 * dilation, dilation=dilation)
            )
        self.post = nn.Conv1d(hidden_channels, channels, 1)

    def forward(self, x, reverse=False):
        x0, x1 = torch.chunk(x, 2, dim=1)
        h = self.pre(x0)
        for conv in self.convs:
            h = F.relu(conv(h))
        h = self.post(h)
        m, logs = torch.chunk(h, 2, dim=1)

        if not reverse:
            x1 = m + x1 * torch.exp(logs)
        else:
            x1 = (x1 - m) * torch.exp(-logs)

        return torch.cat([x0, x1], dim=1)

class ResidualCouplingBlock(nn.Module):
    def __init__(self, channels, hidden_channels, kernel_size, dilation_rate, n_layers, n_flows):
        super().__init__()
        self.flows = nn.ModuleList()
        for _ in range(n_flows):
            self.flows.append(ResidualCouplingLayer(channels, hidden_channels, kernel_size, dilation_rate, n_layers))
            self.flows.append(Flip())

    def forward(self, x, reverse=False):
        if not reverse:
            for flow in self.flows:
                x = flow(x)
        else:
            for flow in reversed(self.flows):
                x = flow(x, reverse=True)
        return x

class Flip(nn.Module):
    def __init__(self):
        super().__init__()

    def forward(self, x, reverse=False):
        return x.flip(1)

class PosteriorEncoder(nn.Module):
    def __init__(self, in_channels, out_channels, hidden_channels, kernel_size, dilation_rate, n_layers):
        super().__init__()
        self.pre = nn.Conv1d(in_channels, hidden_channels, 1)
        self.convs = nn.ModuleList()
        for i in range(n_layers):
            dilation = dilation_rate ** i
            self.convs.append(
                nn.Conv1d(hidden_channels, hidden_channels, kernel_size, padding=(kernel_size-1)//2 * dilation, dilation=dilation)
            )
        self.proj_mean = nn.Conv1d(hidden_channels, out_channels, 1)
        self.proj_logvar = nn.Conv1d(hidden_channels, out_channels, 1)

    def forward(self, x, x_lengths):
        x = self.pre(x)
        for conv in self.convs:
            x = F.relu(conv(x))
        m = self.proj_mean(x)
        logs = self.proj_logvar(x)
        z = m + torch.randn_like(m) * torch.exp(logs)
        return z, m, logs

    def infer(self, z, z_lengths):
        return z