Create model/backbones/mmdit.py

model/backbones/mmdit.py

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+"""
+ein notation:
+b - batch
+n - sequence
+nt - text sequence
+nw - raw wave length
+d - dimension
+"""
+
+from __future__ import annotations
+
+import torch
+from torch import nn
+
+from einops import repeat
+
+from x_transformers.x_transformers import RotaryEmbedding
+
+from model.modules import (
+    TimestepEmbedding,
+    ConvPositionEmbedding,
+    MMDiTBlock,
+    AdaLayerNormZero_Final,
+    precompute_freqs_cis, get_pos_embed_indices,
+)
+
+
+# text embedding
+
+class TextEmbedding(nn.Module):
+    def __init__(self, out_dim, text_num_embeds):
+        super().__init__()
+        self.text_embed = nn.Embedding(text_num_embeds + 1, out_dim)  # will use 0 as filler token
+
+        self.precompute_max_pos = 1024
+        self.register_buffer("freqs_cis", precompute_freqs_cis(out_dim, self.precompute_max_pos), persistent=False)
+
+    def forward(self, text: int['b nt'], drop_text = False) -> int['b nt d']:
+        text = text + 1
+        if drop_text:
+            text = torch.zeros_like(text)
+        text = self.text_embed(text)
+
+        # sinus pos emb
+        batch_start = torch.zeros((text.shape[0],), dtype=torch.long)
+        batch_text_len = text.shape[1]
+        pos_idx = get_pos_embed_indices(batch_start, batch_text_len, max_pos=self.precompute_max_pos)
+        text_pos_embed = self.freqs_cis[pos_idx]
+
+        text = text + text_pos_embed
+
+        return text
+
+
+# noised input & masked cond audio embedding
+
+class AudioEmbedding(nn.Module):
+    def __init__(self, in_dim, out_dim):
+        super().__init__()
+        self.linear = nn.Linear(2 * in_dim, out_dim)
+        self.conv_pos_embed = ConvPositionEmbedding(out_dim)
+
+    def forward(self, x: float['b n d'], cond: float['b n d'], drop_audio_cond = False):
+        if drop_audio_cond:
+            cond = torch.zeros_like(cond)
+        x = torch.cat((x, cond), dim = -1)
+        x = self.linear(x)
+        x = self.conv_pos_embed(x) + x
+        return x
+    
+
+# Transformer backbone using MM-DiT blocks
+
+class MMDiT(nn.Module):
+    def __init__(self, *, 
+                 dim, depth = 8, heads = 8, dim_head = 64, dropout = 0.1, ff_mult = 4,
+                 text_num_embeds = 256, mel_dim = 100,
+    ):
+        super().__init__()
+
+        self.time_embed = TimestepEmbedding(dim)
+        self.text_embed = TextEmbedding(dim, text_num_embeds)
+        self.audio_embed = AudioEmbedding(mel_dim, dim)
+
+        self.rotary_embed = RotaryEmbedding(dim_head)
+
+        self.dim = dim
+        self.depth = depth
+        
+        self.transformer_blocks = nn.ModuleList(
+            [
+                MMDiTBlock(
+                    dim = dim,
+                    heads = heads,
+                    dim_head = dim_head,
+                    dropout = dropout,
+                    ff_mult = ff_mult,
+                    context_pre_only = i == depth - 1,
+                )
+                for i in range(depth)
+            ]
+        )
+        self.norm_out = AdaLayerNormZero_Final(dim)  # final modulation
+        self.proj_out = nn.Linear(dim, mel_dim)
+
+    def forward(
+        self,
+        x: float['b n d'],     # nosied input audio
+        cond: float['b n d'],  # masked cond audio
+        text: int['b nt'],     # text
+        time: float['b'] | float[''],  # time step
+        drop_audio_cond,  # cfg for cond audio
+        drop_text,        # cfg for text
+        mask: bool['b n'] | None = None,
+    ):
+        batch = x.shape[0]
+        if time.ndim == 0:
+            time = repeat(time, ' -> b', b = batch)
+
+        # t: conditioning (time), c: context (text + masked cond audio), x: noised input audio
+        t = self.time_embed(time)
+        c = self.text_embed(text, drop_text = drop_text)
+        x = self.audio_embed(x, cond, drop_audio_cond = drop_audio_cond)
+
+        seq_len = x.shape[1]
+        text_len = text.shape[1]
+        rope_audio = self.rotary_embed.forward_from_seq_len(seq_len)
+        rope_text = self.rotary_embed.forward_from_seq_len(text_len)
+        
+        for block in self.transformer_blocks:
+            c, x = block(x, c, t, mask = mask, rope = rope_audio, c_rope = rope_text)
+
+        x = self.norm_out(x, t)
+        output = self.proj_out(x)
+
+        return output