Support prompt timestep embeds and prompt cross attn modulation

src/diffusers/models/transformers/transformer_ltx2.py

@@ -1093,6 +1093,8 @@ class LTX2VideoTransformer3DModel(
         pos_embed_max_pos: int = 20,
         base_height: int = 2048,
         base_width: int = 2048,
+        gated_attn: bool = False,
+        cross_attn_mod: bool = False,
         audio_in_channels: int = 128,  # Audio Arguments
         audio_out_channels: int | None = 128,
         audio_patch_size: int = 1,
@@ -1104,6 +1106,8 @@ class LTX2VideoTransformer3DModel(
         audio_pos_embed_max_pos: int = 20,
         audio_sampling_rate: int = 16000,
         audio_hop_length: int = 160,
+        audio_gated_attn: bool = False,
+        audio_cross_attn_mod: bool = False,
         num_layers: int = 48,  # Shared arguments
         activation_fn: str = "gelu-approximate",
         qk_norm: str = "rms_norm_across_heads",
@@ -1118,6 +1122,7 @@ class LTX2VideoTransformer3DModel(
         timestep_scale_multiplier: int = 1000,
         cross_attn_timestep_scale_multiplier: int = 1000,
         rope_type: str = "interleaved",
+        prompt_modulation: bool = False,
     ) -> None:
         super().__init__()
 
@@ -1170,6 +1175,13 @@ class LTX2VideoTransformer3DModel(
         self.scale_shift_table = nn.Parameter(torch.randn(2, inner_dim) / inner_dim**0.5)
         self.audio_scale_shift_table = nn.Parameter(torch.randn(2, audio_inner_dim) / audio_inner_dim**0.5)
 
+        # 3.4. Prompt Scale/Shift Modulation parameters (LTX-2.3)
+        if prompt_modulation:
+            self.prompt_adaln = LTX2AdaLayerNormSingle(inner_dim, num_mod_params=2, use_additional_conditions=False)
+            self.audio_prompt_adaln = LTX2AdaLayerNormSingle(
+                inner_dim, num_mod_params=2, use_additional_conditions=False
+            )
+
         # 4. Rotary Positional Embeddings (RoPE)
         # Self-Attention
         self.rope = LTX2AudioVideoRotaryPosEmbed(
@@ -1246,6 +1258,10 @@ class LTX2VideoTransformer3DModel(
                     audio_num_attention_heads=audio_num_attention_heads,
                     audio_attention_head_dim=audio_attention_head_dim,
                     audio_cross_attention_dim=audio_cross_attention_dim,
+                    video_gated_attn=gated_attn,
+                    video_cross_attn_adaln=cross_attn_mod,
+                    audio_gated_attn=audio_gated_attn,
+                    audio_cross_attn_adaln=audio_cross_attn_mod,
                     qk_norm=qk_norm,
                     activation_fn=activation_fn,
                     attention_bias=attention_bias,
@@ -1276,6 +1292,8 @@ class LTX2VideoTransformer3DModel(
         audio_encoder_hidden_states: torch.Tensor,
         timestep: torch.LongTensor,
         audio_timestep: torch.LongTensor | None = None,
+        sigma: torch.Tensor | None = None,
+        audio_sigma: torch.Tensor | None = None,
         encoder_attention_mask: torch.Tensor | None = None,
         audio_encoder_attention_mask: torch.Tensor | None = None,
         self_attention_mask: torch.Tensor | None = None,
@@ -1307,6 +1325,13 @@ class LTX2VideoTransformer3DModel(
             audio_timestep (`torch.Tensor`, *optional*):
                 Input timestep of shape `(batch_size,)` or `(batch_size, num_audio_tokens)` for audio modulation
                 params. This is only used by certain pipelines such as the I2V pipeline.
+            sigma (`torch.Tensor`, *optional*):
+                Input scaled timestep of shape (batch_size,). Used for video prompt cross attention modulation in
+                models such as LTX-2.3.
+            audio_sigma (`torch.Tensor`, *optional*):
+                Input scaled timestep of shape (batch_size,). Used for audio prompt cross attention modulation in
+                models such as LTX-2.3. If `sigma` is supplied but `audio_sigma` is not, `audio_sigma` will be set to
+                the provided `sigma` value.
             encoder_attention_mask (`torch.Tensor`, *optional*):
                 Optional multiplicative text attention mask of shape `(batch_size, text_seq_len)`.
             audio_encoder_attention_mask (`torch.Tensor`, *optional*):
@@ -1343,6 +1368,7 @@ class LTX2VideoTransformer3DModel(
         """
         # Determine timestep for audio.
         audio_timestep = audio_timestep if audio_timestep is not None else timestep
+        audio_sigma = audio_sigma if audio_sigma is not None else sigma
 
         # convert encoder_attention_mask to a bias the same way we do for attention_mask
         if encoder_attention_mask is not None and encoder_attention_mask.ndim == 2:
@@ -1413,6 +1439,19 @@ class LTX2VideoTransformer3DModel(
         temb_audio = temb_audio.view(batch_size, -1, temb_audio.size(-1))
         audio_embedded_timestep = audio_embedded_timestep.view(batch_size, -1, audio_embedded_timestep.size(-1))
 
+        if self.config.prompt_modulation:
+            # LTX-2.3
+            temb_prompt, _ = self.prompt_adaln(
+                sigma.flatten(), batch_size=batch_size, hidden_dtype=hidden_states.dtype
+            )
+            temb_prompt_audio, _ = self.audio_prompt_adaln(
+                audio_sigma.flatten(), batch_size=batch_size, hidden_dtype=audio_hidden_states.dtype
+            )
+            temb_prompt = temb_prompt.view(batch_size, -1, temb_prompt.size(-1))
+            temb_prompt_audio = temb_prompt_audio.view(batch_size, -1, temb_prompt_audio.size(-1))
+        else:
+            temb_prompt = temb_prompt_audio = None
+
         # 3.2. Prepare global modality cross attention modulation parameters
         video_cross_attn_scale_shift, _ = self.av_cross_attn_video_scale_shift(
             timestep.flatten(),
@@ -1466,8 +1505,8 @@ class LTX2VideoTransformer3DModel(
                     audio_cross_attn_scale_shift,
                     video_cross_attn_a2v_gate,
                     audio_cross_attn_v2a_gate,
-                    None,  # temb_prompt
-                    None,  # temb_prompt_audio
+                    temb_prompt,
+                    temb_prompt_audio,
                     video_rotary_emb,
                     audio_rotary_emb,
                     video_cross_attn_rotary_emb,
@@ -1487,8 +1526,8 @@ class LTX2VideoTransformer3DModel(
                     temb_ca_audio_scale_shift=audio_cross_attn_scale_shift,
                     temb_ca_gate=video_cross_attn_a2v_gate,
                     temb_ca_audio_gate=audio_cross_attn_v2a_gate,
-                    temb_prompt=None,
-                    temb_prompt_audio=None,
+                    temb_prompt=temb_prompt,
+                    temb_prompt_audio=temb_prompt_audio,
                     video_rotary_emb=video_rotary_emb,
                     audio_rotary_emb=audio_rotary_emb,
                     ca_video_rotary_emb=video_cross_attn_rotary_emb,