fixed bug in defining embed dim for UNet1D (#12111)

* fixed bug in defining embed dim

* matched 1d temb process to 2d

* Update src/diffusers/models/unets/unet_1d.py
Co-authored-by: Dhruv Nair <dhruv.nair@gmail.com>

---------
Co-authored-by: Dhruv Nair <dhruv.nair@gmail.com>

src/diffusers/models/unets/unet_1d.py

@@ -82,6 +82,7 @@ class UNet1DModel(ModelMixin, ConfigMixin):
         out_channels: int = 2,
         extra_in_channels: int = 0,
         time_embedding_type: str = "fourier",
+        time_embedding_dim: Optional[int] = None,
         flip_sin_to_cos: bool = True,
         use_timestep_embedding: bool = False,
         freq_shift: float = 0.0,
@@ -100,15 +101,23 @@ class UNet1DModel(ModelMixin, ConfigMixin):
 
         # time
         if time_embedding_type == "fourier":
+            time_embed_dim = time_embedding_dim or block_out_channels[0] * 2
+            if time_embed_dim % 2 != 0:
+                raise ValueError(f"`time_embed_dim` should be divisible by 2, but is {time_embed_dim}.")
             self.time_proj = GaussianFourierProjection(
-                embedding_size=8, set_W_to_weight=False, log=False, flip_sin_to_cos=flip_sin_to_cos
+                embedding_size=time_embed_dim // 2, set_W_to_weight=False, log=False, flip_sin_to_cos=flip_sin_to_cos
             )
-            timestep_input_dim = 2 * block_out_channels[0]
+            timestep_input_dim = time_embed_dim
         elif time_embedding_type == "positional":
+            time_embed_dim = time_embedding_dim or block_out_channels[0] * 4
             self.time_proj = Timesteps(
                 block_out_channels[0], flip_sin_to_cos=flip_sin_to_cos, downscale_freq_shift=freq_shift
             )
             timestep_input_dim = block_out_channels[0]
+        else:
+            raise ValueError(
+                f"{time_embedding_type} does not exist. Please make sure to use one of `fourier` or `positional`."
+            )
 
         if use_timestep_embedding:
             time_embed_dim = block_out_channels[0] * 4