Mochi docs (#9934)

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Co-authored-by: Sayak Paul <spsayakpaul@gmail.com>

docs/source/en/api/pipelines/mochi.md

@@ -13,7 +13,7 @@
 # limitations under the License.
 -->
 
-# Mochi
+# Mochi 1 Preview
 
 [Mochi 1 Preview](https://huggingface.co/genmo/mochi-1-preview) from Genmo.
 
@@ -25,6 +25,201 @@ Make sure to check out the Schedulers [guide](../../using-diffusers/schedulers.m
 
 </Tip>
 
+## Generating videos with Mochi-1 Preview
+
+The following example will download the full precision `mochi-1-preview` weights and produce the highest quality results but will require at least 42GB VRAM to run.
+
+```python
+import torch
+from diffusers import MochiPipeline
+from diffusers.utils import export_to_video
+
+pipe = MochiPipeline.from_pretrained("genmo/mochi-1-preview")
+
+# Enable memory savings
+pipe.enable_model_cpu_offload()
+pipe.enable_vae_tiling()
+
+prompt = "Close-up of a chameleon's eye, with its scaly skin changing color. Ultra high resolution 4k."
+
+with torch.autocast("cuda", torch.bfloat16, cache_enabled=False):
+      frames = pipe(prompt, num_frames=85).frames[0]
+
+export_to_video(frames, "mochi.mp4", fps=30)
+```
+
+## Using a lower precision variant to save memory
+
+The following example will use the `bfloat16` variant of the model and requires 22GB VRAM to run. There is a slight drop in the quality of the generated video as a result.
+
+```python
+import torch
+from diffusers import MochiPipeline
+from diffusers.utils import export_to_video
+
+pipe = MochiPipeline.from_pretrained("genmo/mochi-1-preview", variant="bf16", torch_dtype=torch.bfloat16)
+
+# Enable memory savings
+pipe.enable_model_cpu_offload()
+pipe.enable_vae_tiling()
+
+prompt = "Close-up of a chameleon's eye, with its scaly skin changing color. Ultra high resolution 4k."
+frames = pipe(prompt, num_frames=85).frames[0]
+
+export_to_video(frames, "mochi.mp4", fps=30)
+```
+
+## Reproducing the results from the Genmo Mochi repo
+
+The [Genmo Mochi implementation](https://github.com/genmoai/mochi/tree/main) uses different precision values for each stage in the inference process. The text encoder and VAE use `torch.float32`, while the DiT uses `torch.bfloat16` with the [attention kernel](https://pytorch.org/docs/stable/generated/torch.nn.attention.sdpa_kernel.html#torch.nn.attention.sdpa_kernel) set to `EFFICIENT_ATTENTION`. Diffusers pipelines currently do not support setting different `dtypes` for different stages of the pipeline. In order to run inference in the same way as the the original implementation, please refer to the following example.
+
+<Tip>
+The original Mochi implementation zeros out empty prompts. However, enabling this option and placing the entire pipeline under autocast can lead to numerical overflows with the T5 text encoder.
+
+When enabling `force_zeros_for_empty_prompt`, it is recommended to run the text encoding step outside the autocast context in full precision.
+</Tip>
+
+<Tip>
+Decoding the latents in full precision is very memory intensive. You will need at least 70GB VRAM to generate the 163 frames in this example. To reduce memory, either reduce the number of frames or run the decoding step in `torch.bfloat16`.
+</Tip>
+
+```python
+import torch
+from torch.nn.attention import SDPBackend, sdpa_kernel
+
+from diffusers import MochiPipeline
+from diffusers.utils import export_to_video
+from diffusers.video_processor import VideoProcessor
+
+pipe = MochiPipeline.from_pretrained("genmo/mochi-1-preview", force_zeros_for_empty_prompt=True)
+pipe.enable_vae_tiling()
+pipe.enable_model_cpu_offload()
+
+prompt =  "An aerial shot of a parade of elephants walking across the African savannah. The camera showcases the herd and the surrounding landscape."
+
+with torch.no_grad():
+    prompt_embeds, prompt_attention_mask, negative_prompt_embeds, negative_prompt_attention_mask = (
+        pipe.encode_prompt(prompt=prompt)
+    )
+
+with torch.autocast("cuda", torch.bfloat16):
+    with sdpa_kernel(SDPBackend.EFFICIENT_ATTENTION):
+        frames = pipe(
+            prompt_embeds=prompt_embeds,
+            prompt_attention_mask=prompt_attention_mask,
+            negative_prompt_embeds=negative_prompt_embeds,
+            negative_prompt_attention_mask=negative_prompt_attention_mask,
+            guidance_scale=4.5,
+            num_inference_steps=64,
+            height=480,
+            width=848,
+            num_frames=163,
+            generator=torch.Generator("cuda").manual_seed(0),
+            output_type="latent",
+            return_dict=False,
+        )[0]
+
+video_processor = VideoProcessor(vae_scale_factor=8)
+has_latents_mean = hasattr(pipe.vae.config, "latents_mean") and pipe.vae.config.latents_mean is not None
+has_latents_std = hasattr(pipe.vae.config, "latents_std") and pipe.vae.config.latents_std is not None
+if has_latents_mean and has_latents_std:
+    latents_mean = (
+        torch.tensor(pipe.vae.config.latents_mean).view(1, 12, 1, 1, 1).to(frames.device, frames.dtype)
+    )
+    latents_std = (
+        torch.tensor(pipe.vae.config.latents_std).view(1, 12, 1, 1, 1).to(frames.device, frames.dtype)
+    )
+    frames = frames * latents_std / pipe.vae.config.scaling_factor + latents_mean
+else:
+    frames = frames / pipe.vae.config.scaling_factor
+
+with torch.no_grad():
+    video = pipe.vae.decode(frames.to(pipe.vae.dtype), return_dict=False)[0]
+
+video = video_processor.postprocess_video(video)[0]
+export_to_video(video, "mochi.mp4", fps=30)
+```
+
+## Running inference with multiple GPUs
+
+It is possible to split the large Mochi transformer across multiple GPUs using the `device_map` and `max_memory` options in `from_pretrained`. In the following example we split the model across two GPUs, each with 24GB of VRAM.
+
+```python
+import torch
+from diffusers import MochiPipeline, MochiTransformer3DModel
+from diffusers.utils import export_to_video
+
+model_id = "genmo/mochi-1-preview"
+transformer = MochiTransformer3DModel.from_pretrained(
+    model_id,
+    subfolder="transformer",
+    device_map="auto",
+    max_memory={0: "24GB", 1: "24GB"}
+)
+
+pipe = MochiPipeline.from_pretrained(model_id,  transformer=transformer)
+pipe.enable_model_cpu_offload()
+pipe.enable_vae_tiling()
+
+with torch.autocast(device_type="cuda", dtype=torch.bfloat16, cache_enabled=False):
+    frames = pipe(
+        prompt="Close-up of a chameleon's eye, with its scaly skin changing color. Ultra high resolution 4k.",
+        negative_prompt="",
+        height=480,
+        width=848,
+        num_frames=85,
+        num_inference_steps=50,
+        guidance_scale=4.5,
+        num_videos_per_prompt=1,
+        generator=torch.Generator(device="cuda").manual_seed(0),
+        max_sequence_length=256,
+        output_type="pil",
+    ).frames[0]
+
+export_to_video(frames, "output.mp4", fps=30)
+```
+
+## Using single file loading with the Mochi Transformer
+
+You can use `from_single_file` to load the Mochi transformer in its original format.
+
+<Tip>
+Diffusers currently doesn't support using the FP8 scaled versions of the Mochi single file checkpoints.
+</Tip>
+
+```python
+import torch
+from diffusers import MochiPipeline, MochiTransformer3DModel
+from diffusers.utils import export_to_video
+
+model_id = "genmo/mochi-1-preview"
+
+ckpt_path = "https://huggingface.co/Comfy-Org/mochi_preview_repackaged/blob/main/split_files/diffusion_models/mochi_preview_bf16.safetensors"
+
+transformer = MochiTransformer3DModel.from_pretrained(ckpt_path, torch_dtype=torch.bfloat16)
+
+pipe = MochiPipeline.from_pretrained(model_id,  transformer=transformer)
+pipe.enable_model_cpu_offload()
+pipe.enable_vae_tiling()
+
+with torch.autocast(device_type="cuda", dtype=torch.bfloat16, cache_enabled=False):
+    frames = pipe(
+        prompt="Close-up of a chameleon's eye, with its scaly skin changing color. Ultra high resolution 4k.",
+        negative_prompt="",
+        height=480,
+        width=848,
+        num_frames=85,
+        num_inference_steps=50,
+        guidance_scale=4.5,
+        num_videos_per_prompt=1,
+        generator=torch.Generator(device="cuda").manual_seed(0),
+        max_sequence_length=256,
+        output_type="pil",
+    ).frames[0]
+
+export_to_video(frames, "output.mp4", fps=30)
+```
+
 ## MochiPipeline
 
 [[autodoc]] MochiPipeline