#
Text2Video-Zero

Text2Video-Zero: Text-to-Image Diffusion Models are Zero-Shot Video Generators is by Levon Khachatryan, Andranik Movsisyan, Vahram Tadevosyan, Roberto Henschel, Zhangyang Wang, Shant Navasardyan, Humphrey Shi.

Text2Video-Zero enables zero-shot video generation using either:

1. A textual prompt
2. A prompt combined with guidance from poses or edges
3. Video Instruct-Pix2Pix (instruction-guided video editing)

Results are temporally consistent and closely follow the guidance and textual prompts.

The abstract from the paper is:

Recent text-to-video generation approaches rely on computationally heavy training and require large-scale video datasets. In this paper, we introduce a new task of zero-shot text-to-video generation and propose a low-cost approach (without any training or optimization) by leveraging the power of existing text-to-image synthesis methods (e.g., Stable Diffusion), making them suitable for the video domain. Our key modifications include (i) enriching the latent codes of the generated frames with motion dynamics to keep the global scene and the background time consistent; and (ii) reprogramming frame-level self-attention using a new cross-frame attention of each frame on the first frame, to preserve the context, appearance, and identity of the foreground object. Experiments show that this leads to low overhead, yet high-quality and remarkably consistent video generation. Moreover, our approach is not limited to text-to-video synthesis but is also applicable to other tasks such as conditional and content-specialized video generation, and Video Instruct-Pix2Pix, i.e., instruction-guided video editing. As experiments show, our method performs comparably or sometimes better than recent approaches, despite not being trained on additional video data.

You can find additional information about Text2Video-Zero on the project page, paper, and original codebase.

##
Usage example

###
Text-To-Video

To generate a video from prompt, run the following Python code:

    import torch
    from diffusers import TextToVideoZeroPipeline

    model_id = "runwayml/stable-diffusion-v1-5"
    pipe = TextToVideoZeroPipeline.from_pretrained(model_id, torch_dtype=torch.float16).to("cuda")

    prompt = "A panda is playing guitar on times square"
    result = pipe(prompt=prompt).images
    result = [(r * 255).astype("uint8") for r in result]
    imageio.mimsave("video.mp4", result, fps=4)

You can change these parameters in the pipeline call:

- Motion field strength (see the paper, Sect. 3.3.1):
  - `motion_field_strength_x` and `motion_field_strength_y`. Default: `motion_field_strength_x=12`, `motion_field_strength_y=12`
- `T` and `T'` (see the paper, Sect. 3.3.1)
  - `t0` and `t1` in the range `{0, ..., num_inference_steps}`. Default: `t0=45`, `t1=48`
- Video length:
  - `video_length`, the number of frames video_length to be generated. Default: `video_length=8`

We can also generate longer videos by doing the processing in a chunk-by-chunk manner:

    import torch
    from diffusers import TextToVideoZeroPipeline
    import numpy as np

    model_id = "runwayml/stable-diffusion-v1-5"
    pipe = TextToVideoZeroPipeline.from_pretrained(model_id, torch_dtype=torch.float16).to("cuda")
    seed = 0
    video_length = 24  #24 ÷ 4fps = 6 seconds
    chunk_size = 8
    prompt = "A panda is playing guitar on times square"

    # Generate the video chunk-by-chunk
    result = []
    chunk_ids = np.arange(0, video_length, chunk_size - 1)
    generator = torch.Generator(device="cuda")
    for i in range(len(chunk_ids)):
        print(f"Processing chunk {i + 1} / {len(chunk_ids)}")
        ch_start = chunk_ids[i]
        ch_end = video_length if i == len(chunk_ids) - 1 else chunk_ids[i + 1]
        # Attach the first frame for Cross Frame Attention
        frame_ids = [0] + list(range(ch_start, ch_end))
        # Fix the seed for the temporal consistency
        generator.manual_seed(seed)
        output = pipe(prompt=prompt, video_length=len(frame_ids), generator=generator, frame_ids=frame_ids)
        result.append(output.images[1:])

    # Concatenate chunks and save
    result = np.concatenate(result)
    result = [(r * 255).astype("uint8") for r in result]
    imageio.mimsave("video.mp4", result, fps=4)

- ####
  SDXL Support

  In order to use the SDXL model when generating a video from prompt, use the `TextToVideoZeroSDXLPipeline` pipeline:

    import torch
    from diffusers import TextToVideoZeroSDXLPipeline

    model_id = "stabilityai/stable-diffusion-xl-base-1.0"
    pipe = TextToVideoZeroSDXLPipeline.from_pretrained(
        model_id, torch_dtype=torch.float16, variant="fp16", use_safetensors=True
    ).to("cuda")

###
Text-To-Video with Pose Control

To generate a video from prompt with additional pose control

1. Download a demo video

       from huggingface_hub import hf_hub_download

       filename = "__assets__/poses_skeleton_gifs/dance1_corr.mp4"
       repo_id = "PAIR/Text2Video-Zero"
       video_path = hf_hub_download(repo_type="space", repo_id=repo_id, filename=filename)

2. Read video containing extracted pose images

       from PIL import Image
       import imageio

       reader = imageio.get_reader(video_path, "ffmpeg")
       frame_count = 8
       pose_images = [Image.fromarray(reader.get_data(i)) for i in range(frame_count)]

   To extract pose from actual video, read ControlNet documentation.

3. Run `StableDiffusionControlNetPipeline` with our custom attention processor

       import torch
       from diffusers import StableDiffusionControlNetPipeline, ControlNetModel
       from diffusers.pipelines.text_to_video_synthesis.pipeline_text_to_video_zero import CrossFrameAttnProcessor

       model_id = "runwayml/stable-diffusion-v1-5"
       controlnet = ControlNetModel.from_pretrained("lllyasviel/sd-controlnet-openpose", torch_dtype=torch.float16)
       pipe = StableDiffusionControlNetPipeline.from_pretrained(
           model_id, controlnet=controlnet, torch_dtype=torch.float16
       ).to("cuda")

       # Set the attention processor
       pipe.unet.set_attn_processor(CrossFrameAttnProcessor(batch_size=2))
       pipe.controlnet.set_attn_processor(CrossFrameAttnProcessor(batch_size=2))

       # fix latents for all frames
       latents = torch.randn((1, 4, 64, 64), device="cuda", dtype=torch.float16).repeat(len(pose_images), 1, 1, 1)

       prompt = "Darth Vader dancing in a desert"
       result = pipe(prompt=[prompt] * len(pose_images), image=pose_images, latents=latents).images
       imageio.mimsave("video.mp4", result, fps=4)

- ####
  SDXL Support

  Since our attention processor also works with SDXL, it can be utilized to generate a video from prompt using ControlNet models powered by SDXL:

      import torch
      from diffusers import StableDiffusionXLControlNetPipeline, ControlNetModel
      from diffusers.pipelines.text_to_video_synthesis.pipeline_text_to_video_zero import CrossFrameAttnProcessor

      controlnet_model_id = 'thibaud/controlnet-openpose-sdxl-1.0'
      model_id = 'stabilityai/stable-diffusion-xl-base-1.0'

      controlnet = ControlNetModel.from_pretrained(controlnet_model_id, torch_dtype=torch.float16)
      pipe = StableDiffusionControlNetPipeline.from_pretrained(
      	model_id, controlnet=controlnet, torch_dtype=torch.float16
      ).to('cuda')

      # Set the attention processor
      pipe.unet.set_attn_processor(CrossFrameAttnProcessor(batch_size=2))
      pipe.controlnet.set_attn_processor(CrossFrameAttnProcessor(batch_size=2))

      # fix latents for all frames
      latents = torch.randn((1, 4, 128, 128), device="cuda", dtype=torch.float16).repeat(len(pose_images), 1, 1, 1)

      prompt = "Darth Vader dancing in a desert"
      result = pipe(prompt=[prompt] * len(pose_images), image=pose_images, latents=latents).images
      imageio.mimsave("video.mp4", result, fps=4)

###
Text-To-Video with Edge Control

To generate a video from prompt with additional Canny edge control, follow the same steps described above for pose-guided generation using Canny edge ControlNet model.

###
Video Instruct-Pix2Pix

To perform text-guided video editing (with InstructPix2Pix):

1. Download a demo video

       from huggingface_hub import hf_hub_download

       filename = "__assets__/pix2pix video/camel.mp4"
       repo_id = "PAIR/Text2Video-Zero"
       video_path = hf_hub_download(repo_type="space", repo_id=repo_id, filename=filename)

2. Read video from path

       from PIL import Image
       import imageio

       reader = imageio.get_reader(video_path, "ffmpeg")
       frame_count = 8
       video = [Image.fromarray(reader.get_data(i)) for i in range(frame_count)]

3. Run `StableDiffusionInstructPix2PixPipeline` with our custom attention processor

       import torch
       from diffusers import StableDiffusionInstructPix2PixPipeline
       from diffusers.pipelines.text_to_video_synthesis.pipeline_text_to_video_zero import CrossFrameAttnProcessor

       model_id = "timbrooks/instruct-pix2pix"
       pipe = StableDiffusionInstructPix2PixPipeline.from_pretrained(model_id, torch_dtype=torch.float16).to("cuda")
       pipe.unet.set_attn_processor(CrossFrameAttnProcessor(batch_size=3))

       prompt = "make it Van Gogh Starry Night style"
       result = pipe(prompt=[prompt] * len(video), image=video).images
       imageio.mimsave("edited_video.mp4", result, fps=4)

###
DreamBooth specialization

Methods Text-To-Video, Text-To-Video with Pose Control and Text-To-Video with Edge Control can run with custom DreamBooth models, as shown below for Canny edge ControlNet model and Avatar style DreamBooth model:

1. Download a demo video

       from huggingface_hub import hf_hub_download

       filename = "__assets__/canny_videos_mp4/girl_turning.mp4"
       repo_id = "PAIR/Text2Video-Zero"
       video_path = hf_hub_download(repo_type="space", repo_id=repo_id, filename=filename)

2. Read video from path

       from PIL import Image
       import imageio

       reader = imageio.get_reader(video_path, "ffmpeg")
       frame_count = 8
       canny_edges = [Image.fromarray(reader.get_data(i)) for i in range(frame_count)]

3. Run `StableDiffusionControlNetPipeline` with custom trained DreamBooth model

       import torch
       from diffusers import StableDiffusionControlNetPipeline, ControlNetModel
       from diffusers.pipelines.text_to_video_synthesis.pipeline_text_to_video_zero import CrossFrameAttnProcessor

       # set model id to custom model
       model_id = "PAIR/text2video-zero-controlnet-canny-avatar"
       controlnet = ControlNetModel.from_pretrained("lllyasviel/sd-controlnet-canny", torch_dtype=torch.float16)
       pipe = StableDiffusionControlNetPipeline.from_pretrained(
           model_id, controlnet=controlnet, torch_dtype=torch.float16
       ).to("cuda")

       # Set the attention processor
       pipe.unet.set_attn_processor(CrossFrameAttnProcessor(batch_size=2))
       pipe.controlnet.set_attn_processor(CrossFrameAttnProcessor(batch_size=2))

       # fix latents for all frames
       latents = torch.randn((1, 4, 64, 64), device="cuda", dtype=torch.float16).repeat(len(canny_edges), 1, 1, 1)

       prompt = "oil painting of a beautiful girl avatar style"
       result = pipe(prompt=[prompt] * len(canny_edges), image=canny_edges, latents=latents).images
       imageio.mimsave("video.mp4", result, fps=4)

You can filter out some available DreamBooth-trained models with this link.

Make sure to check out the Schedulers guide to learn how to explore the tradeoff between scheduler speed and quality, and see the reuse components across pipelines section to learn how to efficiently load the same components into multiple pipelines.

##
TextToVideoZeroPipeline

###
class diffusers.TextToVideoZeroPipeline

< source >

( vae: AutoencoderKL text_encoder: CLIPTextModel tokenizer: CLIPTokenizer unet: UNet2DConditionModel scheduler: KarrasDiffusionSchedulers safety_checker: StableDiffusionSafetyChecker feature_extractor: CLIPImageProcessor requires_safety_checker: bool = True )

Parameters

- vae (AutoencoderKL) — Variational Auto-Encoder (VAE) Model to encode and decode images to and from latent representations.
- text_encoder (`CLIPTextModel`) — Frozen text-encoder (clip-vit-large-patch14).
- tokenizer (`CLIPTokenizer`) — A CLIPTokenizer to tokenize text.
- unet (UNet2DConditionModel) — A UNet3DConditionModel to denoise the encoded video latents.
- scheduler (SchedulerMixin) — A scheduler to be used in combination with `unet` to denoise the encoded image latents. Can be one of DDIMScheduler, LMSDiscreteScheduler, or PNDMScheduler.
- safety_checker (`StableDiffusionSafetyChecker`) — Classification module that estimates whether generated images could be considered offensive or harmful. Please refer to the model card for more details about a model’s potential harms.
- feature_extractor (`CLIPImageProcessor`) — A `CLIPImageProcessor` to extract features from generated images; used as inputs to the `safety_checker`.

Pipeline for zero-shot text-to-video generation using Stable Diffusion.

This model inherits from DiffusionPipeline. Check the superclass documentation for the generic methods implemented for all pipelines (downloading, saving, running on a particular device, etc.).

####
__call__

< source >

( prompt: typing.Union[str, typing.List[str]] video_length: typing.Optional[int] = 8 height: typing.Optional[int] = None width: typing.Optional[int] = None num_inference_steps: int = 50 guidance_scale: float = 7.5 negative_prompt: typing.Union[typing.List[str], str, NoneType] = None num_videos_per_prompt: typing.Optional[int] = 1 eta: float = 0.0 generator: typing.Union[torch._C.Generator, typing.List[torch._C.Generator], NoneType] = None latents: typing.Optional[torch.FloatTensor] = None motion_field_strength_x: float = 12 motion_field_strength_y: float = 12 output_type: typing.Optional[str] = 'tensor' return_dict: bool = True callback: typing.Union[typing.Callable[[int, int, torch.FloatTensor], NoneType], NoneType] = None callback_steps: typing.Optional[int] = 1 t0: int = 44 t1: int = 47 frame_ids: typing.Optional[typing.List[int]] = None ) →
TextToVideoPipelineOutput

Parameters

- prompt (`str` or `List[str]`, optional) — The prompt or prompts to guide image generation. If not defined, you need to pass `prompt_embeds`.
- video_length (`int`, optional, defaults to 8) — The number of generated video frames.
- height (`int`, optional, defaults to `self.unet.config.sample_size * self.vae_scale_factor`) — The height in pixels of the generated image.
- width (`int`, optional, defaults to `self.unet.config.sample_size * self.vae_scale_factor`) — The width in pixels of the generated image.
- num_inference_steps (`int`, optional, defaults to 50) — The number of denoising steps. More denoising steps usually lead to a higher quality image at the expense of slower inference.
- guidance_scale (`float`, optional, defaults to 7.5) — A higher guidance scale value encourages the model to generate images closely linked to the text `prompt` at the expense of lower image quality. Guidance scale is enabled when `guidance_scale > 1`.
- negative_prompt (`str` or `List[str]`, optional) — The prompt or prompts to guide what to not include in video generation. If not defined, you need to pass `negative_prompt_embeds` instead. Ignored when not using guidance (`guidance_scale < 1`).
- num_videos_per_prompt (`int`, optional, defaults to 1) — The number of videos to generate per prompt.
- eta (`float`, optional, defaults to 0.0) — Corresponds to parameter eta (η) from the DDIM paper. Only applies to the DDIMScheduler, and is ignored in other schedulers.
- generator (`torch.Generator` or `List[torch.Generator]`, optional) — A `torch.Generator` to make generation deterministic.
- latents (`torch.FloatTensor`, optional) — Pre-generated noisy latents sampled from a Gaussian distribution, to be used as inputs for video generation. Can be used to tweak the same generation with different prompts. If not provided, a latents tensor is generated by sampling using the supplied random `generator`.
- output_type (`str`, optional, defaults to `"numpy"`) — The output format of the generated video. Choose between `"latent"` and `"numpy"`.
- return_dict (`bool`, optional, defaults to `True`) — Whether or not to return a TextToVideoPipelineOutput instead of a plain tuple.
- callback (`Callable`, optional) — A function that calls every `callback_steps` steps during inference. The function is called with the following arguments: `callback(step: int, timestep: int, latents: torch.FloatTensor)`.
- callback_steps (`int`, optional, defaults to 1) — The frequency at which the `callback` function is called. If not specified, the callback is called at every step.
- motion_field_strength_x (`float`, optional, defaults to 12) — Strength of motion in generated video along x-axis. See the paper, Sect. 3.3.1.
- motion_field_strength_y (`float`, optional, defaults to 12) — Strength of motion in generated video along y-axis. See the paper, Sect. 3.3.1.
- t0 (`int`, optional, defaults to 44) — Timestep t0. Should be in the range [0, num_inference_steps - 1]. See the paper, Sect. 3.3.1.
- t1 (`int`, optional, defaults to 47) — Timestep t0. Should be in the range [t0 + 1, num_inference_steps - 1]. See the paper, Sect. 3.3.1.
- frame_ids (`List[int]`, optional) — Indexes of the frames that are being generated. This is used when generating longer videos chunk-by-chunk.

Returns

TextToVideoPipelineOutput

The output contains a `ndarray` of the generated video, when `output_type` != `"latent"`, otherwise a latent code of generated videos and a list of `bool`s indicating whether the corresponding generated video contains “not-safe-for-work” (nsfw) content..

The call function to the pipeline for generation.

####
backward_loop

< source >

( latents timesteps prompt_embeds guidance_scale callback callback_steps num_warmup_steps extra_step_kwargs cross_attention_kwargs = None ) →
latents

Parameters

- callback (`Callable`, optional) — A function that calls every `callback_steps` steps during inference. The function is called with the following arguments: `callback(step: int, timestep: int, latents: torch.FloatTensor)`.
- callback_steps (`int`, optional, defaults to 1) — The frequency at which the `callback` function is called. If not specified, the callback is called at every step. extra_step_kwargs — Extra_step_kwargs. cross_attention_kwargs — A kwargs dictionary that if specified is passed along to the `AttentionProcessor` as defined in `self.processor`. num_warmup_steps — number of warmup steps.

Returns

latents

Latents of backward process output at time timesteps[-1].

Perform backward process given list of time steps.

####
encode_prompt

< source >

( prompt device num_images_per_prompt do_classifier_free_guidance negative_prompt = None prompt_embeds: typing.Optional[torch.FloatTensor] = None negative_prompt_embeds: typing.Optional[torch.FloatTensor] = None lora_scale: typing.Optional[float] = None clip_skip: typing.Optional[int] = None )

Parameters

- prompt (`str` or `List[str]`, optional) — prompt to be encoded device — (`torch.device`): torch device
- num_images_per_prompt (`int`) — number of images that should be generated per prompt
- do_classifier_free_guidance (`bool`) — whether to use classifier free guidance or not
- negative_prompt (`str` or `List[str]`, optional) — The prompt or prompts not to guide the image generation. If not defined, one has to pass `negative_prompt_embeds` instead. Ignored when not using guidance (i.e., ignored if `guidance_scale` is less than `1`).
- prompt_embeds (`torch.FloatTensor`, optional) — Pre-generated text embeddings. Can be used to easily tweak text inputs, e.g. prompt weighting. If not provided, text embeddings will be generated from `prompt` input argument.
- negative_prompt_embeds (`torch.FloatTensor`, optional) — Pre-generated negative text embeddings. Can be used to easily tweak text inputs, e.g. prompt weighting. If not provided, negative_prompt_embeds will be generated from `negative_prompt` input argument.
- lora_scale (`float`, optional) — A LoRA scale that will be applied to all LoRA layers of the text encoder if LoRA layers are loaded.
- clip_skip (`int`, optional) — Number of layers to be skipped from CLIP while computing the prompt embeddings. A value of 1 means that the output of the pre-final layer will be used for computing the prompt embeddings.

Encodes the prompt into text encoder hidden states.

####
forward_loop

< source >

( x_t0 t0 t1 generator ) →
x_t1

Parameters

- generator (`torch.Generator` or `List[torch.Generator]`, optional) — A `torch.Generator` to make generation deterministic.

Returns

x_t1

Forward process applied to x_t0 from time t0 to t1.

Perform DDPM forward process from time t0 to t1. This is the same as adding noise with corresponding variance.

##
TextToVideoZeroSDXLPipeline

###
class diffusers.TextToVideoZeroSDXLPipeline

< source >

( vae: AutoencoderKL text_encoder: CLIPTextModel text_encoder_2: CLIPTextModelWithProjection tokenizer: CLIPTokenizer tokenizer_2: CLIPTokenizer unet: UNet2DConditionModel scheduler: KarrasDiffusionSchedulers image_encoder: CLIPVisionModelWithProjection = None feature_extractor: CLIPImageProcessor = None force_zeros_for_empty_prompt: bool = True add_watermarker: typing.Optional[bool] = None )

Parameters

- vae (AutoencoderKL) — Variational Auto-Encoder (VAE) Model to encode and decode images to and from latent representations.
- text_encoder (`CLIPTextModel`) — Frozen text-encoder. Stable Diffusion XL uses the text portion of CLIP, specifically the clip-vit-large-patch14 variant.
- text_encoder_2 (`CLIPTextModelWithProjection`) — Second frozen text-encoder. Stable Diffusion XL uses the text and pool portion of CLIP, specifically the laion/CLIP-ViT-bigG-14-laion2B-39B-b160k variant.
- tokenizer (`CLIPTokenizer`) — Tokenizer of class CLIPTokenizer.
- tokenizer_2 (`CLIPTokenizer`) — Second Tokenizer of class CLIPTokenizer.
- unet (UNet2DConditionModel) — Conditional U-Net architecture to denoise the encoded image latents.
- scheduler (SchedulerMixin) — A scheduler to be used in combination with `unet` to denoise the encoded image latents. Can be one of DDIMScheduler, LMSDiscreteScheduler, or PNDMScheduler.

Pipeline for zero-shot text-to-video generation using Stable Diffusion XL.

This model inherits from DiffusionPipeline. Check the superclass documentation for the generic methods implemented for all pipelines (downloading, saving, running on a particular device, etc.).

####
__call__

< source >

( prompt: typing.Union[str, typing.List[str]] prompt_2: typing.Union[typing.List[str], str, NoneType] = None video_length: typing.Optional[int] = 8 height: typing.Optional[int] = None width: typing.Optional[int] = None num_inference_steps: int = 50 denoising_end: typing.Optional[float] = None guidance_scale: float = 7.5 negative_prompt: typing.Union[typing.List[str], str, NoneType] = None negative_prompt_2: typing.Union[typing.List[str], str, NoneType] = None num_videos_per_prompt: typing.Optional[int] = 1 eta: float = 0.0 generator: typing.Union[torch._C.Generator, typing.List[torch._C.Generator], NoneType] = None frame_ids: typing.Optional[typing.List[int]] = None prompt_embeds: typing.Optional[torch.FloatTensor] = None negative_prompt_embeds: typing.Optional[torch.FloatTensor] = None pooled_prompt_embeds: typing.Optional[torch.FloatTensor] = None negative_pooled_prompt_embeds: typing.Optional[torch.FloatTensor] = None latents: typing.Optional[torch.FloatTensor] = None motion_field_strength_x: float = 12 motion_field_strength_y: float = 12 output_type: typing.Optional[str] = 'tensor' return_dict: bool = True callback: typing.Union[typing.Callable[[int, int, torch.FloatTensor], NoneType], NoneType] = None callback_steps: int = 1 cross_attention_kwargs: typing.Union[typing.Dict[str, typing.Any], NoneType] = None guidance_rescale: float = 0.0 original_size: typing.Union[typing.Tuple[int, int], NoneType] = None crops_coords_top_left: typing.Tuple[int, int] = (0, 0) target_size: typing.Union[typing.Tuple[int, int], NoneType] = None t0: int = 44 t1: int = 47 )

Parameters

- prompt (`str` or `List[str]`, optional) — The prompt or prompts to guide the image generation. If not defined, one has to pass `prompt_embeds`. instead.
- prompt_2 (`str` or `List[str]`, optional) — The prompt or prompts to be sent to the `tokenizer_2` and `text_encoder_2`. If not defined, `prompt` is used in both text-encoders
- video_length (`int`, optional, defaults to 8) — The number of generated video frames.
- height (`int`, optional, defaults to self.unet.config.sample_size * self.vae_scale_factor) — The height in pixels of the generated image.
- width (`int`, optional, defaults to self.unet.config.sample_size * self.vae_scale_factor) — The width in pixels of the generated image.
- num_inference_steps (`int`, optional, defaults to 50) — The number of denoising steps. More denoising steps usually lead to a higher quality image at the expense of slower inference.
- denoising_end (`float`, optional) — When specified, determines the fraction (between 0.0 and 1.0) of the total denoising process to be completed before it is intentionally prematurely terminated. As a result, the returned sample will still retain a substantial amount of noise as determined by the discrete timesteps selected by the scheduler. The denoising_end parameter should ideally be utilized when this pipeline forms a part of a “Mixture of Denoisers” multi-pipeline setup, as elaborated in Refining the Image Output
- guidance_scale (`float`, optional, defaults to 7.5) — Guidance scale as defined in Classifier-Free Diffusion Guidance. `guidance_scale` is defined as `w` of equation 2. of Imagen Paper. Guidance scale is enabled by setting `guidance_scale > 1`. Higher guidance scale encourages to generate images that are closely linked to the text `prompt`, usually at the expense of lower image quality.
- negative_prompt (`str` or `List[str]`, optional) — The prompt or prompts not to guide the image generation. If not defined, one has to pass `negative_prompt_embeds` instead. Ignored when not using guidance (i.e., ignored if `guidance_scale` is less than `1`).
- negative_prompt_2 (`str` or `List[str]`, optional) — The prompt or prompts not to guide the image generation to be sent to `tokenizer_2` and `text_encoder_2`. If not defined, `negative_prompt` is used in both text-encoders
- num_videos_per_prompt (`int`, optional, defaults to 1) — The number of videos to generate per prompt.
- eta (`float`, optional, defaults to 0.0) — Corresponds to parameter eta (η) in the DDIM paper: https://arxiv.org/abs/2010.02502. Only applies to schedulers.DDIMScheduler, will be ignored for others.
- generator (`torch.Generator` or `List[torch.Generator]`, optional) — One or a list of torch generator(s) to make generation deterministic.
- frame_ids (`List[int]`, optional) — Indexes of the frames that are being generated. This is used when generating longer videos chunk-by-chunk.
- prompt_embeds (`torch.FloatTensor`, optional) — Pre-generated text embeddings. Can be used to easily tweak text inputs, e.g. prompt weighting. If not provided, text embeddings will be generated from `prompt` input argument.
- negative_prompt_embeds (`torch.FloatTensor`, optional) — Pre-generated negative text embeddings. Can be used to easily tweak text inputs, e.g. prompt weighting. If not provided, negative_prompt_embeds will be generated from `negative_prompt` input argument.
- pooled_prompt_embeds (`torch.FloatTensor`, optional) — Pre-generated pooled text embeddings. Can be used to easily tweak text inputs, e.g. prompt weighting. If not provided, pooled text embeddings will be generated from `prompt` input argument.
- negative_pooled_prompt_embeds (`torch.FloatTensor`, optional) — Pre-generated negative pooled text embeddings. Can be used to easily tweak text inputs, e.g. prompt weighting. If not provided, pooled negative_prompt_embeds will be generated from `negative_prompt` input argument.
- latents (`torch.FloatTensor`, optional) — Pre-generated noisy latents, sampled from a Gaussian distribution, to be used as inputs for image generation. Can be used to tweak the same generation with different prompts. If not provided, a latents tensor will ge generated by sampling using the supplied random `generator`.
- motion_field_strength_x (`float`, optional, defaults to 12) — Strength of motion in generated video along x-axis. See the paper, Sect. 3.3.1.
- motion_field_strength_y (`float`, optional, defaults to 12) — Strength of motion in generated video along y-axis. See the paper, Sect. 3.3.1.
- output_type (`str`, optional, defaults to `"pil"`) — The output format of the generate image. Choose between PIL: `PIL.Image.Image` or `np.array`.
- return_dict (`bool`, optional, defaults to `True`) — Whether or not to return a `~pipelines.stable_diffusion_xl.StableDiffusionXLPipelineOutput` instead of a plain tuple.
- callback (`Callable`, optional) — A function that will be called every `callback_steps` steps during inference. The function will be called with the following arguments: `callback(step: int, timestep: int, latents: torch.FloatTensor)`.
- callback_steps (`int`, optional, defaults to 1) — The frequency at which the `callback` function will be called. If not specified, the callback will be called at every step.
- cross_attention_kwargs (`dict`, optional) — A kwargs dictionary that if specified is passed along to the `AttentionProcessor` as defined under `self.processor` in diffusers.cross_attention.
- guidance_rescale (`float`, optional, defaults to 0.7) — Guidance rescale factor proposed by Common Diffusion Noise Schedules and Sample Steps are Flawed `guidance_scale` is defined as `φ` in equation 16. of Common Diffusion Noise Schedules and Sample Steps are Flawed. Guidance rescale factor should fix overexposure when using zero terminal SNR.
- original_size (`Tuple[int]`, optional, defaults to (1024, 1024)) — If `original_size` is not the same as `target_size` the image will appear to be down- or upsampled. `original_size` defaults to `(width, height)` if not specified. Part of SDXL’s micro-conditioning as explained in section 2.2 of https://huggingface.co/papers/2307.01952.
- crops_coords_top_left (`Tuple[int]`, optional, defaults to (0, 0)) — `crops_coords_top_left` can be used to generate an image that appears to be “cropped” from the position `crops_coords_top_left` downwards. Favorable, well-centered images are usually achieved by setting `crops_coords_top_left` to (0, 0). Part of SDXL’s micro-conditioning as explained in section 2.2 of https://huggingface.co/papers/2307.01952.
- target_size (`Tuple[int]`, optional, defaults to (1024, 1024)) — For most cases, `target_size` should be set to the desired height and width of the generated image. If not specified it will default to `(width, height)`. Part of SDXL’s micro-conditioning as explained in section 2.2 of https://huggingface.co/papers/2307.01952.
- t0 (`int`, optional, defaults to 44) — Timestep t0. Should be in the range [0, num_inference_steps - 1]. See the paper, Sect. 3.3.1.
- t1 (`int`, optional, defaults to 47) — Timestep t0. Should be in the range [t0 + 1, num_inference_steps - 1]. See the paper, Sect. 3.3.1.

Function invoked when calling the pipeline for generation.

####
backward_loop

< source >

( latents timesteps prompt_embeds guidance_scale callback callback_steps num_warmup_steps extra_step_kwargs add_text_embeds add_time_ids cross_attention_kwargs = None guidance_rescale: float = 0.0 ) →
latents

Parameters

- callback (`Callable`, optional) — A function that calls every `callback_steps` steps during inference. The function is called with the following arguments: `callback(step: int, timestep: int, latents: torch.FloatTensor)`.
- callback_steps (`int`, optional, defaults to 1) — The frequency at which the `callback` function is called. If not specified, the callback is called at every step. extra_step_kwargs — Extra_step_kwargs. cross_attention_kwargs — A kwargs dictionary that if specified is passed along to the `AttentionProcessor` as defined in `self.processor`. num_warmup_steps — number of warmup steps.

Returns

latents

latents of backward process output at time timesteps[-1]

Perform backward process given list of time steps

####
disable_vae_slicing

< source >

( )

Disable sliced VAE decoding. If `enable_vae_slicing` was previously enabled, this method will go back to computing decoding in one step.

####
enable_vae_slicing

< source >

( )

Enable sliced VAE decoding. When this option is enabled, the VAE will split the input tensor in slices to compute decoding in several steps. This is useful to save some memory and allow larger batch sizes.

####
encode_prompt

< source >

( prompt: str prompt_2: typing.Optional[str] = None device: typing.Optional[torch.device] = None num_images_per_prompt: int = 1 do_classifier_free_guidance: bool = True negative_prompt: typing.Optional[str] = None negative_prompt_2: typing.Optional[str] = None prompt_embeds: typing.Optional[torch.FloatTensor] = None negative_prompt_embeds: typing.Optional[torch.FloatTensor] = None pooled_prompt_embeds: typing.Optional[torch.FloatTensor] = None negative_pooled_prompt_embeds: typing.Optional[torch.FloatTensor] = None lora_scale: typing.Optional[float] = None clip_skip: typing.Optional[int] = None )

Parameters

- prompt (`str` or `List[str]`, optional) — prompt to be encoded
- prompt_2 (`str` or `List[str]`, optional) — The prompt or prompts to be sent to the `tokenizer_2` and `text_encoder_2`. If not defined, `prompt` is used in both text-encoders device — (`torch.device`): torch device
- num_images_per_prompt (`int`) — number of images that should be generated per prompt
- do_classifier_free_guidance (`bool`) — whether to use classifier free guidance or not
- negative_prompt (`str` or `List[str]`, optional) — The prompt or prompts not to guide the image generation. If not defined, one has to pass `negative_prompt_embeds` instead. Ignored when not using guidance (i.e., ignored if `guidance_scale` is less than `1`).
- negative_prompt_2 (`str` or `List[str]`, optional) — The prompt or prompts not to guide the image generation to be sent to `tokenizer_2` and `text_encoder_2`. If not defined, `negative_prompt` is used in both text-encoders
- prompt_embeds (`torch.FloatTensor`, optional) — Pre-generated text embeddings. Can be used to easily tweak text inputs, e.g. prompt weighting. If not provided, text embeddings will be generated from `prompt` input argument.
- negative_prompt_embeds (`torch.FloatTensor`, optional) — Pre-generated negative text embeddings. Can be used to easily tweak text inputs, e.g. prompt weighting. If not provided, negative_prompt_embeds will be generated from `negative_prompt` input argument.
- pooled_prompt_embeds (`torch.FloatTensor`, optional) — Pre-generated pooled text embeddings. Can be used to easily tweak text inputs, e.g. prompt weighting. If not provided, pooled text embeddings will be generated from `prompt` input argument.
- negative_pooled_prompt_embeds (`torch.FloatTensor`, optional) — Pre-generated negative pooled text embeddings. Can be used to easily tweak text inputs, e.g. prompt weighting. If not provided, pooled negative_prompt_embeds will be generated from `negative_prompt` input argument.
- lora_scale (`float`, optional) — A lora scale that will be applied to all LoRA layers of the text encoder if LoRA layers are loaded.
- clip_skip (`int`, optional) — Number of layers to be skipped from CLIP while computing the prompt embeddings. A value of 1 means that the output of the pre-final layer will be used for computing the prompt embeddings.

Encodes the prompt into text encoder hidden states.

####
forward_loop

< source >

( x_t0 t0 t1 generator ) →
x_t1

Parameters

- generator (`torch.Generator` or `List[torch.Generator]`, optional) — A `torch.Generator` to make generation deterministic.

Returns

x_t1

Forward process applied to x_t0 from time t0 to t1.

Perform DDPM forward process from time t0 to t1. This is the same as adding noise with corresponding variance.

##
TextToVideoPipelineOutput

###
class diffusers.pipelines.text_to_video_synthesis.pipeline_text_to_video_zero.TextToVideoPipelineOutput

< source >

( images: typing.Union[typing.List[PIL.Image.Image], numpy.ndarray] nsfw_content_detected: typing.Optional[typing.List[bool]] )

Parameters

- images (`[List[PIL.Image.Image]`, `np.ndarray`]) — List of denoised PIL images of length `batch_size` or NumPy array of shape `(batch_size, height, width, num_channels)`.
- nsfw_content_detected (`[List[bool]]`) — List indicating whether the corresponding generated image contains “not-safe-for-work” (nsfw) content or `None` if safety checking could not be performed.

Output class for zero-shot text-to-video pipeline.