import os import imageio import numpy as np from typing import Union import torch import torchvision from tqdm import tqdm from einops import rearrange def save_videos_grid(videos: torch.Tensor, path: str, rescale=False, n_rows=6, fps=8): videos = rearrange(videos, "b c t h w -> t b c h w") outputs = [] for x in videos: x = torchvision.utils.make_grid(x, nrow=n_rows) x = x.transpose(0, 1).transpose(1, 2).squeeze(-1) if rescale: x = (x + 1.0) / 2.0 # -1,1 -> 0,1 x = (x * 255).numpy().astype(np.uint8) outputs.append(x) os.makedirs(os.path.dirname(path), exist_ok=True) imageio.mimsave(path, outputs, fps=fps) # DDIM Inversion @torch.no_grad() def init_prompt(prompt, pipeline): uncond_input = pipeline.tokenizer( [""], padding="max_length", max_length=pipeline.tokenizer.model_max_length, return_tensors="pt" ) uncond_embeddings = pipeline.text_encoder(uncond_input.input_ids.to(pipeline.device))[0] text_input = pipeline.tokenizer( [prompt], padding="max_length", max_length=pipeline.tokenizer.model_max_length, truncation=True, return_tensors="pt", ) text_embeddings = pipeline.text_encoder(text_input.input_ids.to(pipeline.device))[0] context = torch.cat([uncond_embeddings, text_embeddings]) return context def next_step(model_output: Union[torch.FloatTensor, np.ndarray], timestep: int, sample: Union[torch.FloatTensor, np.ndarray], ddim_scheduler): timestep, next_timestep = min( timestep - ddim_scheduler.config.num_train_timesteps // ddim_scheduler.num_inference_steps, 999), timestep alpha_prod_t = ddim_scheduler.alphas_cumprod[timestep] if timestep >= 0 else ddim_scheduler.final_alpha_cumprod alpha_prod_t_next = ddim_scheduler.alphas_cumprod[next_timestep] beta_prod_t = 1 - alpha_prod_t next_original_sample = (sample - beta_prod_t ** 0.5 * model_output) / alpha_prod_t ** 0.5 next_sample_direction = (1 - alpha_prod_t_next) ** 0.5 * model_output next_sample = alpha_prod_t_next ** 0.5 * next_original_sample + next_sample_direction return next_sample def get_noise_pred_single(latents, t, context, unet): noise_pred = unet(latents, t, encoder_hidden_states=context)["sample"] return noise_pred @torch.no_grad() def ddim_loop(pipeline, ddim_scheduler, latent, num_inv_steps, prompt): context = init_prompt(prompt, pipeline) uncond_embeddings, cond_embeddings = context.chunk(2) all_latent = [latent] latent = latent.clone().detach() for i in tqdm(range(num_inv_steps)): t = ddim_scheduler.timesteps[len(ddim_scheduler.timesteps) - i - 1] noise_pred = get_noise_pred_single(latent, t, cond_embeddings, pipeline.unet) latent = next_step(noise_pred, t, latent, ddim_scheduler) all_latent.append(latent) return all_latent @torch.no_grad() def ddim_inversion(pipeline, ddim_scheduler, video_latent, num_inv_steps, prompt=""): ddim_latents = ddim_loop(pipeline, ddim_scheduler, video_latent, num_inv_steps, prompt) return ddim_latents