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Sayak Paul 77c13f8a49 [tests] refactor ltx2 dfr pipeline tests (#14655)
* Add LTX-2.5 DFR pipeline with generated keyframe slots

Ports DFRPipeline from the Lightricks reference. Stage 1 generates video plus
single-pixel-frame keyframe slots at a fraction of the requested resolution on
a VAE-aligned segment grid; both are spatially latent-upsampled and stage 2
re-denoises at twice that resolution with the slots re-attached and an optional
spatial detailing IC-LoRA active for that stage only. Optional temporal x2/x4
refine rounds tile the canvas at shared keyframes and densify with ancestral
Euler. With spatial_upscalings=2 a full-resolution detailing epilogue follows
the rounds.

The transformer already stored keyframes_abs_pos_embedding for load/save; this
wires it into the forward through a new video_keyframes_mask argument, which
only a keyframes-aware pipeline passes, so other pipelines are unaffected.

The epilogue denoises the whole canvas in one loop and tiles the transformer
call inside it, so every Euler step steps a canvas whose tiles have already
agreed on their overlaps. Spatial tiles blend under a trapezoidal mask, since
neither side of a height or width border holds a known answer. Temporal tiles
are cut on the keyframe seams the last refine round stitched on: both windows
reproduce a shared keyframe there, so the later one drops its run-up under a
rectangular mask rather than averaging it. Conditionings are attached once on
the whole canvas and filtered per tile at the token level, and a keyframe two
windows share is one token they both read.

The epilogue is handed its keyframes rather than asked to generate them. Each
carry plane is decoded on its own -- the VAE is causal, so a stacked decode
would bleed neighbours -- then Lanczos-stretched x2 in RGB and encoded again at
the output resolution, and pinned fully clean. Only the video latent is
spatially upsampled.

Conditioning fps is snapped to 60 above 30 rather than merely capped there, at
every stage. RoPE time is pixel_frame / fps, and the transformer is trained
around 24/25/30 and 60; a temporal round taking 24 fps to 48 lands between
those, and it shows as stutter at the latent borders. Playback fps is
unchanged, so 24 fps with one round still ships 48 fps.

A condition's index is read on the canvas num_frames asks for, and the moment
it names is carried onto each refine round's longer canvas by scaling its pixel
position by 2**round. The scaled position does not generally land on a latent
boundary, so it travels as a pixel index rather than through the public latent
index; a keyframe conditioning is appended as extra tokens instead of being
spliced into the base grid, so it does not need to.

height and width must be divisible by 2**spatial_upscalings times the VAE's
spatial compression ratio, which makes 4K 3840x2176 rather than 3840x2160. That
rule is checked ahead of the looser one every LTX-2 pipeline applies, so the
error names the divisor a DFR caller actually has to satisfy.

Four details are easy to get wrong, and each is covered by a test after showing
up as a visible seam at a tile handover:

- The ancestral step injects noise into every token, so the conditioning blend
  has to be re-applied afterwards. Skipping it lets the strength-0.95 anchor
  keyframes erode over the schedule, and those anchors are the only thing
  pinning adjacent tiles onto the same content.
- Velocity is converted to x0 with each token's own noise level, not the scalar
  schedule sigma: a token held at strength s sits at (1 - s) * sigma.
- Each tile draws its ancestral noise from a generator seeded
  seed + 1000 * round + tile, kept separate from the main generator so the
  draws do not consume state the next tile's initial noising reads.
- Two tiles invent the slot that falls in the later one's dropped lead-in. The
  stitch keeps the earlier tile's frames there, so the earlier tile's copy is
  the one the canvas holds, and the one the next round must anchor on.

* Split the DFR pipeline into composable stages

Addresses the review on #14567: use the same compose pattern as the other LTX
two-stage pipelines, get ancestral Euler from an existing scheduler, and put the
temporal rounds in their own pipeline so the schedule is not switched mid-call.

`LTX2DFRPipeline.__call__` is now one denoise pass at `height` x `width`. Callers
compose stage 1, `LTX2LatentUpsamplePipeline`, stage 2 and each temporal round,
and a documented recipe is the copy-paste 1080p path. The recipe knobs
(`spatial_upscalings`, `temporal_upscalings`, `detailing_lora_adapter_name`) and
the required upsampler components are gone; `height`/`width` are this pass, not
the final output.

`ancestral_euler_step` is replaced by `LTXEulerAncestralRFScheduler.step` plus a
re-application of the conditioning blend, which ancestral noise would otherwise
erode on the strength-0.95 seam anchors. The new `LTX2DFRTemporalRefinePipeline`
owns that scheduler and one round; stage 1, stage 2 and the epilogue stay on
`FlowMatchEulerDiscreteScheduler`. It refuses any other scheduler rather than
silently taking a deterministic step and returning a softer canvas.

Pack/unpack, `prepare_latents`, `denoise` and `encode_conditions` move to
`LTX2DFRCoreMixin` so neither pipeline subclasses the other. Public latents are
raw on both sides of every boundary, `output_type="latent"` returns the untrimmed
canvas so a slot on the pad is not dropped, and `trim_canvas` does the trim
before decode. `LTX2DFRPipelineOutput` carries `keyframes` and
`keyframe_positions`, which cannot be re-derived after a round.

Verified against the pre-split implementation: bit-exact on dummy components in
fp32 and bf16, with and without the IC-LoRA reference, over one and two rounds;
and within one bf16 ulp on the real checkpoint, where the only difference is that
the split normalizes upsampled latents in fp32 rather than bf16.

Also in this pass:

- `__call__` takes `video_tiles` (the `epilogue_tiles` layout) instead of a
  resolved token plan. Resolving one needs the RoPE coordinates that only exist
  once `prepare_latents` has run, so a caller could not build the plan at all.
- `rebuild_epilogue_keyframes` is public and takes and returns raw latents. The
  composed epilogue needs it, so it was public API in practice while named
  private, and its normalized return forced callers into `_denormalize_latents`.
- Drop prompt enhancement and `num_videos_per_prompt` from the temporal pipeline.
  Enhancement belongs to stage 1 -- re-running it would denoise the canvas under
  a different prompt than the one that generated it -- and the batch is set by
  the incoming latent canvas, so `num_videos_per_prompt > 1` only ever raised.
- Fix the docs recipe: `requested_frames` counted latent frames where
  `trim_canvas` wants pixel frames, truncating a 241-frame render to 25; the
  three pipelines share components, so place them together instead of offloading
  one and leaving `temporal_latent_upsampler` off the device; and the detailing
  IC-LoRA is applied at 0.5, the strength the reference hardcodes.

- Pass `crf=0` on the conditions in the refine-round test. The default CRF sends
  the image through H.264 re-compression, which needs PyAV, so the test failed on
  any environment without it while testing nothing about re-compression.

* Drop LTX2DFRCoreMixin in favor of # Copied from

Each DFR pipeline now owns pack/unpack, prepare_latents, and denoise so the
classes stay self-contained. Shared helpers copy from LTX2Pipeline /
LTX2ConditionPipeline, and DFR-specific methods copy from LTX2DFRPipeline.
dfr_core.py keeps only the constants and canvas helpers.

* inline _finalize_output

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* remove dfr_core.py

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* make return_dict=False return a tuple of 4, consistent with diffusers convention; update docs and pipeline output accordingly

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* small refactors to the ltx2 dfr testing suite

* save

* remove dfr_dummies.py.

* remove tests/pipelines/ltx2/test_ltx2_dfr_layout.py

---------

Co-authored-by: aartyomov <aartyomov@lightricks.com>
Co-authored-by: dg845 <58458699+dg845@users.noreply.github.com>
Co-authored-by: YiYi Xu <yixu310@gmail.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
2026-09-01 09:17:10 +05:30
2026-08-27 10:12:56 +05:30
2022-09-19 21:58:41 +02:00
2026-06-15 16:20:28 -10:00
2026-06-15 16:20:28 -10:00
2026-06-15 16:20:28 -10:00
2022-10-12 13:22:51 +02:00
2026-08-20 08:18:52 -07:00



GitHub GitHub release GitHub release Contributor Covenant X account

πŸ€— Diffusers is the go-to library for state-of-the-art pretrained diffusion models for generating images, audio, and even 3D structures of molecules. Whether you're looking for a simple inference solution or training your own diffusion models, πŸ€— Diffusers is a modular toolbox that supports both. Our library is designed with a focus on usability over performance, simple over easy, and customizability over abstractions.

πŸ€— Diffusers offers three core components:

  • State-of-the-art diffusion pipelines that can be run in inference with just a few lines of code.
  • Interchangeable noise schedulers for different diffusion speeds and output quality.
  • Pretrained models that can be used as building blocks, and combined with schedulers, for creating your own end-to-end diffusion systems.

Installation

We recommend installing πŸ€— Diffusers in a virtual environment from PyPI or Conda. For more details about installing PyTorch, please refer to their official documentation.

PyTorch

With pip (official package):

pip install --upgrade diffusers[torch]

With conda (maintained by the community):

conda install -c conda-forge diffusers

Apple Silicon (M1/M2) support

Please refer to the How to use Stable Diffusion in Apple Silicon guide.

Quickstart

Generating outputs is super easy with πŸ€— Diffusers. To generate an image from text, use the from_pretrained method to load any pretrained diffusion model (browse the Hub for 30,000+ checkpoints):

from diffusers import DiffusionPipeline
import torch

pipeline = DiffusionPipeline.from_pretrained("stable-diffusion-v1-5/stable-diffusion-v1-5", dtype=torch.float16)
pipeline.to("cuda")
pipeline("An image of a squirrel in Picasso style").images[0]

You can also dig into the models and schedulers toolbox to build your own diffusion system:

from diffusers import DDPMScheduler, UNet2DModel
from PIL import Image
import torch

scheduler = DDPMScheduler.from_pretrained("google/ddpm-cat-256")
model = UNet2DModel.from_pretrained("google/ddpm-cat-256").to("cuda")
scheduler.set_timesteps(50)

sample_size = model.config.sample_size
noise = torch.randn((1, 3, sample_size, sample_size), device="cuda")
input = noise

for t in scheduler.timesteps:
    with torch.no_grad():
        noisy_residual = model(input, t).sample
        prev_noisy_sample = scheduler.step(noisy_residual, t, input).prev_sample
        input = prev_noisy_sample

image = (input / 2 + 0.5).clamp(0, 1)
image = image.cpu().permute(0, 2, 3, 1).numpy()[0]
image = Image.fromarray((image * 255).round().astype("uint8"))
image

Check out the Quickstart to launch your diffusion journey today!

How to navigate the documentation

Documentation What can I learn?
Quickstart A basic crash course for loading pipelines, generating outputs, and applying common inference optimizations.
Loading Guides for how to load and configure all the components (pipelines, models, and schedulers) of the library, as well as how to use different schedulers.
Modular Diffusers Build flexible diffusion systems from modular pipeline components.
Optimization Guides for how to optimize your diffusion model to run faster and consume less memory.
Training Guides for how to train a diffusion model for different tasks with different training techniques.

Contribution

We ❀️ contributions from the open-source community! If you want to contribute to this library, please check out our Contribution guide. If you are using an AI agent, please point it at the project conventions in .ai/ first (install them as a plugin with claude plugin marketplace add huggingface/diffusers, or a skill at a time with diffusers-cli skills add <name>) β€” see Coding with AI agents. You can look out for issues you'd like to tackle to contribute to the library.

Also, say πŸ‘‹ in our public Discord channel Join us on Discord. We discuss the hottest trends about diffusion models, help each other with contributions, personal projects or just hang out β˜•.

Task Pipeline πŸ€— Hub
Unconditional Image Generation DDPM google/ddpm-ema-church-256
Text-to-Image Stable Diffusion Text-to-Image stable-diffusion-v1-5/stable-diffusion-v1-5
Text-to-Image unCLIP kakaobrain/karlo-v1-alpha
Text-to-Image DeepFloyd IF DeepFloyd/IF-I-XL-v1.0
Text-to-Image Kandinsky kandinsky-community/kandinsky-2-2-decoder
Text-guided Image-to-Image ControlNet lllyasviel/sd-controlnet-canny
Text-guided Image-to-Image InstructPix2Pix timbrooks/instruct-pix2pix
Text-guided Image-to-Image Stable Diffusion Image-to-Image stable-diffusion-v1-5/stable-diffusion-v1-5
Text-guided Image Inpainting Stable Diffusion Inpainting stable-diffusion-v1-5/stable-diffusion-inpainting
Image Variation Stable Diffusion Image Variation lambdalabs/sd-image-variations-diffusers
Super Resolution Stable Diffusion Upscale stabilityai/stable-diffusion-x4-upscaler
Super Resolution Stable Diffusion Latent Upscale stabilityai/sd-x2-latent-upscaler

Thank you for using us ❀️.

Credits

This library concretizes previous work by many different authors and would not have been possible without their great research and implementations. We'd like to thank, in particular, the following implementations which have helped us in our development and without which the API could not have been as polished today:

  • @CompVis' latent diffusion models library, available here
  • @hojonathanho original DDPM implementation, available here as well as the extremely useful translation into PyTorch by @pesser, available here
  • @ermongroup's DDIM implementation, available here
  • @yang-song's Score-VE and Score-VP implementations, available here

We also want to thank @heejkoo for the very helpful overview of papers, code and resources on diffusion models, available here as well as @crowsonkb and @rromb for useful discussions and insights.

Citation

@misc{von-platen-etal-2022-diffusers,
  author = {Patrick von Platen and Suraj Patil and Anton Lozhkov and Pedro Cuenca and Nathan Lambert and Kashif Rasul and Mishig Davaadorj and Dhruv Nair and Sayak Paul and William Berman and Yiyi Xu and Steven Liu and Thomas Wolf},
  title = {Diffusers: State-of-the-art diffusion models},
  year = {2022},
  publisher = {GitHub},
  journal = {GitHub repository},
  howpublished = {\url{https://github.com/huggingface/diffusers}}
}
Description
πŸ€— Diffusers: соврСмСнныС Π΄ΠΈΡ„Ρ„ΡƒΠ·ΠΈΠΎΠ½Π½Ρ‹Π΅ ΠΌΠΎΠ΄Π΅Π»ΠΈ для Π³Π΅Π½Π΅Ρ€Π°Ρ†ΠΈΠΈ ΠΈΠ·ΠΎΠ±Ρ€Π°ΠΆΠ΅Π½ΠΈΠΉ, Π²ΠΈΠ΄Π΅ΠΎ ΠΈ Π°ΡƒΠ΄ΠΈΠΎ Π² PyTorch.
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