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vllm-omni/examples/offline_inference/lance/end2end.py
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lishunyang12 7c934b6188 [Lance] Add Gradio demo and align inference with upstream
- Add ``examples/offline_inference/lance/gradio_demo.py`` — a unified 7-task UI
  (t2i / t2v / i2v / image_edit / video_edit / x2t_image / x2t_video) that
  loads ``Lance_3B`` and ``Lance_3B_Video`` on two GPUs so image and video
  tasks run concurrently.  Surfaces official Lance examples per task; aspect
  ratio is auto-snapped to one of upstream's 6 buckets from the input
  image/video.
- Fix x2t_image / x2t_video output format: route x2t_image through a new
  ``_forward_x2t_image`` handler (was falling through to the img2img path
  and emitting garbage), build the chat prefill in three segments
  (prefix → ViT → suffix) so the ``<|im_end|>`` markers line up with
  upstream's template, and start generation from a newline token instead of
  ``<|im_start|>`` so the assistant turn doesn't close itself with an
  immediate EOS.  Add a ``system_prompt`` override to ``render_lance_prompt``
  so per-example QA instructions surface ("Look at the image carefully and
  answer the question.") instead of the caption-style default.
- ``_forward_image_edit``: also stash the PIL image into ``custom_output``
  so callers reading ``outputs[0].output`` *or* ``custom_output["image"]``
  both work — the orchestrator IPC strips the bare ``output`` field across
  process boundaries.
- ``pipeline_registry.py``, ``model_executor/models/lance/*``, registry
  cleanup: remove the dead Lance-specific autoregressive shim
  (``lance.py``) and its stage-input processor; the diffusion pipeline owns
  the full flow now.
- Aspect-ratio buckets aligned with upstream's ``BucketResize`` (6 ratios:
  21:9 / 16:9 / 4:3 / 1:1 / 3:4 / 9:16, sized for ``resolution_vae`` ∈
  {480, 640, 768}).  3:2 / 2:3 dropped — upstream snaps those to 4:3 / 3:4.
- Gradio defaults match upstream's official scripts (cfg_text_scale=4.0,
  validation_num_timesteps=30, validation_timestep_shift=3.5, seed=42); only
  the demo *duration* is intentionally shorter than upstream's 121-frame
  default to keep the UI snappy (user can extend to 10s via slider for
  byte-identical reproduction).

Signed-off-by: lishunyang12 <lishunyang12@163.com>

Signed-off-by: WeiQing Chen <david6666666@users.noreply.github.com>
2026-05-31 11:40:40 +00:00

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# SPDX-License-Identifier: Apache-2.0
# SPDX-FileCopyrightText: Copyright contributors to the vLLM project
"""Lance-3B offline inference (single-stage).
Lance is BAGEL-lineage; this example covers the single-stage paths wired in
this PR:
text2img — image generation from text
img2text — image understanding (caption / VQA)
Examples:
python examples/offline_inference/lance/end2end.py \
--model bytedance-research/Lance \
--prompts "a corgi astronaut on the moon, cinematic" \
--output ./out
python examples/offline_inference/lance/end2end.py \
--model bytedance-research/Lance --modality img2text \
--image-path /path/to/photo.jpg \
--prompts "Describe this image in detail."
"""
import argparse
import os
def parse_args():
p = argparse.ArgumentParser()
p.add_argument("--model", default="bytedance-research/Lance", help="HF repo or local path.")
p.add_argument("--prompts", nargs="+", default=None, help="Input text prompts.")
p.add_argument("--txt-prompts", type=str, default=None, help="File with one prompt per line.")
p.add_argument(
"--modality",
default="text2img",
choices=["text2img", "img2text", "text2video", "video2text", "img2img", "video2video", "image2video"],
help="Lance single-stage modality.",
)
p.add_argument("--image-path", type=str, default=None, help="Input image for img2text.")
p.add_argument("--video-path", type=str, default=None, help="Input video file for video2text.")
p.add_argument("--num-frames", type=int, default=25, help="Number of RGB frames for text2video (max 121).")
p.add_argument("--video-height", type=int, default=480, help="Video frame height.")
p.add_argument("--video-width", type=int, default=768, help="Video frame width.")
p.add_argument("--height", type=int, default=None, help="Image height (t2i). Default = max_hw (1024).")
p.add_argument("--width", type=int, default=None, help="Image width (t2i). Default = max_hw (1024).")
p.add_argument(
"--fps", type=int, default=12, help="Output video FPS when saving MP4 (matches upstream Lance's save_fps=12)."
)
p.add_argument("--output", type=str, default=".", help="Output directory.")
p.add_argument("--steps", type=int, default=30, help="Denoising steps (Lance default 30).")
p.add_argument("--cfg-text-scale", type=float, default=4.0, help="Text CFG scale (Lance default 4.0).")
p.add_argument("--timestep-shift", type=float, default=3.5, help="Flow-match timestep shift (Lance default 3.5).")
p.add_argument("--negative-prompt", type=str, default=None)
p.add_argument("--seed", type=int, default=42)
p.add_argument("--max-text-tokens", type=int, default=512, help="Max tokens for img2text generation.")
p.add_argument(
"--do-sample",
action="store_true",
default=True,
help="Sample (vs greedy) for x2t generation; greedy frequently emits an immediate EOS for Lance.",
)
p.add_argument("--no-sample", dest="do_sample", action="store_false", help="Disable sampling (greedy decoding).")
p.add_argument(
"--text-temperature",
type=float,
default=0.8,
help="Sampling temperature for x2t generation. Lance frequently emits an immediate EOS below ~0.7; 0.8 is a good default.",
)
p.add_argument(
"--system-prompt",
type=str,
default=None,
help=(
"Override the task system prompt (used by x2t_image / x2t_video for "
'per-example QA instructions like "Look at the image carefully and '
'answer the question."; without it x2t falls back to a '
"caption-style default and the model describes instead of answering)."
),
)
p.add_argument(
"--deploy-config",
type=str,
default="vllm_omni/deploy/lance.yaml",
help="Deploy YAML (single-stage Lance).",
)
from vllm_omni.engine.arg_utils import nullify_stage_engine_defaults
nullify_stage_engine_defaults(p)
return p.parse_args()
from vllm_omni.diffusion.models.lance.prompts import ( # noqa: E402
VIDEO_PAD,
VISION_END,
VISION_START,
render_lance_prompt,
)
# Visual block matching upstream Lance: <|vision_start|><|video_pad|><|vision_end|>
# (Lance's renderer uses ``<|video_pad|>`` even for image inputs by default.)
_VISION_BLOCK = f"{VISION_START}{VIDEO_PAD}{VISION_END}"
def _format_text2img_prompts(prompts):
return [{"prompt": render_lance_prompt("t2i", p), "modalities": ["image"]} for p in prompts]
def _format_text2video_prompts(prompts, num_frames, video_h, video_w):
extra = {"num_frames": num_frames, "video_height": video_h, "video_width": video_w}
return [{"prompt": render_lance_prompt("t2v", p), "modalities": ["video"], "extra_args": extra} for p in prompts]
def _format_image2video_prompts(prompts, image_path, num_frames, video_h, video_w):
"""Image-to-Video (no first-frame pin): image + text → long video.
Passes the input image via ``multi_modal_data.first_frame``. The pipeline
treats it as a 1-frame reference (VAE+ViT prefill) and generates a fresh
multi-frame video at the requested ``num_frames`` × ``video_h`` ×
``video_w`` shape.
"""
import os as _os
if not image_path or not _os.path.exists(image_path):
raise ValueError(f"image2video requires --image-path pointing to an existing file, got: {image_path}")
from PIL import Image as _Image
img = _Image.open(image_path).convert("RGB")
extra = {"num_frames": num_frames, "video_height": video_h, "video_width": video_w}
return [
{
"prompt": render_lance_prompt("i2v", p, vision_token=_VISION_BLOCK),
"multi_modal_data": {"first_frame": img},
"modalities": ["video"],
"extra_args": extra,
}
for p in prompts
]
def _format_img2img_prompts(prompts, image_path):
import os as _os
if not image_path or not _os.path.exists(image_path):
raise ValueError(f"img2img requires --image-path pointing to an existing file, got: {image_path}")
from PIL import Image as _Image
img = _Image.open(image_path).convert("RGB")
return [
{
"prompt": render_lance_prompt("image_edit", p, vision_token=_VISION_BLOCK),
"multi_modal_data": {"img2img": img},
"modalities": ["image"],
}
for p in prompts
]
def _format_video2video_prompts(prompts, video_path, num_frames, video_h, video_w):
import os as _os
if not video_path or not _os.path.exists(video_path):
raise ValueError(f"video2video requires --video-path pointing to an existing file, got: {video_path}")
extra = {"num_frames": num_frames, "video_height": video_h, "video_width": video_w}
return [
{
"prompt": render_lance_prompt("video_edit", p, vision_token=_VISION_BLOCK),
"multi_modal_data": {"video": video_path},
"modalities": ["video"],
"extra_args": extra,
}
for p in prompts
]
def _format_video2text_prompts(prompts, video_path, system_prompt=None):
import os as _os
if not video_path or not _os.path.exists(video_path):
raise ValueError(f"video2text requires --video-path pointing to an existing file, got: {video_path}")
import imageio.v3 as iio
video = iio.imread(video_path)
return [
{
"prompt": render_lance_prompt("x2t_video", p, vision_token=_VISION_BLOCK, system_prompt=system_prompt),
"multi_modal_data": {"video": video},
"modalities": ["text"],
}
for p in prompts
]
def _format_img2text_prompts(prompts, image_path, system_prompt=None):
from PIL import Image
if not image_path or not os.path.exists(image_path):
raise ValueError(f"img2text requires --image-path pointing to an existing file, got: {image_path}")
img = Image.open(image_path).convert("RGB")
return [
{
"prompt": render_lance_prompt("x2t_image", p, vision_token=_VISION_BLOCK, system_prompt=system_prompt),
"multi_modal_data": {"image": img},
"modalities": ["text"],
}
for p in prompts
]
def main():
args = parse_args()
os.makedirs(args.output, exist_ok=True)
if args.txt_prompts:
with open(args.txt_prompts, encoding="utf-8") as f:
prompts = [ln.strip() for ln in f if ln.strip()]
elif args.modality == "img2text":
prompts = args.prompts or ["Describe this image in detail."]
else:
prompts = args.prompts or ["A cute cat, studio lighting, 4k"]
from vllm_omni.entrypoints.omni import Omni
# Video modalities require the Lance_3B_Video checkpoint (3D
# latent_pos_embed shaped (126976, 2048)). Without it, vllm-omni silently
# loads Lance_3B (4096, 2048) — the image-only table — and any t_lat >= 1
# immediately indexes out of bounds. Rewrite the model path so
# LancePipeline._select_video_variant picks the video subfolder.
resolved_model = args.model
if args.modality in ("text2video", "video2video", "video2text", "image2video"):
if not str(resolved_model).rstrip("/").endswith("Lance_3B_Video"):
candidate = os.path.join(resolved_model, "Lance_3B_Video")
if os.path.isdir(candidate):
resolved_model = candidate
omni_kwargs = vars(args).copy()
omni_kwargs["deploy_config"] = args.deploy_config
omni_kwargs["model"] = resolved_model
omni = Omni(**omni_kwargs)
if args.modality == "img2text":
formatted = _format_img2text_prompts(prompts, args.image_path, system_prompt=args.system_prompt)
elif args.modality == "text2video":
formatted = _format_text2video_prompts(prompts, args.num_frames, args.video_height, args.video_width)
elif args.modality == "video2text":
formatted = _format_video2text_prompts(prompts, args.video_path, system_prompt=args.system_prompt)
elif args.modality == "img2img":
formatted = _format_img2img_prompts(prompts, args.image_path)
elif args.modality == "video2video":
formatted = _format_video2video_prompts(
prompts, args.video_path, args.num_frames, args.video_height, args.video_width
)
elif args.modality == "image2video":
formatted = _format_image2video_prompts(
prompts, args.image_path, args.num_frames, args.video_height, args.video_width
)
else:
formatted = _format_text2img_prompts(prompts)
params_list = omni.default_sampling_params_list
diffusion_params = params_list[0] # single-stage: one param set
diffusion_params.num_inference_steps = args.steps # type: ignore
if args.seed is not None:
diffusion_params.seed = args.seed # type: ignore
if args.height is not None:
diffusion_params.height = args.height # type: ignore
if args.width is not None:
diffusion_params.width = args.width # type: ignore
extra = getattr(diffusion_params, "extra_args", {}) or {}
extra["cfg_text_scale"] = args.cfg_text_scale
extra["timestep_shift"] = args.timestep_shift
if args.modality in ("img2text", "video2text"):
extra["max_think_tokens"] = args.max_text_tokens
extra["do_sample"] = args.do_sample
extra["text_temperature"] = args.text_temperature
if args.negative_prompt is not None:
extra["negative_prompt"] = args.negative_prompt
diffusion_params.extra_args = extra # type: ignore
outputs = list(omni.generate(prompts=formatted, sampling_params_list=params_list))
if args.modality in ("img2text", "video2text"):
for i, req_output in enumerate(outputs):
text = getattr(req_output, "output", None) or getattr(req_output, "text", None)
if text is None and hasattr(req_output, "custom_output"):
text = (req_output.custom_output or {}).get("text_output")
print(f"[Output {i}] {text}")
return
if args.modality in ("text2video", "video2video", "image2video"):
for i, req_output in enumerate(outputs):
custom = getattr(req_output, "custom_output", None) or {}
frames = custom.get("video_frames")
if not frames:
print(f"[Output {i}] no video frames returned")
continue
mp4_path = os.path.join(args.output, f"lance_{i}.mp4")
try:
import imageio.v3 as iio
import numpy as np
arr = np.stack([np.asarray(f) for f in frames], axis=0)
iio.imwrite(mp4_path, arr, fps=args.fps, codec="libx264", quality=8)
print(f"[Output {i}] Saved MP4 ({len(frames)} frames, {arr.shape[1]}x{arr.shape[2]}) to {mp4_path}")
except Exception as exc:
print(f"[Output {i}] MP4 encode failed ({exc!r}); writing per-frame ONGs instead")
frame_dir = os.path.join(args.output, f"lance_{i}_frames")
os.makedirs(frame_dir, exist_ok=True)
for j, frame in enumerate(frames):
frame.save(os.path.join(frame_dir, f"{j:04d}.png"))
print(f" → {frame_dir} ({len(frames)} frames)")
return
idx = 0
for req_output in outputs:
images = getattr(req_output, "images", None)
if not images:
continue
for j, img in enumerate(images):
path = os.path.join(args.output, f"lance_{idx}_{j}.png")
img.save(path)
print(f"[Output] Saved image to {path}")
idx += 1
if __name__ == "__main__":
main()