[diffusion] feat: add support for additional sampling parameters in video generation API (#15062)

Co-authored-by: Mick <mickjagger19@icloud.com>

python/sglang/multimodal_gen/configs/sample/sampling_params.py

@@ -123,6 +123,7 @@ class SamplingParams:
     # Denoising parameters
     num_inference_steps: int = None
     guidance_scale: float = None
+    guidance_scale_2: float = None
     guidance_rescale: float = 0.0
     boundary_ratio: float | None = None
 
@@ -494,6 +495,13 @@ class SamplingParams:
             default=SamplingParams.guidance_scale,
             help="Classifier-free guidance scale",
         )
+        parser.add_argument(
+            "--guidance-scale-2",
+            type=float,
+            default=SamplingParams.guidance_scale_2,
+            dest="guidance_scale_2",
+            help="Secondary guidance scale for dual-guidance models (e.g., Wan low-noise expert)",
+        )
         parser.add_argument(
             "--guidance-rescale",
             type=float,
@@ -589,7 +597,7 @@ class SamplingParams:
         attrs = sampling_params_fields & args_attrs
         args.height_not_provided = False
         args.width_not_provided = False
-        return {attr: getattr(args, attr) for attr in attrs}
+        return {attr: getattr(args, attr) for attr in attrs if hasattr(args, attr)}
 
     def output_file_path(self):
         return os.path.join(self.output_path, self.output_file_name)

python/sglang/multimodal_gen/runtime/entrypoints/openai/protocol.py

@@ -58,6 +58,10 @@ class VideoGenerationsRequest(BaseModel):
     num_frames: Optional[int] = None
     seed: Optional[int] = 1024
     generator_device: Optional[str] = "cuda"
+    num_inference_steps: Optional[int] = None
+    guidance_scale: Optional[float] = None
+    guidance_scale_2: Optional[float] = None
+    negative_prompt: Optional[str] = None
 
 
 class VideoListResponse(BaseModel):

python/sglang/multimodal_gen/runtime/entrypoints/openai/video_api.py

@@ -61,20 +61,31 @@ def _build_sampling_params_from_request(
         request.num_frames if request.num_frames is not None else derived_num_frames
     )
     server_args = get_global_server_args()
+    sampling_kwargs = {
+        "request_id": request_id,
+        "prompt": request.prompt,
+        "num_frames": num_frames,
+        "fps": fps,
+        "width": width,
+        "height": height,
+        "image_path": request.input_reference,
+        "save_output": True,
+        "output_file_name": request_id,
+        "seed": request.seed,
+        "generator_device": request.generator_device,
+    }
+    if request.num_inference_steps is not None:
+        sampling_kwargs["num_inference_steps"] = request.num_inference_steps
+    if request.guidance_scale is not None:
+        sampling_kwargs["guidance_scale"] = request.guidance_scale
+    if request.guidance_scale_2 is not None:
+        sampling_kwargs["guidance_scale_2"] = request.guidance_scale_2
+    if request.negative_prompt is not None:
+        sampling_kwargs["negative_prompt"] = request.negative_prompt
     sampling_params = SamplingParams.from_user_sampling_params_args(
         model_path=server_args.model_path,
-        request_id=request_id,
-        prompt=request.prompt,
-        num_frames=num_frames,
-        fps=fps,
-        width=width,
-        height=height,
-        image_path=request.input_reference,
-        save_output=True,
         server_args=server_args,
-        output_file_name=request_id,
-        seed=request.seed,
-        generator_device=request.generator_device,
+        **sampling_kwargs,
     )
 
     return sampling_params