[feat] Migrate SD35 SamplingParam subclass to profile-based defaults

Replace SD35SamplingParam subclass with a profile-based configuration
approach. This introduces the PipelineProfile registry infrastructure
and migrates SD35 as the first model to use it, enabling a cleaner
separation between model defaults and the base SamplingParam class.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

fastvideo/configs/sample/base.py

@@ -103,17 +103,49 @@ class SamplingParam:
         self.__post_init__()
 
     @classmethod
-    def from_pretrained(cls, model_path: str) -> "SamplingParam":
-        from fastvideo.registry import get_sampling_param_cls_for_name
-        sampling_cls = get_sampling_param_cls_for_name(model_path)
-        if sampling_cls is not None:
-            sampling_param: SamplingParam = sampling_cls()
-        else:
-            logger.warning("Couldn't find an optimal sampling param for %s. Using the default sampling param.",
-                           model_path)
-            sampling_param = cls()
+    def _from_profile(
+        cls,
+        profile_name: str,
+    ) -> "SamplingParam":
+        """Create a ``SamplingParam`` with profile defaults applied.
 
-        return sampling_param
+        Looks up *profile_name* in the central profile registry,
+        creates a base ``SamplingParam()``, then delegates to
+        :meth:`update` so that ``__post_init__`` is called and
+        derived fields stay consistent.
+        """
+        from fastvideo.configs.sample.profiles import get_profile
+
+        profile = get_profile(profile_name)
+        if profile is None:
+            raise ValueError(f"Unknown profile: {profile_name}")
+        instance = cls()
+        instance.update(profile.defaults)
+        return instance
+
+    @classmethod
+    def from_pretrained(cls, model_path: str) -> "SamplingParam":
+        from fastvideo.registry import _get_config_info
+
+        config_info = _get_config_info(model_path, raise_on_missing=False)
+
+        if config_info is None:
+            logger.warning(
+                "Couldn't find an optimal sampling param "
+                "for %s. Using the default sampling param.",
+                model_path,
+            )
+            return cls()
+
+        # Profile-based path (preferred for new migrations).
+        if config_info.default_profile is not None:
+            return cls._from_profile(config_info.default_profile)
+
+        # Legacy path: use the registered subclass directly.
+        if config_info.sampling_param_cls is not None:
+            return config_info.sampling_param_cls()
+
+        return cls()
 
     @staticmethod
     def add_cli_args(parser: Any) -> Any:

fastvideo/configs/sample/profiles.py

@@ -0,0 +1,33 @@
+# SPDX-License-Identifier: Apache-2.0
+"""Pipeline profile registry for SamplingParam defaults.
+
+A *profile* is a named collection of default field values that can be
+applied to a base ``SamplingParam`` instance, replacing the need for
+model-specific ``SamplingParam`` subclasses.
+"""
+
+from __future__ import annotations
+
+from dataclasses import dataclass
+from typing import Any
+
+
+@dataclass
+class PipelineProfile:
+    """Named set of default overrides for SamplingParam."""
+
+    name: str
+    defaults: dict[str, Any]
+
+
+_PROFILE_REGISTRY: dict[str, PipelineProfile] = {}
+
+
+def register_profile(profile: PipelineProfile) -> None:
+    """Register a profile by name."""
+    _PROFILE_REGISTRY[profile.name] = profile
+
+
+def get_profile(name: str) -> PipelineProfile | None:
+    """Look up a profile by name."""
+    return _PROFILE_REGISTRY.get(name)

fastvideo/configs/sample/sd35.py

@@ -1,25 +1,5 @@
 # SPDX-License-Identifier: Apache-2.0
-
-from __future__ import annotations
-
-from dataclasses import dataclass
-
-from fastvideo.configs.sample.base import SamplingParam
-
-
-@dataclass
-class SD35SamplingParam(SamplingParam):
-
-    prompt: str | None = "a photo of a cat"
-    negative_prompt: str = ""
-
-    num_videos_per_prompt: int = 1
-    seed: int = 0
-
-    num_frames: int = 1
-    height: int = 512
-    width: int = 512
-    fps: int = 1
-
-    num_inference_steps: int = 28
-    guidance_scale: float = 6.0
+# SD35 sampling defaults have been migrated to profile-based
+# configuration.  See fastvideo/pipelines/basic/sd35/profiles.py
+# and use SamplingParam.from_pretrained(
+#     "stabilityai/stable-diffusion-3.5-medium") instead.

fastvideo/pipelines/basic/sd35/profiles.py

@@ -0,0 +1,28 @@
+# SPDX-License-Identifier: Apache-2.0
+"""Pipeline profiles for Stable Diffusion 3.5 model family.
+
+Each profile defines default sampling parameters that differ from the
+base ``SamplingParam`` defaults.
+"""
+
+from fastvideo.configs.sample.profiles import (
+    PipelineProfile,
+    register_profile,
+)
+
+SD35_MEDIUM = PipelineProfile(
+    name="sd35_medium",
+    defaults={
+        "negative_prompt": "",
+        "num_videos_per_prompt": 1,
+        "seed": 0,
+        "num_frames": 1,
+        "height": 512,
+        "width": 512,
+        "fps": 1,
+        "num_inference_steps": 28,
+        "guidance_scale": 6.0,
+    },
+)
+
+register_profile(SD35_MEDIUM)

fastvideo/registry.py

@@ -83,8 +83,6 @@ from fastvideo.configs.sample.wan import (
     WanT2V_14B_SamplingParam,
     WanT2V_1_3B_SamplingParam,
 )
-from fastvideo.configs.sample.sd35 import SD35SamplingParam
-
 from fastvideo.fastvideo_args import WorkloadType
 from fastvideo.logger import init_logger
 from fastvideo.utils import (maybe_download_model_index, verify_model_config_and_directory)
@@ -138,6 +136,7 @@ class ConfigInfo:
     sampling_param_cls: type[SamplingParam] | None
     pipeline_config_cls: type[PipelineConfig]
     workload_types: tuple[WorkloadType, ...]
+    default_profile: str | None = None
 
 
 # The central registry mapping a model name to its configuration information
@@ -156,6 +155,7 @@ def register_configs(
     workload_types: tuple[WorkloadType, ...],
     hf_model_paths: list[str] | None = None,
     model_detectors: list[Callable[[str], bool]] | None = None,
+    default_profile: str | None = None,
 ) -> None:
     """Register config classes for a model family.
 
@@ -168,6 +168,7 @@ def register_configs(
         sampling_param_cls=sampling_param_cls,
         pipeline_config_cls=pipeline_config_cls,
         workload_types=workload_types,
+        default_profile=default_profile,
     )
 
     if hf_model_paths:
@@ -624,8 +625,9 @@ def _register_configs() -> None:
     )
 
     # SD3.5
+    import fastvideo.pipelines.basic.sd35.profiles  # noqa: F401
     register_configs(
-        sampling_param_cls=SD35SamplingParam,
+        sampling_param_cls=None,
         pipeline_config_cls=SD35Config,
         workload_types=(WorkloadType.T2I, ),
         hf_model_paths=[
@@ -638,6 +640,7 @@ def _register_configs() -> None:
                 "stabilityai__stable-diffusion-3.5-medium",
             )),
         ],
+        default_profile="sd35_medium",
     )
 
 

fastvideo/tests/ssim/test_sd35_similarity.py

@@ -6,7 +6,7 @@ import os
 import pytest
 import torch
 
-from fastvideo.configs.sample.sd35 import SD35SamplingParam
+from fastvideo.configs.sample.base import SamplingParam
 from fastvideo.logger import init_logger
 from fastvideo.tests.ssim.inference_similarity_utils import (
     run_text_to_video_similarity_test,
@@ -60,7 +60,8 @@ SD35_PARAMS = {
     "neg_prompt": "lowres, blurry",
 }
 
-_SD35_FULL_QUALITY_DEFAULTS = SD35SamplingParam()
+_SD35_FULL_QUALITY_DEFAULTS = SamplingParam.from_pretrained(
+    "stabilityai/stable-diffusion-3.5-medium")
 SD35_FULL_QUALITY_PARAMS = {
     "num_gpus": 1,
     "model_path": SD35_MODEL_PATH,