feat(VideoEncoderConfig init): making VideoEncoderConfig more robust and adaptable to multiple backends

src/lerobot/datasets/__init__.py

@@ -41,8 +41,8 @@ from .lerobot_dataset import LeRobotDataset
 from .multi_dataset import MultiLeRobotDataset
 from .pipeline_features import aggregate_pipeline_dataset_features, create_initial_features
 from .pyav_utils import (
-    check_config_against_bundled_ffmpeg,
+    check_video_encoder_config_pyav,
-    detect_available_encoders,
+    detect_available_encoders_pyav,
     get_codec,
 )
 from .sampler import EpisodeAwareSampler
@@ -74,12 +74,12 @@ __all__ = [
     "aggregate_datasets",
     "aggregate_pipeline_dataset_features",
     "aggregate_stats",
-    "check_config_against_bundled_ffmpeg",
+    "check_video_encoder_config_pyav",
     "convert_image_to_video_dataset",
     "create_initial_features",
     "create_lerobot_dataset_card",
     "delete_episodes",
-    "detect_available_encoders",
+    "detect_available_encoders_pyav",
     "get_codec",
     "get_feature_stats",
     "load_episodes",

src/lerobot/datasets/pyav_utils.py

@@ -74,31 +74,18 @@ def _get_codec_video_formats(vcodec: str) -> tuple[str, ...]:
     return tuple(fmt.name for fmt in (codec.video_formats or []))
 
 
-@functools.cache
+def detect_available_encoders_pyav(encoders: list[str] | str) -> list[str]:
-def _all_video_encoders() -> tuple[str, ...]:
-    """Every video encoder PyAV exposes in the local FFmpeg build, sorted by name."""
-    result: list[str] = []
-    for name in sorted(av.codecs_available):
-        codec = get_codec(name)
-        if codec is not None and codec.type == "video":
-            result.append(name)
-    return tuple(result)
-
-
-def detect_available_encoders(encoders: list[str] | str | None = None) -> list[str]:
     """Return the subset of *encoders* available as video encoders in the local FFmpeg build.
 
-    ``None`` returns every video encoder PyAV exposes; a single ``str`` is probed as a list of one.
+    Each name is probed directly via :func:`get_codec`; input order is preserved.
     """
-    if encoders is None:
-        return list(_all_video_encoders())
     if isinstance(encoders, str):
         encoders = [encoders]
 
-    video_encoders = set(_all_video_encoders())
+    available: list[str] = []
-    available = []
     for name in encoders:
-        if name in video_encoders:
+        codec = get_codec(name)
+        if codec is not None and codec.type == "video":
             available.append(name)
         else:
             logger.debug("encoder '%s' not available as video encoder", name)
@@ -242,7 +229,7 @@ def _check_extra_options(
         _validate_extra_option(vcodec, key, value, opt)
 
 
-def check_config_against_bundled_ffmpeg(config: VideoEncoderConfig) -> None:
+def check_video_encoder_config_pyav(config: VideoEncoderConfig) -> None:
     """Verify *config* is compatible with the bundled FFmpeg build.
 
     Checks pixel format, tuning-field availability, value range/choices for

src/lerobot/datasets/video_utils.py

@@ -38,8 +38,8 @@ from datasets.features.features import register_feature
 from PIL import Image
 
 from lerobot.datasets.pyav_utils import (
-    check_config_against_bundled_ffmpeg,
+    check_video_encoder_config_pyav,
-    detect_available_encoders,
+    detect_available_encoders_pyav,
 )
 from lerobot.utils.import_utils import get_safe_default_video_backend
 
@@ -93,13 +93,56 @@ class VideoEncoderConfig:
     extra_options: dict[str, Any] = field(default_factory=dict)
 
     def __post_init__(self) -> None:
-        self.vcodec = resolve_vcodec(self.vcodec)
+        self.resolve_vcodec()
 
         # Empty-constructor ergonomics: ``VideoEncoderConfig()`` must "just work".
         if self.preset is None and self.vcodec == "libsvtav1":
             self.preset = LIBSVTAV1_DEFAULT_PRESET
 
-        check_config_against_bundled_ffmpeg(self)
+        self.validate()
+
+
+    def detect_available_encoders(self, encoders: list[str] | str) -> list[str]:
+        """Detect available encoders based on the video backend."""
+        if self.video_backend == "pyav":
+            return detect_available_encoders_pyav(encoders)
+        else:
+            return []
+
+
+    def validate(self) -> None:
+        """Validate the video encoder config."""
+        if self.video_backend == "pyav":
+            check_video_encoder_config_pyav(self)
+
+
+    def resolve_vcodec(self) -> None:
+        """Validate vcodec and resolve 'auto' to best available HW encoder, fallback to libsvtav1.
+
+        Any explicitly-requested codec that isn't in the local FFmpeg build is
+        also silently rewritten to ``libsvtav1`` so encoding never hard-fails on
+        a host missing the requested encoder.
+        """
+        if self.vcodec not in VALID_VIDEO_CODECS:
+            raise ValueError(
+                f"Invalid vcodec '{self.vcodec}'. Must be one of: {sorted(VALID_VIDEO_CODECS)}"
+            )
+        if self.vcodec == "auto":
+            available = self.detect_available_encoders(HW_ENCODERS)
+            for encoder in HW_ENCODERS:
+                if encoder in available:
+                    logger.info(f"Auto-selected video codec: {encoder}")
+                    self.vcodec = encoder
+                    return
+            logger.info("No hardware encoder available, falling back to software encoder 'libsvtav1'")
+            self.vcodec = "libsvtav1"
+
+        if self.detect_available_encoders(self.vcodec):
+            logger.info(f"Using video codec: {self.vcodec}")
+            self.vcodec = self.vcodec
+            return
+        raise ValueError(f"Unsupported video codec: {self.vcodec} with video backend {self.video_backend}")
+
 
     def get_codec_options(self, encoder_threads: int | None = None) -> dict[str, str]:
         """Build codec-specific FFmpeg options from the tuning fields.
@@ -186,24 +229,6 @@ def _get_codec_options(
     return opts
 
 
-def resolve_vcodec(vcodec: str) -> str:
-    """Validate vcodec and resolve 'auto' to best available HW encoder, fallback to libsvtav1."""
-    if vcodec not in VALID_VIDEO_CODECS:
-        raise ValueError(f"Invalid vcodec '{vcodec}'. Must be one of: {sorted(VALID_VIDEO_CODECS)}")
-    if vcodec != "auto" and detect_available_encoders(vcodec) != []:
-        logger.info(f"Using video codec: {vcodec}")
-        return vcodec
-    elif vcodec == "auto":
-        available = detect_available_encoders()
-        for encoder in HW_ENCODERS:
-            if encoder in available:
-                logger.info(f"Auto-selected video codec: {encoder}")
-                return encoder
-    else:
-        logger.info("No hardware encoder available, falling back to software encoder 'libsvtav1'")
-        return "libsvtav1"
-
-
 def decode_video_frames(
     video_path: Path | str,
     timestamps: list[float],