test(new): adding new tests for encoding related features

tests/datasets/test_streaming_video_encoder.py

@@ -14,11 +14,10 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-"""Tests for streaming video encoding and hardware-accelerated encoding."""
+"""Tests for streaming video encoding."""
 
 import queue
 import threading
-from unittest.mock import patch
 
 import numpy as np
 import pytest
@@ -27,112 +26,20 @@ pytest.importorskip("av", reason="av is required (install lerobot[dataset])")
 
 import av  # noqa: E402
 
+from lerobot.datasets.pyav_utils import get_codec
 from lerobot.datasets.video_utils import (
-    VALID_VIDEO_CODECS,
     StreamingVideoEncoder,
+    VideoEncoderConfig,
     _CameraEncoderThread,
-    _get_codec_options,
-    detect_available_hw_encoders,
-    resolve_vcodec,
 )
 from lerobot.utils.constants import OBS_IMAGES
 
-# ─── _get_codec_options tests ───
+# Cross-codec validation tests only fire when the target codec is present
-
+# in the local FFmpeg build; on other platforms validate() is a no-op.
-
+_has_videotoolbox = get_codec("h264_videotoolbox") is not None
-class TestGetCodecOptions:
+_videotoolbox_only = pytest.mark.skipif(
-    def test_libsvtav1_defaults(self):
+    not _has_videotoolbox, reason="h264_videotoolbox not in local FFmpeg build"
-        opts = _get_codec_options("libsvtav1")
+)
-        assert opts["g"] == "2"
-        assert opts["crf"] == "30"
-        assert opts["preset"] == "12"
-
-    def test_libsvtav1_custom_preset(self):
-        opts = _get_codec_options("libsvtav1", preset=8)
-        assert opts["preset"] == "8"
-
-    def test_h264_options(self):
-        opts = _get_codec_options("h264", g=10, crf=23)
-        assert opts["g"] == "10"
-        assert opts["crf"] == "23"
-        assert "preset" not in opts
-
-    def test_videotoolbox_options(self):
-        opts = _get_codec_options("h264_videotoolbox", g=2, crf=30)
-        assert opts["g"] == "2"
-        # CRF 30 maps to quality = max(1, min(100, 100 - 30*2)) = 40
-        assert opts["q:v"] == "40"
-        assert "crf" not in opts
-
-    def test_nvenc_options(self):
-        opts = _get_codec_options("h264_nvenc", g=2, crf=25)
-        assert opts["rc"] == "constqp"
-        assert opts["qp"] == "25"
-        assert "crf" not in opts
-        # NVENC doesn't support g
-        assert "g" not in opts
-
-    def test_vaapi_options(self):
-        opts = _get_codec_options("h264_vaapi", crf=28)
-        assert opts["qp"] == "28"
-
-    def test_qsv_options(self):
-        opts = _get_codec_options("h264_qsv", crf=25)
-        assert opts["global_quality"] == "25"
-
-    def test_no_g_no_crf(self):
-        opts = _get_codec_options("h264", g=None, crf=None)
-        assert "g" not in opts
-        assert "crf" not in opts
-
-
-# ─── HW encoder detection tests ───
-
-
-class TestHWEncoderDetection:
-    def test_detect_available_hw_encoders_returns_list(self):
-        result = detect_available_hw_encoders()
-        assert isinstance(result, list)
-
-    def test_detect_available_hw_encoders_only_valid(self):
-        from lerobot.datasets.video_utils import HW_ENCODERS
-
-        result = detect_available_hw_encoders()
-        for encoder in result:
-            assert encoder in HW_ENCODERS
-
-    def test_resolve_vcodec_passthrough(self):
-        assert resolve_vcodec("libsvtav1") == "libsvtav1"
-        assert resolve_vcodec("h264") == "h264"
-
-    def test_resolve_vcodec_auto_fallback(self):
-        """When no HW encoders are available, auto should fall back to libsvtav1."""
-        with patch("lerobot.datasets.video_utils.detect_available_hw_encoders", return_value=[]):
-            assert resolve_vcodec("auto") == "libsvtav1"
-
-    def test_resolve_vcodec_auto_picks_hw(self):
-        """When a HW encoder is available, auto should pick it."""
-        with patch(
-            "lerobot.datasets.video_utils.detect_available_hw_encoders",
-            return_value=["h264_videotoolbox"],
-        ):
-            assert resolve_vcodec("auto") == "h264_videotoolbox"
-
-    def test_resolve_vcodec_auto_returns_valid(self):
-        """Test that resolve_vcodec('auto') returns a known valid codec."""
-        result = resolve_vcodec("auto")
-        assert result in VALID_VIDEO_CODECS
-
-    def test_hw_encoder_names_accepted_in_validation(self):
-        """Test that HW encoder names pass validation in VALID_VIDEO_CODECS."""
-        assert "auto" in VALID_VIDEO_CODECS
-        assert "h264_videotoolbox" in VALID_VIDEO_CODECS
-        assert "h264_nvenc" in VALID_VIDEO_CODECS
-
-    def test_resolve_vcodec_invalid_raises(self):
-        """Test that resolve_vcodec raises ValueError for invalid codecs."""
-        with pytest.raises(ValueError, match="Invalid vcodec"):
-            resolve_vcodec("not_a_real_codec")
 
 
 # ─── _CameraEncoderThread tests ───
@@ -150,14 +57,13 @@ class TestCameraEncoderThread:
         result_queue: queue.Queue = queue.Queue(maxsize=1)
         stop_event = threading.Event()
 
+        enc_cfg = VideoEncoderConfig(vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30, preset=13)
         encoder_thread = _CameraEncoderThread(
             video_path=video_path,
             fps=fps,
-            vcodec="libsvtav1",
+            vcodec=enc_cfg.vcodec,
-            pix_fmt="yuv420p",
+            pix_fmt=enc_cfg.pix_fmt,
-            g=2,
+            codec_options=enc_cfg.get_codec_options(),
-            crf=30,
-            preset=13,
             frame_queue=frame_queue,
             result_queue=result_queue,
             stop_event=stop_event,
@@ -202,14 +108,13 @@ class TestCameraEncoderThread:
         result_queue: queue.Queue = queue.Queue(maxsize=1)
         stop_event = threading.Event()
 
+        enc_cfg = VideoEncoderConfig(vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30, preset=13)
         encoder_thread = _CameraEncoderThread(
             video_path=video_path,
             fps=fps,
-            vcodec="libsvtav1",
+            vcodec=enc_cfg.vcodec,
-            pix_fmt="yuv420p",
+            pix_fmt=enc_cfg.pix_fmt,
-            g=2,
+            codec_options=enc_cfg.get_codec_options(),
-            crf=30,
-            preset=13,
             frame_queue=frame_queue,
             result_queue=result_queue,
             stop_event=stop_event,
@@ -237,14 +142,13 @@ class TestCameraEncoderThread:
         result_queue: queue.Queue = queue.Queue(maxsize=1)
         stop_event = threading.Event()
 
+        enc_cfg = VideoEncoderConfig(vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30, preset=13)
         encoder_thread = _CameraEncoderThread(
             video_path=video_path,
             fps=fps,
-            vcodec="libsvtav1",
+            vcodec=enc_cfg.vcodec,
-            pix_fmt="yuv420p",
+            pix_fmt=enc_cfg.pix_fmt,
-            g=2,
+            codec_options=enc_cfg.get_codec_options(),
-            crf=30,
-            preset=13,
             frame_queue=frame_queue,
             result_queue=result_queue,
             stop_event=stop_event,
@@ -266,11 +170,20 @@ class TestCameraEncoderThread:
 
 
 class TestStreamingVideoEncoder:
+    def _make_encoder_config(self, **kwargs):
+        """Helper to build a VideoEncoderConfig."""
+        return VideoEncoderConfig(**kwargs)
+
     def test_single_camera_episode(self, tmp_path):
         """Test encoding a single camera episode."""
-        encoder = StreamingVideoEncoder(fps=30, vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30, preset=13)
-
         video_keys = [f"{OBS_IMAGES}.laptop"]
+        encoder = StreamingVideoEncoder(
+            fps=30,
+            camera_encoder_config=self._make_encoder_config(
+                vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30, preset=13
+            ),
+        )
+
         encoder.start_episode(video_keys, tmp_path)
 
         num_frames = 20
@@ -295,9 +208,13 @@ class TestStreamingVideoEncoder:
 
     def test_multi_camera_episode(self, tmp_path):
         """Test encoding multiple cameras simultaneously."""
-        encoder = StreamingVideoEncoder(fps=30, vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30)
-
         video_keys = [f"{OBS_IMAGES}.laptop", f"{OBS_IMAGES}.phone"]
+        encoder = StreamingVideoEncoder(
+            fps=30,
+            camera_encoder_config=self._make_encoder_config(
+                vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30
+            ),
+        )
         encoder.start_episode(video_keys, tmp_path)
 
         num_frames = 15
@@ -319,8 +236,13 @@ class TestStreamingVideoEncoder:
 
     def test_sequential_episodes(self, tmp_path):
         """Test that multiple sequential episodes work correctly."""
-        encoder = StreamingVideoEncoder(fps=30, vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30)
         video_keys = [f"{OBS_IMAGES}.cam"]
+        encoder = StreamingVideoEncoder(
+            fps=30,
+            camera_encoder_config=self._make_encoder_config(
+                vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30
+            ),
+        )
 
         for ep in range(3):
             encoder.start_episode(video_keys, tmp_path)
@@ -342,8 +264,13 @@ class TestStreamingVideoEncoder:
 
     def test_cancel_episode(self, tmp_path):
         """Test that canceling an episode cleans up properly."""
-        encoder = StreamingVideoEncoder(fps=30, vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30)
         video_keys = [f"{OBS_IMAGES}.cam"]
+        encoder = StreamingVideoEncoder(
+            fps=30,
+            camera_encoder_config=self._make_encoder_config(
+                vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30
+            ),
+        )
 
         encoder.start_episode(video_keys, tmp_path)
 
@@ -365,28 +292,33 @@ class TestStreamingVideoEncoder:
 
     def test_feed_without_start_raises(self, tmp_path):
         """Test that feeding frames without starting an episode raises."""
-        encoder = StreamingVideoEncoder(fps=30, vcodec="libsvtav1", pix_fmt="yuv420p")
+        encoder = StreamingVideoEncoder(fps=30)
         with pytest.raises(RuntimeError, match="No active episode"):
             encoder.feed_frame("cam", np.zeros((64, 96, 3), dtype=np.uint8))
         encoder.close()
 
     def test_finish_without_start_raises(self, tmp_path):
         """Test that finishing without starting raises."""
-        encoder = StreamingVideoEncoder(fps=30, vcodec="libsvtav1", pix_fmt="yuv420p")
+        encoder = StreamingVideoEncoder(fps=30)
         with pytest.raises(RuntimeError, match="No active episode"):
             encoder.finish_episode()
         encoder.close()
 
     def test_close_is_idempotent(self, tmp_path):
         """Test that close() can be called multiple times safely."""
-        encoder = StreamingVideoEncoder(fps=30, vcodec="libsvtav1", pix_fmt="yuv420p")
+        encoder = StreamingVideoEncoder(fps=30)
         encoder.close()
         encoder.close()  # Should not raise
 
     def test_video_duration_matches_frame_count(self, tmp_path):
         """Test that encoded video duration matches num_frames / fps."""
-        encoder = StreamingVideoEncoder(fps=30, vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30, preset=13)
         video_keys = [f"{OBS_IMAGES}.cam"]
+        encoder = StreamingVideoEncoder(
+            fps=30,
+            camera_encoder_config=self._make_encoder_config(
+                vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30, preset=13
+            ),
+        )
         encoder.start_episode(video_keys, tmp_path)
 
         num_frames = 90  # 3 seconds at 30fps
@@ -417,9 +349,13 @@ class TestStreamingVideoEncoder:
 
     def test_multi_camera_start_episode_called_once(self, tmp_path):
         """Test that with multiple cameras, no frames are lost due to double start_episode."""
-        encoder = StreamingVideoEncoder(fps=30, vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30)
-
         video_keys = [f"{OBS_IMAGES}.cam1", f"{OBS_IMAGES}.cam2"]
+        encoder = StreamingVideoEncoder(
+            fps=30,
+            camera_encoder_config=self._make_encoder_config(
+                vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30
+            ),
+        )
         encoder.start_episode(video_keys, tmp_path)
 
         num_frames = 30
@@ -446,17 +382,24 @@ class TestStreamingVideoEncoder:
 
     def test_encoder_threads_passed_to_thread(self, tmp_path):
         """Test that encoder_threads is stored and passed through to encoder threads."""
-        encoder = StreamingVideoEncoder(
-            fps=30, vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30, encoder_threads=2
-        )
-        assert encoder.encoder_threads == 2
-
         video_keys = [f"{OBS_IMAGES}.cam"]
+        cfg = VideoEncoderConfig(
+            vcodec="libsvtav1",
+            pix_fmt="yuv420p",
+            g=2,
+            crf=30,
+        )
+        encoder = StreamingVideoEncoder(
+            fps=30,
+            camera_encoder_config=cfg,
+            encoder_threads=2,
+        )
+        assert encoder._encoder_threads == 2
         encoder.start_episode(video_keys, tmp_path)
 
-        # Verify the thread received the encoder_threads value
+        # Verify codec options include thread tuning for libsvtav1 (lp=…)
         thread = encoder._threads[f"{OBS_IMAGES}.cam"]
-        assert thread.encoder_threads == 2
+        assert "svtav1-params" in thread.codec_options or "threads" in thread.codec_options
 
         # Feed some frames and finish to ensure it works end-to-end
         num_frames = 10
@@ -478,16 +421,20 @@ class TestStreamingVideoEncoder:
 
     def test_encoder_threads_none_by_default(self, tmp_path):
         """Test that encoder_threads defaults to None (codec auto-detect)."""
-        encoder = StreamingVideoEncoder(fps=30, vcodec="libsvtav1", pix_fmt="yuv420p")
+        encoder = StreamingVideoEncoder(fps=30)
-        assert encoder.encoder_threads is None
+        assert encoder._encoder_threads is None
         encoder.close()
 
     def test_graceful_frame_dropping(self, tmp_path):
         """Test that full queue drops frames instead of crashing."""
-        encoder = StreamingVideoEncoder(
-            fps=30, vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30, preset=13, queue_maxsize=1
-        )
         video_keys = [f"{OBS_IMAGES}.cam"]
+        encoder = StreamingVideoEncoder(
+            fps=30,
+            camera_encoder_config=self._make_encoder_config(
+                vcodec="libsvtav1", pix_fmt="yuv420p", g=2, crf=30, preset=13
+            ),
+            queue_maxsize=1,
+        )
         encoder.start_episode(video_keys, tmp_path)
 
         # Feed many frames quickly - with queue_maxsize=1, some will be dropped

tests/datasets/test_video_encoding.py

@@ -0,0 +1,538 @@
+#!/usr/bin/env python
+
+# Copyright 2026 The HuggingFace Inc. team. All rights reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+"""Unit tests for ``lerobot.datasets.video_utils`` encoding functions and ``VideoEncoderConfig`` config class."""
+
+import json
+from pathlib import Path
+
+import numpy as np
+import pytest
+
+pytest.importorskip("av", reason="av is required (install lerobot[dataset])")
+
+import av  # noqa: E402
+
+from lerobot.datasets.image_writer import write_image
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
+from lerobot.datasets.pyav_utils import detect_available_encoders_pyav, get_codec
+from lerobot.datasets.utils import INFO_PATH
+from lerobot.datasets.video_utils import (
+    VALID_VIDEO_CODECS,
+    VideoEncoderConfig,
+    concatenate_video_files,
+    encode_video_frames,
+    get_video_info,
+)
+
+# Per-codec skip markers — validation tests only fire when the codec is available
+def _require_encoder(vcodec: str) -> pytest.MarkDecorator:
+    """Skip the test if ``vcodec`` is not available in the local FFmpeg build."""
+    return pytest.mark.skipif(
+        get_codec(vcodec) is None, reason=f"{vcodec!r} not in local FFmpeg build"
+    )
+
+
+require_libsvtav1 = _require_encoder("libsvtav1")
+require_h264 = _require_encoder("h264")
+require_videotoolbox = _require_encoder("h264_videotoolbox")
+require_nvenc = _require_encoder("h264_nvenc")
+require_vaapi = _require_encoder("h264_vaapi")
+require_qsv = _require_encoder("h264_qsv")
+
+
+# ─── VideoEncoderConfig / codec options ──────────────────────────────
+
+
+class TestCodecOptions:
+    @require_libsvtav1
+    def test_libsvtav1_defaults(self):
+        cfg = VideoEncoderConfig()
+        opts = cfg.get_codec_options()
+        assert opts["g"] == "2"
+        assert opts["crf"] == "30"
+        assert opts["preset"] == "12"
+
+    @require_libsvtav1
+    def test_libsvtav1_custom_preset(self):
+        cfg = VideoEncoderConfig(preset=8)
+        assert cfg.get_codec_options()["preset"] == "8"
+
+    @require_h264
+    def test_h264_options(self):
+        cfg = VideoEncoderConfig(vcodec="h264", g=10, crf=23, preset=None)
+        opts = cfg.get_codec_options()
+        assert opts["g"] == "10"
+        assert opts["crf"] == "23"
+        assert "preset" not in opts
+
+    @require_videotoolbox
+    def test_videotoolbox_options(self):
+        cfg = VideoEncoderConfig(vcodec="h264_videotoolbox", g=2, crf=30, preset=None)
+        opts = cfg.get_codec_options()
+        assert opts["g"] == "2"
+        assert opts["q:v"] == "40"
+        assert "crf" not in opts
+
+    @_require_encoder("h264_nvenc")
+    def test_nvenc_options(self):
+        cfg = VideoEncoderConfig(vcodec="h264_nvenc", g=2, crf=25, preset=None)
+        opts = cfg.get_codec_options()
+        assert opts["rc"] == "constqp"
+        assert opts["qp"] == "25"
+        assert "crf" not in opts
+        assert "g" not in opts
+
+    @_require_encoder("h264_vaapi")
+    def test_vaapi_options(self):
+        cfg = VideoEncoderConfig(vcodec="h264_vaapi", crf=28, preset=None)
+        assert cfg.get_codec_options()["qp"] == "28"
+
+    @_require_encoder("h264_qsv")
+    def test_qsv_options(self):
+        cfg = VideoEncoderConfig(vcodec="h264_qsv", crf=25, preset=None)
+        assert cfg.get_codec_options()["global_quality"] == "25"
+
+    @require_h264
+    def test_no_g_no_crf(self):
+        cfg = VideoEncoderConfig(vcodec="h264", g=None, crf=None, preset=None)
+        opts = cfg.get_codec_options()
+        assert "g" not in opts
+        assert "crf" not in opts
+
+    @require_libsvtav1
+    def test_encoder_threads_libsvtav1(self):
+        cfg = VideoEncoderConfig(fast_decode=0)
+        opts = cfg.get_codec_options(encoder_threads=4)
+        assert "lp=4" in opts.get("svtav1-params", "")
+
+    @require_h264
+    def test_encoder_threads_h264(self):
+        cfg = VideoEncoderConfig(vcodec="h264", preset=None)
+        assert cfg.get_codec_options(encoder_threads=2)["threads"] == "2"
+
+    @require_libsvtav1
+    def test_fast_decode_libsvtav1(self):
+        cfg = VideoEncoderConfig(fast_decode=1)
+        opts = cfg.get_codec_options()
+        assert "fast-decode=1" in opts.get("svtav1-params", "")
+
+    @require_h264
+    def test_fast_decode_h264(self):
+        cfg = VideoEncoderConfig(vcodec="h264", fast_decode=1, preset=None)
+        assert cfg.get_codec_options()["tune"] == "fastdecode"
+
+    @require_libsvtav1
+    def test_pix_fmt_unsupported_raises(self):
+        """Passing an unsupported pix_fmt is a hard error."""
+        with pytest.raises(ValueError, match="pix_fmt"):
+            VideoEncoderConfig(pix_fmt="yuv444p")  # libsvtav1 only supports yuv420p variants
+
+    @require_libsvtav1
+    @require_h264
+    def test_preset_default_behaviour(self):
+        """Empty constructor picks preset=12 (libsvtav1 path); other codecs stay None."""
+        assert VideoEncoderConfig().preset == 12
+        assert VideoEncoderConfig(vcodec="libsvtav1").preset == 12
+        assert VideoEncoderConfig(vcodec="h264").preset is None
+        assert VideoEncoderConfig(vcodec="h264", preset=None).preset is None
+
+    @require_h264
+    def test_preset_string_on_h264(self):
+        """h264 accepts string presets and forwards them to FFmpeg."""
+        cfg = VideoEncoderConfig(vcodec="h264", preset="slow")
+        assert cfg.get_codec_options()["preset"] == "slow"
+
+    @require_videotoolbox
+    def test_preset_on_videotoolbox_raises(self):
+        """videotoolbox has no preset option at all."""
+        with pytest.raises(ValueError, match="preset"):
+            VideoEncoderConfig(vcodec="h264_videotoolbox", preset="slow")
+
+    @require_libsvtav1
+    def test_libsvtav1_preset_out_of_range_raises(self):
+        """libsvtav1 preset must sit in [-2, 13] as exposed by PyAV."""
+        with pytest.raises(ValueError, match="out of range"):
+            VideoEncoderConfig(vcodec="libsvtav1", preset=100)
+        with pytest.raises(ValueError, match="out of range"):
+            VideoEncoderConfig(vcodec="libsvtav1", preset=-3)
+
+    @require_libsvtav1
+    def test_libsvtav1_crf_out_of_range_raises(self):
+        """libsvtav1 crf must sit in [0, 63]."""
+        with pytest.raises(ValueError, match="crf.*out of range"):
+            VideoEncoderConfig(vcodec="libsvtav1", crf=64)
+
+    @require_h264
+    def test_h264_crf_accepts_float_and_int(self):
+        """x264 exposes crf as a FLOAT option, so both int and float are accepted."""
+        assert VideoEncoderConfig(vcodec="h264", crf=23).get_codec_options()["crf"] == "23"
+        assert VideoEncoderConfig(vcodec="h264", crf=23.5).get_codec_options()["crf"] == "23.5"
+
+    @require_libsvtav1
+    def test_validate_is_rerunnable(self):
+        """After mutating a field, validate() re-checks and surfaces new issues."""
+        cfg = VideoEncoderConfig(vcodec="libsvtav1")
+        cfg.preset = 100  # now out of range
+        with pytest.raises(ValueError, match="out of range"):
+            cfg.validate()
+
+    @require_videotoolbox
+    def test_fast_decode_on_videotoolbox_raises(self):
+        """videotoolbox has no `tune` option; fast_decode must not be silently dropped."""
+        with pytest.raises(ValueError, match="fast_decode"):
+            VideoEncoderConfig(vcodec="h264_videotoolbox", preset=None, fast_decode=1)
+
+
+class TestExtraOptions:
+    @require_libsvtav1
+    def test_default_is_empty_dict(self):
+        cfg = VideoEncoderConfig()
+        assert cfg.extra_options == {}
+
+    @require_libsvtav1
+    def test_unknown_key_passes_through(self):
+        """Keys not published as AVOptions are forwarded to FFmpeg."""
+        cfg = VideoEncoderConfig(extra_options={"totally_made_up_option": "value"})
+        assert cfg.extra_options == {"totally_made_up_option": "value"}
+
+    @require_libsvtav1
+    def test_numeric_value_in_range_ok(self):
+        """libsvtav1 exposes ``qp`` as INT in [0, 63]."""
+        cfg = VideoEncoderConfig(extra_options={"qp": 30})
+        assert cfg.extra_options == {"qp": 30}
+
+    @require_libsvtav1
+    def test_numeric_out_of_range_raises(self):
+        with pytest.raises(ValueError, match=r"extra_options\['qp'\].*out of range"):
+            VideoEncoderConfig(extra_options={"qp": 999})
+
+    @require_libsvtav1
+    def test_numeric_string_accepted_in_range(self):
+        """Numeric strings are accepted for numeric options (mirrors FFmpeg)."""
+        cfg = VideoEncoderConfig(extra_options={"qp": "18"})
+        assert cfg.extra_options == {"qp": "18"}
+
+    @require_libsvtav1
+    def test_numeric_string_out_of_range_raises(self):
+        with pytest.raises(ValueError, match=r"extra_options\['qp'\].*out of range"):
+            VideoEncoderConfig(extra_options={"qp": "999"})
+
+    @require_libsvtav1
+    def test_non_numeric_string_on_numeric_option_raises(self):
+        with pytest.raises(ValueError, match=r"extra_options\['qp'\].*not numeric"):
+            VideoEncoderConfig(extra_options={"qp": "medium"})
+
+    @require_libsvtav1
+    def test_bool_on_numeric_option_raises(self):
+        """``bool`` is explicitly rejected for numeric options."""
+        with pytest.raises(ValueError, match=r"extra_options\['qp'\].*not numeric"):
+            VideoEncoderConfig(extra_options={"qp": True})
+
+    @require_h264
+    def test_string_option_passes_through_unchecked(self):
+        """String-typed AVOptions are NOT enum-checked (too many accept freeform)."""
+        cfg = VideoEncoderConfig(vcodec="h264", preset=None, extra_options={"tune": "some-future-tune"})
+        assert cfg.extra_options == {"tune": "some-future-tune"}
+
+    @require_libsvtav1
+    def test_merged_into_codec_options_and_stringified(self):
+        """extra_options are merged into get_codec_options() as strings."""
+        cfg = VideoEncoderConfig(extra_options={"qp": 20})
+        opts = cfg.get_codec_options()
+        assert opts["qp"] == "20"
+        assert isinstance(opts["qp"], str)
+
+    @require_libsvtav1
+    def test_structured_fields_win_on_collision(self):
+        """A colliding extra_options key is discarded; the structured field wins."""
+        cfg = VideoEncoderConfig(crf=30, extra_options={"crf": 18})
+        assert cfg.get_codec_options()["crf"] == "30"
+
+
+class TestEncoderDetection:
+    @require_h264
+    def test_explicit_codec_kept_when_available(self):
+        cfg = VideoEncoderConfig(vcodec="h264")
+        assert cfg.vcodec == "h264"
+
+    @require_videotoolbox
+    def test_auto_picks_videotoolbox_when_available(self):
+        """``h264_videotoolbox`` sits at the top of ``HW_ENCODERS`` so it wins when present."""
+        cfg = VideoEncoderConfig(vcodec="auto")
+        assert cfg.vcodec == "h264_videotoolbox"
+
+    def test_invalid_codec_raises(self):
+        with pytest.raises(ValueError, match="Invalid vcodec"):
+            VideoEncoderConfig(vcodec="not_a_real_codec")
+
+    def test_hw_encoder_names_listed_as_valid(self):
+        assert "auto" in VALID_VIDEO_CODECS
+        assert "h264_videotoolbox" in VALID_VIDEO_CODECS
+        assert "h264_nvenc" in VALID_VIDEO_CODECS
+
+
+ARTIFACTS = Path(__file__).parent.parent / "fixtures" / "artifacts" / "videos"
+
+# Default video feature set used by persistence tests.
+VIDEO_FEATURES = {
+    "observation.images.cam": {
+        "dtype": "video",
+        "shape": (64, 96, 3),
+        "names": ["height", "width", "channels"],
+    },
+    "action": {"dtype": "float32", "shape": (2,), "names": ["a", "b"]},
+}
+VIDEO_KEY = "observation.images.cam"
+
+
+def _write_frames(imgs_dir: Path, num_frames: int = 4, height: int = 64, width: int = 96) -> None:
+    imgs_dir.mkdir(parents=True, exist_ok=True)
+    for i in range(num_frames):
+        arr = np.random.randint(0, 256, (height, width, 3), dtype=np.uint8)
+        write_image(arr, imgs_dir / f"frame-{i:06d}.png")
+
+
+def _encode_video(path: Path, num_frames: int = 4, fps: int = 30, cfg: VideoEncoderConfig | None = None) -> Path:
+    imgs_dir = path.parent / f"imgs_{path.stem}"
+    _write_frames(imgs_dir, num_frames=num_frames)
+    encode_video_frames(imgs_dir, path, fps=fps, camera_encoder_config=cfg, overwrite=True)
+    return path
+
+
+def _read_feature_info(dataset: LeRobotDataset) -> dict:
+    info = json.loads((dataset.root / INFO_PATH).read_text())
+    return info["features"][VIDEO_KEY]["info"]
+
+
+def _add_frames(dataset: LeRobotDataset, num_frames: int) -> None:
+    shape = dataset.meta.features[VIDEO_KEY]["shape"]
+    for _ in range(num_frames):
+        dataset.add_frame({
+            VIDEO_KEY: np.random.randint(0, 256, shape, dtype=np.uint8),
+            "action": np.zeros(2, dtype=np.float32),
+            "task": "test",
+        })
+
+
+class TestGetVideoInfo:
+    def test_returns_all_stream_fields(self):
+        info = get_video_info(ARTIFACTS / "clip_4frames.mp4")
+
+        assert info["video.height"] == 64
+        assert info["video.width"] == 96
+        assert info["video.pix_fmt"] == "yuv420p"
+        assert info["video.fps"] == 30
+        assert info["video.channels"] == 3
+        assert info["video.is_depth_map"] is False
+        assert info["has_audio"] is False
+        assert "video.g" not in info
+        assert "video.crf" not in info
+        assert "video.preset" not in info
+
+    @require_libsvtav1
+    def test_merges_encoder_config_as_video_prefixed_entries(self):
+        cfg = VideoEncoderConfig(vcodec="libsvtav1", g=2, crf=30, preset=12)
+
+        info = get_video_info(ARTIFACTS / "clip_4frames.mp4", camera_encoder_config=cfg)
+
+        assert info["video.g"] == 2
+        assert info["video.crf"] == 30
+        assert info["video.preset"] == 12
+        assert info["video.fast_decode"] == 0
+        assert info["video.video_backend"] == "pyav"
+        assert info["video.extra_options"] == {}
+
+    @require_libsvtav1
+    def test_stream_derived_keys_take_precedence_over_config(self):
+        cfg = VideoEncoderConfig(vcodec="libsvtav1", pix_fmt="yuv420p")
+
+        info = get_video_info(ARTIFACTS / "clip_4frames.mp4", camera_encoder_config=cfg)
+
+        assert info["video.codec"]  # populated from stream, not from config's vcodec
+        assert info["video.pix_fmt"] == "yuv420p"
+
+
+class TestEncodeVideoFrames:
+    @require_libsvtav1
+    def test_produces_readable_mp4(self, tmp_path):
+        video_path = _encode_video(tmp_path / "out.mp4")
+
+        assert video_path.exists()
+        info = get_video_info(video_path)
+        assert info["video.height"] == 64
+        assert info["video.width"] == 96
+
+    @require_libsvtav1
+    def test_frame_count_and_duration_match_input(self, tmp_path):
+        num_frames = 10
+        fps = 30
+        video_path = _encode_video(tmp_path / "out.mp4", num_frames=num_frames, fps=fps)
+
+        with av.open(str(video_path)) as container:
+            stream = container.streams.video[0]
+            actual_frames = sum(1 for _ in container.decode(stream))
+            duration = (
+                float(stream.duration * stream.time_base)
+                if stream.duration is not None
+                else float(container.duration / av.time_base)
+            )
+
+        assert actual_frames == num_frames
+        assert abs(duration - num_frames / fps) < 0.1
+
+    def test_overwrite_false_skips_existing_file(self, tmp_path):
+        imgs_dir = tmp_path / "imgs"
+        _write_frames(imgs_dir)
+        video_path = tmp_path / "out.mp4"
+        sentinel = b"pre-existing content"
+        video_path.write_bytes(sentinel)
+
+        encode_video_frames(imgs_dir, video_path, fps=30, overwrite=False)
+
+        assert video_path.read_bytes() == sentinel
+
+    @require_libsvtav1
+    def test_overwrite_true_replaces_existing_file(self, tmp_path):
+        imgs_dir = tmp_path / "imgs"
+        _write_frames(imgs_dir)
+        video_path = tmp_path / "out.mp4"
+        video_path.write_bytes(b"stale content")
+
+        encode_video_frames(imgs_dir, video_path, fps=30, overwrite=True)
+
+        info = get_video_info(video_path)
+        assert info["video.height"] == 64
+
+    @require_libsvtav1
+    def test_custom_encoder_config_fields_stored_in_info(self, tmp_path):
+        """All stream-derived and encoder config fields are present after encoding."""
+        cfg = VideoEncoderConfig(vcodec="libsvtav1", g=4, crf=25, preset=10)
+        video_path = _encode_video(tmp_path / "out.mp4", num_frames=4, fps=30, cfg=cfg)
+
+        info = get_video_info(video_path, camera_encoder_config=cfg)
+
+        # Stream-derived
+        assert info["video.height"] == 64
+        assert info["video.width"] == 96
+        assert info["video.channels"] == 3
+        assert info["video.codec"] == "av1"
+        assert info["video.pix_fmt"] == "yuv420p"
+        assert info["video.fps"] == 30
+        assert info["video.is_depth_map"] is False
+        assert info["has_audio"] is False
+        # Encoder config
+        assert info["video.g"] == 4
+        assert info["video.crf"] == 25
+        assert info["video.preset"] == 10
+        assert info["video.fast_decode"] == 0
+        assert info["video.video_backend"] == "pyav"
+        assert info["video.extra_options"] == {}
+
+
+class TestConcatenateVideoFiles:
+    def test_two_clips_frame_count(self, tmp_path):
+        """Output frame count equals the sum of the two input frame counts."""
+        out = tmp_path / "out.mp4"
+        concatenate_video_files([ARTIFACTS / "clip_6frames.mp4", ARTIFACTS / "clip_4frames.mp4"], out)
+
+        with av.open(str(out)) as container:
+            total = sum(1 for _ in container.decode(video=0))
+        assert total == 10
+
+    def test_three_clips_frame_count(self, tmp_path):
+        out = tmp_path / "out.mp4"
+        clip = ARTIFACTS / "clip_5frames.mp4"
+        concatenate_video_files([clip, clip, clip], out)
+
+        with av.open(str(out)) as container:
+            total = sum(1 for _ in container.decode(video=0))
+        assert total == 15
+
+    @require_libsvtav1
+    def test_geometry_preserved(self, tmp_path):
+        """Output resolution, fps, codec and pixel format must match the inputs."""
+        out = tmp_path / "out.mp4"
+        concatenate_video_files([ARTIFACTS / "clip_4frames.mp4", ARTIFACTS / "clip_4frames.mp4"], out)
+
+        info = get_video_info(out)
+        assert info["video.height"] == 64
+        assert info["video.width"] == 96
+        assert info["video.fps"] == 30
+        assert info["video.codec"] == "av1"
+        assert info["video.pix_fmt"] == "yuv420p"
+
+    def test_compatibility_check_raises_on_different_codec(self, tmp_path):
+        with pytest.raises(ValueError):
+            concatenate_video_files(
+                [ARTIFACTS / "clip_4frames.mp4", ARTIFACTS / "clip_h264.mp4"],
+                tmp_path / "out.mp4",
+                compatibilty_check=True,
+            )
+
+    def test_compatibility_check_raises_on_different_resolution(self, tmp_path):
+        with pytest.raises(ValueError):
+            concatenate_video_files(
+                [ARTIFACTS / "clip_4frames.mp4", ARTIFACTS / "clip_32x48.mp4"],
+                tmp_path / "out.mp4",
+                compatibilty_check=True,
+            )
+
+
+class TestEncoderConfigPersistence:
+    """Encoder config must be stored as ``video.<field>`` entries in
+    ``info["features"][key]["info"]`` when the first episode is saved.
+    """
+
+    @require_libsvtav1
+    def test_first_episode_save_persists_encoder_config(self, tmp_path, empty_lerobot_dataset_factory):
+        cfg = VideoEncoderConfig(vcodec="libsvtav1", g=2, crf=30, preset=12)
+        dataset = empty_lerobot_dataset_factory(
+            root=tmp_path / "ds", features=VIDEO_FEATURES, use_videos=True, camera_encoder_config=cfg
+        )
+
+        _add_frames(dataset, num_frames=4)
+        dataset.save_episode()
+        dataset.finalize()
+
+        info = _read_feature_info(dataset)
+
+        assert info["video.height"] == 64
+        assert info["video.width"] == 96
+        assert info["video.fps"] == 30
+        assert info["video.g"] == 2
+        assert info["video.crf"] == 30
+        assert info["video.preset"] == 12
+        assert info["video.fast_decode"] == 0
+        assert info["video.video_backend"] == "pyav"
+        assert info["video.extra_options"] == {}
+
+    @require_libsvtav1
+    def test_second_episode_does_not_overwrite_encoder_fields(self, tmp_path, empty_lerobot_dataset_factory):
+        cfg = VideoEncoderConfig(vcodec="libsvtav1", g=2, crf=30, preset=12)
+        dataset = empty_lerobot_dataset_factory(
+            root=tmp_path / "ds", features=VIDEO_FEATURES, use_videos=True, camera_encoder_config=cfg
+        )
+
+        _add_frames(dataset, num_frames=4)
+        dataset.save_episode()
+        first_info = dict(_read_feature_info(dataset))
+
+        _add_frames(dataset, num_frames=4)
+        dataset.save_episode()
+        dataset.finalize()
+
+        assert _read_feature_info(dataset) == first_info

tests/fixtures/artifacts/videos/clip_32x48.mp4

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+size 5815

tests/fixtures/artifacts/videos/clip_4frames.mp4

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tests/fixtures/artifacts/videos/clip_5frames.mp4

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tests/fixtures/artifacts/videos/clip_6frames.mp4

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tests/fixtures/artifacts/videos/clip_h264.mp4

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