docs(warning): adding warning regarding encoding parameters modification

docs/source/video_encoding_parameters.mdx

@@ -43,6 +43,13 @@ lerobot-record \
 
 ## Tuning parameters
 
+<Tip warning={true}>
+The defaults are tuned to balance **compression ratio**, **visual quality**, and **decoding/seek speed** for typical robotics datasets. Changing them can affect both recording (CPU load, frame drops) and training (decoding throughput, image quality).
+
+Only override these parameters if you have a specific reason to, and measure the impact on your pipeline before relying on the new settings.
+
+</Tip>
+
 All flags below are prefixed with `--dataset.camera_encoder.` on the CLI.
 
 | Parameter       | Type           | Default       | Description                                                                                                                                                                            |

src/lerobot/datasets/aggregate.py

@@ -81,7 +81,7 @@ def merge_video_feature_info_for_aggregate(all_metadata: list[LeRobotDatasetMeta
         if fallback_keys:
             logging.warning(
                 f"Merging heterogeneous or incomplete video encoder metadata for feature {vk}. "
-                f"Setting these keys to null (video.extra_options -> {fallback_keys}).",
+                f"Setting these keys to null: {fallback_keys}.",
             )
 
         merged_info[vk]["info"] = {**base_video_info, **merged_encoder_info}