more annotation changes

src/lerobot/data_processing/annotations/run_pgen.sh

@@ -4,23 +4,47 @@
 # This generates user prompts and robot utterances for hierarchical policy training
 
 # Configuration
-REPO_ID="jadechoghari/collect-data"
-MODEL="Qwen/Qwen3-VL-30B-A3B-Instruct"
+REPO_ID="jadechoghari/piper-demo-20260205_103303"
+# MODEL="Qwen/Qwen3-VL-30B-A3B-Thinking"
+MODEL="Qwen/Qwen2-VL-7B-Instruct"
 # or: MODEL="Qwen/Qwen2-VL-7B-Instruct"
 
 
 OUTPUT_DIR="/fsx/jade_choghari/outputs/collect-data-pgen_new"
 
-BATCH_SIZE=32
+BATCH_SIZE=2
 TEMPERATURE=0.9
 SAMPLE_INTERVAL=5.0  # generate dialogue every 1 second (all episodes processed)
 
-# Run subtask annotation
-python /admin/home/jade_choghari/lerobot/src/lerobot/policies/pi05_full/annotate/subtask_annotate.py \
+# Run subtask annotation.
+# To use closed-vocabulary labels, add a line: --subtask-labels "label1" "label2" ...
+# Example (add backslash after "$MODEL" and uncomment the next line):
+#   --model "$MODEL" \
+#   --subtask-labels "pick_up_yellow_nut_bar" "pick_up_cake" "pick_up_biscuit_pack" "pick_up_soda_can"
+python /admin/home/jade_choghari/lerobot/src/lerobot/data_processing/annotations/subtask_annotate.py \
     --repo-id "$REPO_ID" \
-    --video-key observation.images.base \
+    --video-key observation.images.top \
     --output-dir "$OUTPUT_DIR" \
-    --output-repo-id "jadechoghari/collect-data-with-subtasks"
+    --output-repo-id "jadechoghari/piper-demo-annotated1" \
+    --push-to-hub \
+    --model "$MODEL" \
+    --subtask-labels "pick_up_yellow_nut_bar" "pick_up_cake" "pick_up_biscuit_pack" "pick_up_soda_can" \
+    --batch-size 2
+
+# Run subtask annotation (image-window: frames as images for better accuracy)
+# python /admin/home/jade_choghari/lerobot/src/lerobot/data_processing/annotations/subtask_annotate_image.py \
+#     --repo-id "$REPO_ID" \
+#     --camera-key observation.images.wrist \
+#     --output-dir "$OUTPUT_DIR" \
+#     --output-repo-id "jadechoghari/piper-demo-annotated1-image" \
+#     --push-to-hub \
+#     --model "$MODEL" \
+#     --window-size 184 \
+#     --max-frames-per-window 16 \
+#     --subtask-labels "pick_up_yellow_nut_bar" "pick_up_cake" "pick_up_biscuit_pack" "pick_up_soda_can" \
+#     --batch-size 2
+
+    
 # run synthetic data generation (all episodes processed)
 # python examples/dataset/annotate_pgen.py \
 #     --repo-id "$REPO_ID" \

src/lerobot/data_processing/annotations/subtask_annotate.py

@@ -81,7 +81,10 @@ from rich.progress import Progress, SpinnerColumn, TextColumn
 
 from lerobot.datasets.dataset_tools import add_features
 from lerobot.datasets.lerobot_dataset import LeRobotDataset
-from lerobot.utils.constants import SKILL_SEGMENTATION_PROMPT_TEMPLATE
+from lerobot.utils.constants import (
+    SKILL_SEGMENTATION_PROMPT_TEMPLATE,
+    format_subtask_labels_section,
+)
 
 
 # Skill Annotation Data Structures
@@ -155,7 +158,7 @@ class BaseVLM(ABC):
             video_path: Path to the video file
             episode_duration: Total duration of the episode in seconds
             coarse_goal: Optional high-level task description
-            subtask_labels: Optional list of allowed skill labels to use
+            subtask_labels: If provided, model must choose only from these labels (closed vocabulary)
 
         Returns:
             List of Skill objects representing atomic manipulation skills
@@ -177,7 +180,6 @@ class BaseVLM(ABC):
             video_paths: List of paths to video files
             episode_durations: List of episode durations in seconds
             coarse_goal: Optional high-level task description
-            subtask_labels: Optional list of allowed skill labels to use
 
         Returns:
             List of skill lists, one for each video
@@ -188,33 +190,65 @@ class BaseVLM(ABC):
 def create_skill_segmentation_prompt(
     coarse_goal: str | None = None,
     subtask_labels: list[str] | None = None,
+    duration_seconds: float | None = None,
 ) -> str:
     """Create the prompt for skill segmentation.
-
-    Args:
-        coarse_goal: Optional high-level task description.
-        subtask_labels: Optional list of allowed skill/subtask labels. When provided,
-            the model is instructed to use only these labels (choosing the best match
-            for each segment).
-
-    Returns:
-        The formatted prompt string.
+    If subtask_labels is provided, uses closed-vocabulary template from constants.
+    duration_seconds is required when using subtask_labels so the model knows the full video length.
     """
     goal_context = f'The overall goal is: "{coarse_goal}"\n\n' if coarse_goal else ""
+
     if subtask_labels:
-        labels_str = ", ".join(f'"{label}"' for label in subtask_labels)
-        subtask_labels_section = (
-            f'6. **Allowed labels**: Use ONLY the following skill names '
-            f"(choose the best match for each segment): {labels_str}\n\n"
-        )
-    else:
-        subtask_labels_section = ""
-    return textwrap.dedent(
-        SKILL_SEGMENTATION_PROMPT_TEMPLATE.format(
+        if duration_seconds is None:
+            raise ValueError("duration_seconds is required when using subtask_labels (closed vocabulary)")
+        subtask_labels_section = format_subtask_labels_section(subtask_labels)
+        video_duration_mm_ss = f"{int(duration_seconds // 60):02d}:{int(duration_seconds % 60):02d}"
+        return SKILL_SEGMENTATION_PROMPT_TEMPLATE.format(
             goal_context=goal_context,
             subtask_labels_section=subtask_labels_section,
+            video_duration_seconds=duration_seconds,
+            video_duration_mm_ss=video_duration_mm_ss,
         )
+
+    duration_note = (
+        f"\nThe total video duration is **{duration_seconds} seconds**. "
+        "All start/end values must be in seconds (float). The last skill's \"end\" must be exactly this duration.\n\n"
+        if duration_seconds is not None
+        else ""
     )
+    return textwrap.dedent(f"""\
+        # Role
+        You are a Robotics Vision System specializing in temporal action segmentation for robot manipulation demonstrations.
+
+        # Task
+        {duration_note}{goal_context}Segment this robot demonstration video into short atomic manipulation skills. Each skill should:
+        - Last approximately 1-3 seconds
+        - Describe a clear, single action (e.g., "pick up object", "move arm left", "release gripper")
+        - Have precise start and end timestamps
+
+        # Requirements
+        1. **Atomic Actions**: Each skill should be a single, indivisible action
+        2. **Complete Coverage**: Skills must cover the entire video duration with no gaps
+        3. **Boundary Consistency**: The end of one skill equals the start of the next
+        4. **Natural Language**: Use clear, descriptive names for each skill
+        5. **Timestamps**: Use seconds (float) for all timestamps. If the video has a visible timer in the corner showing elapsed time in seconds, use it to report accurate start and end times for each skill.
+
+
+
+        # Output Format
+        After your analysis, output ONLY valid JSON with this exact structure:
+
+        ```json
+        {{
+          "skills": [
+            {{"name": "skill description", "start": 0.0, "end": 1.5}},
+            {{"name": "another skill", "start": 1.5, "end": 3.2}}
+          ]
+        }}
+        ```
+
+        The first skill must start at 0.0 and the last skill must end at the video duration.
+        """)
 
 
 # Qwen2-VL Implementation
@@ -249,7 +283,9 @@ class Qwen2VL(BaseVLM):
         subtask_labels: list[str] | None = None,
     ) -> list[Skill]:
         """Segment video into skills using Qwen2-VL."""
-        prompt = create_skill_segmentation_prompt(coarse_goal, subtask_labels)
+        prompt = create_skill_segmentation_prompt(
+            coarse_goal, subtask_labels, duration_seconds=episode_duration
+        )
         duration_str = f"{int(episode_duration // 60):02d}:{int(episode_duration % 60):02d}"
 
         messages = [
@@ -260,7 +296,7 @@ class Qwen2VL(BaseVLM):
                     {"type": "video", "video": str(video_path), "fps": 1.0},
                     {
                         "type": "text",
-                        "text": f"Video duration: {duration_str} (~{episode_duration:.1f}s). Segment into atomic skills.",
+                        "text": f"Video duration: {duration_str} (exactly {episode_duration:.1f} seconds). Segment into atomic skills. Last skill must end at {episode_duration:.1f}.",
                     },
                 ],
             },
@@ -294,11 +330,12 @@ class Qwen2VL(BaseVLM):
         subtask_labels: list[str] | None = None,
     ) -> list[list[Skill]]:
         """Segment multiple videos into skills using Qwen2-VL in a batch."""
-        prompt = create_skill_segmentation_prompt(coarse_goal, subtask_labels)
-        
-        # Create messages for each video
+        # Create messages for each video (prompt includes duration so each gets correct length)
         all_messages = []
         for video_path, duration in zip(video_paths, episode_durations):
+            prompt = create_skill_segmentation_prompt(
+                coarse_goal, subtask_labels, duration_seconds=duration
+            )
             duration_str = f"{int(duration // 60):02d}:{int(duration % 60):02d}"
             messages = [
                 {"role": "system", "content": [{"type": "text", "text": prompt}]},
@@ -308,7 +345,7 @@ class Qwen2VL(BaseVLM):
                         {"type": "video", "video": str(video_path), "fps": 1.0},
                         {
                             "type": "text",
-                            "text": f"Video duration: {duration_str} (~{duration:.1f}s). Segment into atomic skills.",
+                            "text": f"Video duration: {duration_str} (exactly {duration:.1f} seconds). Segment into atomic skills. Last skill must end at {duration:.1f}.",
                         },
                     ],
                 },
@@ -413,9 +450,10 @@ class Qwen3VL(BaseVLM):
         subtask_labels: list[str] | None = None,
     ) -> list[Skill]:
         """Segment video into skills using Qwen3-VL."""
-        prompt = create_skill_segmentation_prompt(coarse_goal, subtask_labels)
+        prompt = create_skill_segmentation_prompt(
+            coarse_goal, subtask_labels, duration_seconds=episode_duration
+        )
         duration_str = f"{int(episode_duration // 60):02d}:{int(episode_duration % 60):02d}"
-
         messages = [
             {"role": "system", "content": [{"type": "text", "text": prompt}]},
             {
@@ -424,7 +462,7 @@ class Qwen3VL(BaseVLM):
                     {"type": "video", "video": str(video_path), "fps": 1.0},
                     {
                         "type": "text",
-                        "text": f"Video duration: {duration_str} (~{episode_duration:.1f}s). Segment into atomic skills.",
+                        "text": f"Video duration: {duration_str} (exactly {episode_duration:.1f} seconds). Segment into atomic skills. Last skill must end at {episode_duration:.1f}.",
                     },
                 ],
             },
@@ -439,7 +477,6 @@ class Qwen3VL(BaseVLM):
             padding=True,
             return_tensors="pt",
         ).to(self.device)
-
         with torch.no_grad():
             generated_ids = self.model.generate(**inputs, max_new_tokens=1024, do_sample=True, temperature=0.7)
 
@@ -458,11 +495,12 @@ class Qwen3VL(BaseVLM):
         subtask_labels: list[str] | None = None,
     ) -> list[list[Skill]]:
         """Segment multiple videos into skills using Qwen3-VL in a batch."""
-        prompt = create_skill_segmentation_prompt(coarse_goal, subtask_labels)
-        
-        # Create messages for each video
+        # Create messages for each video (prompt includes duration so each gets correct length)
         all_messages = []
         for video_path, duration in zip(video_paths, episode_durations):
+            prompt = create_skill_segmentation_prompt(
+                coarse_goal, subtask_labels, duration_seconds=duration
+            )
             duration_str = f"{int(duration // 60):02d}:{int(duration % 60):02d}"
             messages = [
                 {"role": "system", "content": [{"type": "text", "text": prompt}]},
@@ -472,7 +510,7 @@ class Qwen3VL(BaseVLM):
                         {"type": "video", "video": str(video_path), "fps": 1.0},
                         {
                             "type": "text",
-                            "text": f"Video duration: {duration_str} (~{duration:.1f}s). Segment into atomic skills.",
+                            "text": f"Video duration: {duration_str} (exactly {duration:.1f} seconds). Segment into atomic skills. Last skill must end at {duration:.1f}.",
                         },
                     ],
                 },
@@ -660,6 +698,58 @@ class VideoExtractor:
 
         return tmp_path
 
+    def add_timer_overlay(self, video_path: Path) -> Path:
+        """
+        Add a visible timer overlay to each frame (elapsed time in seconds) in one corner.
+        Used so the VLM can read the timestamp from the image instead of relying on file metadata.
+        Writes to a new temporary file and returns its path.
+        """
+        out_file = tempfile.NamedTemporaryFile(suffix=".mp4", delete=False)
+        out_path = Path(out_file.name)
+        out_file.close()
+
+        cap = cv2.VideoCapture(str(video_path))
+        fps = cap.get(cv2.CAP_PROP_FPS) or 1.0
+        w = int(cap.get(cv2.CAP_PROP_FRAME_WIDTH))
+        h = int(cap.get(cv2.CAP_PROP_FRAME_HEIGHT))
+        fourcc = cv2.VideoWriter_fourcc(*"mp4v")
+        writer = cv2.VideoWriter(str(out_path), fourcc, fps, (w, h))
+
+        # Font scale so timer is big and readable (proportional to frame size)
+        font_scale = max(1.2, min(h, w) / 350.0)
+        thickness = max(2, int(font_scale))
+        font = cv2.FONT_HERSHEY_SIMPLEX
+
+        frame_idx = 0
+        while True:
+            ret, frame = cap.read()
+            if not ret:
+                break
+            t_sec = frame_idx / fps
+            text = f"{t_sec:.1f} s"
+            # Position: top-right corner with margin
+            (tw, th), _ = cv2.getTextSize(text, font, font_scale, thickness)
+            x = w - tw - 30
+            y = 25 + th
+            # Black outline for readability on any background (draw in 8 directions then center)
+            for dx in (-2, -1, 0, 1, 2):
+                for dy in (-2, -1, 0, 1, 2):
+                    if dx != 0 or dy != 0:
+                        cv2.putText(
+                            frame, text, (x + dx, y + dy), font, font_scale, (0, 0, 0), thickness
+                        )
+            cv2.putText(frame, text, (x, y), font, font_scale, (255, 255, 255), thickness)
+            writer.write(frame)
+            frame_idx += 1
+
+        cap.release()
+        writer.release()
+        if not out_path.exists() or out_path.stat().st_size < 1024:
+            if out_path.exists():
+                out_path.unlink()
+            raise RuntimeError("Timer overlay produced invalid file")
+        return out_path
+
     def get_video_duration(self, video_path: Path) -> float:
         """Get duration of a video file in seconds."""
         cap = cv2.VideoCapture(str(video_path))
@@ -687,11 +777,13 @@ class SkillAnnotator:
         video_extractor: VideoExtractor | None = None,
         console: Console | None = None,
         batch_size: int = 8,
+        add_timer_overlay: bool = True,
     ):
         self.vlm = vlm
         self.console = console or Console()
         self.video_extractor = video_extractor or VideoExtractor(self.console)
         self.batch_size = batch_size
+        self.add_timer_overlay = add_timer_overlay
 
     def annotate_dataset(
         self,
@@ -709,7 +801,7 @@ class SkillAnnotator:
             video_key: Key for video observations (e.g., "observation.images.base")
             episodes: Specific episode indices to annotate (None = all)
             skip_existing: Skip episodes that already have skill annotations
-            subtask_labels: Optional list of allowed skill labels (VLM will use only these)
+            subtask_labels: If provided, model must choose only from these labels (closed vocabulary)
 
         Returns:
             Dictionary mapping episode index to EpisodeSkills
@@ -854,6 +946,8 @@ class SkillAnnotator:
         """Annotate multiple episodes with skill labels in a batch."""
         # Extract all videos for this batch
         extracted_paths = []
+        timer_paths = []
+        paths_for_vlm = []
         durations = []
         valid_episode_indices = []
         
@@ -876,8 +970,16 @@ class SkillAnnotator:
                 extracted_path = self.video_extractor.extract_episode_video(
                     video_path, start_ts, end_ts, target_fps=1
                 )
-                
-                extracted_paths.append(extracted_path)
+                if self.add_timer_overlay:
+                    video_for_vlm = self.video_extractor.add_timer_overlay(extracted_path)
+                    extracted_paths.append(extracted_path)
+                    timer_paths.append(video_for_vlm)
+                else:
+                    video_for_vlm = extracted_path
+                    extracted_paths.append(extracted_path)
+                    timer_paths.append(None)
+
+                paths_for_vlm.append(video_for_vlm)
                 durations.append(duration)
                 valid_episode_indices.append(ep_idx)
                 
@@ -885,13 +987,13 @@ class SkillAnnotator:
                 self.console.print(f"[yellow]Warning: Failed to extract video for episode {ep_idx}: {e}[/yellow]")
                 continue
         
-        if not extracted_paths:
+        if not paths_for_vlm:
             return {}
         
         try:
             # Run VLM skill segmentation in batch
             all_skills = self.vlm.segment_skills_batch(
-                extracted_paths, durations, coarse_goal, subtask_labels
+                paths_for_vlm, durations, coarse_goal, subtask_labels
             )
             
             # Map results back to episode indices
@@ -902,10 +1004,13 @@ class SkillAnnotator:
             return results
             
         finally:
-            # Clean up all temporary files
+            # Clean up all temporary files (extracted and timer-overlay)
             for path in extracted_paths:
                 if path.exists():
                     path.unlink()
+            for path in timer_paths:
+                if path is not None and path.exists():
+                    path.unlink()
 
     def _annotate_episode(
         self,
@@ -932,17 +1037,23 @@ class SkillAnnotator:
         extracted_path = self.video_extractor.extract_episode_video(
             video_path, start_ts, end_ts, target_fps=1
         )
+        if self.add_timer_overlay:
+            video_for_vlm = self.video_extractor.add_timer_overlay(extracted_path)
+        else:
+            video_for_vlm = extracted_path
 
         try:
             # Run VLM skill segmentation
             skills = self.vlm.segment_skills(
-                extracted_path, duration, coarse_goal, subtask_labels
+                video_for_vlm, duration, coarse_goal, subtask_labels
             )
             return skills
         finally:
-            # Clean up temporary file
+            # Clean up temporary files (extracted and optionally timer-overlay)
             if extracted_path.exists():
                 extracted_path.unlink()
+            if self.add_timer_overlay and video_for_vlm != extracted_path and video_for_vlm.exists():
+                video_for_vlm.unlink()
 
 
 # Metadata Writer - Updates per-frame task_index based on skills
@@ -1301,13 +1412,6 @@ def main():
         action="store_true",
         help="Skip episodes that already have annotations",
     )
-    parser.add_argument(
-        "--subtask-labels",
-        type=str,
-        nargs="+",
-        default=None,
-        help="Optional list of allowed skill labels (VLM will use only these; space-separated)",
-    )
 
     # Output options
     parser.add_argument(
@@ -1325,6 +1429,18 @@ def main():
         type=str,
         help="Repository ID for the new dataset (default: original_repo_id_with_subtasks)",
     )
+    parser.add_argument(
+        "--subtask-labels",
+        type=str,
+        nargs="*",
+        default=None,
+        help="Closed vocabulary: model must choose only from these labels",
+    )
+    parser.add_argument(
+        "--no-timer-overlay",
+        action="store_true",
+        help="Disable timer overlay on video (by default a timer is drawn in the corner so the VLM can read timestamps from the image)",
+    )
 
     args = parser.parse_args()
     console = Console()
@@ -1357,7 +1473,13 @@ def main():
     vlm = get_vlm(args.model, args.device, torch_dtype)
 
     # Create annotator and run annotation
-    annotator = SkillAnnotator(vlm=vlm, console=console, batch_size=args.batch_size)
+    add_timer_overlay = not args.no_timer_overlay
+    annotator = SkillAnnotator(
+        vlm=vlm,
+        console=console,
+        batch_size=args.batch_size,
+        add_timer_overlay=add_timer_overlay,
+    )
     console.print(f"[cyan]Processing with batch size: {args.batch_size}[/cyan]")
     annotations = annotator.annotate_dataset(
         dataset=dataset,
@@ -1393,4 +1515,4 @@ def main():
 
 
 if __name__ == "__main__":
-    main()
+    main()

src/lerobot/data_processing/annotations/subtask_annotate_image.py

@@ -0,0 +1,561 @@
+#!/usr/bin/env python
+
+# Copyright 2025 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.
+
+"""
+Image-window subtask annotation for LeRobot datasets using Qwen VLMs.
+
+This script assigns a subtask to each window of consecutive frames by sending
+those frames as images to the VLM (instead of a video) for better accuracy.
+Supports Qwen2-VL and Qwen3-VL (same models as subtask_annotate.py).
+
+Pipeline:
+1. Load a LeRobot dataset (local or Hub).
+2. For each episode, slide a window over frame indices.
+3. For each window, load the corresponding images (from image_key or decoded video_key).
+4. Send the window of images to Qwen2-VL with the same skill prompt; get one subtask name.
+5. Assign that subtask to all frames in the window.
+6. Write subtasks.parquet and add subtask_index via add_features (same as subtask_annotate).
+
+Usage:
+  python -m lerobot.data_processing.annotations.subtask_annotate_image \\
+    --data-dir /path/to/dataset --camera-key observation.images.base \\
+    --window-size 8 --stride 8 --output-dir ./output
+"""
+
+from __future__ import annotations
+
+import argparse
+import random
+import textwrap
+from pathlib import Path
+
+import numpy as np
+import PIL.Image
+import torch
+from rich.console import Console
+
+from lerobot.datasets.lerobot_dataset import LeRobotDataset
+
+# Reuse data structures and save/load from the video-based annotator
+from lerobot.data_processing.annotations.subtask_annotate import (
+    EpisodeSkills,
+    Skill,
+    load_skill_annotations,
+    save_skill_annotations,
+)
+
+
+def create_window_skill_prompt(
+    coarse_goal: str | None = None,
+    subtask_labels: list[str] | None = None,
+) -> str:
+    """Prompt for labeling a single window of frames with one atomic skill.
+    If subtask_labels are provided, the model must choose exactly one from that list.
+    """
+    goal_context = f'The overall goal is: "{coarse_goal}".\n\n' if coarse_goal else ""
+    if subtask_labels:
+        labels_list = ", ".join(f'"{l}"' for l in subtask_labels)
+        label_instruction = (
+            f"You must choose exactly ONE skill from this list: [{labels_list}]. "
+            "Do not create new labels. Reply with only that label.\n\n"
+        )
+    else:
+        label_instruction = ""
+    return textwrap.dedent(f"""\
+        # Role
+        You are a Robotics Vision System that labels short clips from robot manipulation demonstrations.
+
+        # Task
+        {goal_context}{label_instruction}The following images are consecutive frames from a single short clip of a robot demonstration.
+        What single atomic manipulation skill is being performed in this clip?
+
+        # Requirements
+        - Reply with ONLY one short skill name (e.g. "pick up object", "move arm left", "release gripper").
+        - No explanation, no timestamps, no JSON. Just the skill name.
+        """).strip()
+
+
+def _run_image_segmenter(
+    self,
+    images: list[PIL.Image.Image],
+    coarse_goal: str | None,
+    subtask_labels: list[str] | None = None,
+) -> str:
+    """Shared inference for Qwen2-VL and Qwen3-VL image window labeling."""
+    prompt = create_window_skill_prompt(coarse_goal, subtask_labels)
+    content = []
+    for img in images:
+        content.append({"type": "image", "image": img})
+    content.append({"type": "text", "text": "What single atomic skill is shown in these frames? Reply with only the skill name."})
+
+    messages = [
+        {"role": "system", "content": [{"type": "text", "text": prompt}]},
+        {"role": "user", "content": content},
+    ]
+    text = self.processor.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)
+    image_inputs, video_inputs = self.process_vision_info(messages)
+    inputs = self.processor(
+        text=[text],
+        images=image_inputs,
+        videos=video_inputs,
+        padding=True,
+        return_tensors="pt",
+    ).to(self.device)
+
+    with torch.no_grad():
+        generated_ids = self.model.generate(**inputs, max_new_tokens=128, do_sample=False)
+
+    response = self.processor.batch_decode(
+        [out[len(inp) :] for inp, out in zip(inputs.input_ids, generated_ids)],
+        skip_special_tokens=True,
+    )[0].strip()
+    skill_name = response.split("\n")[0].strip().strip('."')
+    return skill_name if skill_name else "unknown"
+
+
+def _run_image_segmenter_batch(
+    self,
+    batch_images: list[list[PIL.Image.Image]],
+    coarse_goal: str | None,
+    subtask_labels: list[str] | None = None,
+) -> list[str]:
+    """Run VLM on multiple windows at once; returns one skill name per window."""
+    if not batch_images:
+        return []
+    prompt = create_window_skill_prompt(coarse_goal, subtask_labels)
+    all_texts = []
+    all_image_inputs = []
+    all_video_inputs = []
+    for images in batch_images:
+        content = []
+        for img in images:
+            content.append({"type": "image", "image": img})
+        content.append({"type": "text", "text": "What single atomic skill is shown in these frames? Reply with only the skill name."})
+        messages = [
+            {"role": "system", "content": [{"type": "text", "text": prompt}]},
+            {"role": "user", "content": content},
+        ]
+        text = self.processor.apply_chat_template(messages, tokenize=False, add_generation_prompt=True)
+        image_inputs, video_inputs = self.process_vision_info(messages)
+        all_texts.append(text)
+        if image_inputs is not None:
+            all_image_inputs.extend(image_inputs if isinstance(image_inputs, list) else [image_inputs])
+        if video_inputs is not None:
+            all_video_inputs.extend(video_inputs if isinstance(video_inputs, list) else [video_inputs])
+    inputs = self.processor(
+        text=all_texts,
+        images=all_image_inputs if all_image_inputs else None,
+        videos=all_video_inputs if all_video_inputs else None,
+        padding=True,
+        return_tensors="pt",
+    ).to(self.device)
+    with torch.no_grad():
+        generated_ids = self.model.generate(**inputs, max_new_tokens=128, do_sample=False)
+    responses = self.processor.batch_decode(
+        [out[len(inp) :] for inp, out in zip(inputs.input_ids, generated_ids)],
+        skip_special_tokens=True,
+    )
+    return [
+        (r.split("\n")[0].strip().strip('."') or "unknown")
+        for r in responses
+    ]
+
+
+class Qwen2VLImageSegmenter:
+    """Uses Qwen2-VL to assign one skill name to a window of images (same model as subtask_annotate)."""
+
+    def __init__(self, model_name: str, device: str = "cuda", torch_dtype: torch.dtype = torch.bfloat16):
+        from qwen_vl_utils import process_vision_info
+        from transformers import AutoProcessor, Qwen2VLForConditionalGeneration
+
+        self.console = Console()
+        self.device = device
+        self.process_vision_info = process_vision_info
+        self.console.print(f"[cyan]Loading Qwen2-VL for image-window labeling: {model_name}...[/cyan]")
+        self.model = Qwen2VLForConditionalGeneration.from_pretrained(
+            model_name, torch_dtype=torch_dtype, device_map=device, trust_remote_code=True
+        )
+        self.processor = AutoProcessor.from_pretrained(model_name, trust_remote_code=True)
+        self.console.print(f"[green]✓ Model loaded on {device}[/green]")
+
+    def segment_skill_from_images(
+        self,
+        images: list[PIL.Image.Image],
+        coarse_goal: str | None = None,
+        subtask_labels: list[str] | None = None,
+    ) -> str:
+        """Return a single skill name for the given window of images."""
+        return _run_image_segmenter(self, images, coarse_goal, subtask_labels)
+
+    def segment_skill_from_images_batch(
+        self,
+        batch_images: list[list[PIL.Image.Image]],
+        coarse_goal: str | None = None,
+        subtask_labels: list[str] | None = None,
+    ) -> list[str]:
+        """Return one skill name per window; processes multiple windows in one forward pass."""
+        return _run_image_segmenter_batch(self, batch_images, coarse_goal, subtask_labels)
+
+
+class Qwen3VLImageSegmenter:
+    """Uses Qwen3-VL (MoE) to assign one skill name to a window of images."""
+
+    def __init__(self, model_name: str, device: str = "cuda", torch_dtype: torch.dtype = torch.bfloat16):
+        from qwen_vl_utils import process_vision_info
+        from transformers import AutoProcessor, Qwen3VLMoeForConditionalGeneration
+
+        self.console = Console()
+        self.device = device
+        self.process_vision_info = process_vision_info
+        self.console.print(f"[cyan]Loading Qwen3-VL for image-window labeling: {model_name}...[/cyan]")
+        self.model = Qwen3VLMoeForConditionalGeneration.from_pretrained(
+            model_name, torch_dtype=torch_dtype, device_map=device, trust_remote_code=True
+        )
+        self.processor = AutoProcessor.from_pretrained(model_name, trust_remote_code=True)
+        self.console.print(f"[green]✓ Model loaded on {device}[/green]")
+
+    def segment_skill_from_images(
+        self,
+        images: list[PIL.Image.Image],
+        coarse_goal: str | None = None,
+        subtask_labels: list[str] | None = None,
+    ) -> str:
+        """Return a single skill name for the given window of images."""
+        return _run_image_segmenter(self, images, coarse_goal, subtask_labels)
+
+    def segment_skill_from_images_batch(
+        self,
+        batch_images: list[list[PIL.Image.Image]],
+        coarse_goal: str | None = None,
+        subtask_labels: list[str] | None = None,
+    ) -> list[str]:
+        """Return one skill name per window; processes multiple windows in one forward pass."""
+        return _run_image_segmenter_batch(self, batch_images, coarse_goal, subtask_labels)
+
+
+def get_image_segmenter(
+    model_name: str,
+    device: str = "cuda",
+    torch_dtype: torch.dtype = torch.bfloat16,
+):
+    """Return the appropriate image-window segmenter for the model (Qwen2-VL or Qwen3-VL)."""
+    model_lower = model_name.lower()
+    if "qwen3" in model_lower:
+        return Qwen3VLImageSegmenter(model_name, device, torch_dtype)
+    return Qwen2VLImageSegmenter(model_name, device, torch_dtype)
+
+
+def frame_to_pil(frame_value) -> PIL.Image.Image:
+    """Convert a single frame from dataset (tensor or PIL or path) to PIL.Image."""
+    if isinstance(frame_value, PIL.Image.Image):
+        return frame_value
+    if isinstance(frame_value, (str, Path)):
+        return PIL.Image.open(frame_value).convert("RGB")
+    if hasattr(frame_value, "numpy"):
+        arr = frame_value.numpy()
+    else:
+        arr = np.asarray(frame_value)
+    if arr.ndim == 3 and arr.shape[0] in (1, 3, 4):
+        arr = np.transpose(arr, (1, 2, 0))
+    if arr.dtype == np.float32 or arr.dtype == np.float64:
+        arr = (np.clip(arr, 0, 1) * 255).astype(np.uint8)
+    elif arr.dtype != np.uint8:
+        arr = np.clip(arr, 0, 255).astype(np.uint8)
+    if arr.shape[-1] == 1:
+        arr = np.repeat(arr, 3, axis=-1)
+    return PIL.Image.fromarray(arr)
+
+
+def _sample_window_indices(window_length: int, max_frames: int) -> list[int]:
+    """Return indices into a window of length window_length, at most max_frames, in order.
+    If window_length <= max_frames, returns range(window_length).
+    Otherwise returns sorted random sample of max_frames indices (temporal order preserved).
+    """
+    if max_frames <= 0 or window_length <= max_frames:
+        return list(range(window_length))
+    return sorted(random.sample(range(window_length), max_frames))
+
+
+class SkillAnnotatorImage:
+    """Annotates episodes by sliding a window over frames and labeling each window with the VLM."""
+
+    def __init__(
+        self,
+        segmenter: Qwen2VLImageSegmenter | Qwen3VLImageSegmenter,
+        window_size: int = 8,
+        stride: int | None = None,
+        batch_size: int = 1,
+        max_frames_per_window: int | None = None,
+        console: Console | None = None,
+    ):
+        self.segmenter = segmenter
+        self.window_size = window_size
+        self.stride = stride if stride is not None else window_size
+        self.batch_size = max(1, batch_size)
+        self.max_frames_per_window = max_frames_per_window
+        self.console = console or Console()
+
+    def annotate_dataset(
+        self,
+        dataset: LeRobotDataset,
+        camera_key: str,
+        episodes: list[int] | None = None,
+        skip_existing: bool = False,
+        subtask_labels: list[str] | None = None,
+    ) -> dict[int, EpisodeSkills]:
+        """Annotate episodes using image windows. camera_key can be an image_key or video_key."""
+        episode_indices = episodes or list(range(dataset.meta.total_episodes))
+        coarse_goal = self._get_coarse_goal(dataset)
+        annotations: dict[int, EpisodeSkills] = {}
+
+        if skip_existing:
+            existing = load_skill_annotations(dataset.root)
+            if existing and existing.get("episodes"):
+                existing_eps = {int(k) for k in existing["episodes"] if existing["episodes"][k].get("skills")}
+                episode_indices = [i for i in episode_indices if i not in existing_eps]
+
+        for ep_idx in episode_indices:
+            try:
+                skills = self._annotate_episode(
+                    dataset, ep_idx, camera_key, coarse_goal, subtask_labels
+                )
+                if skills:
+                    annotations[ep_idx] = EpisodeSkills(
+                        episode_index=ep_idx,
+                        description=coarse_goal,
+                        skills=skills,
+                    )
+                    self.console.print(f"[green]✓ Episode {ep_idx}: {len(skills)} window skills[/green]")
+                else:
+                    self.console.print(f"[yellow]⚠ Episode {ep_idx}: no skills[/yellow]")
+            except Exception as e:
+                self.console.print(f"[red]Episode {ep_idx} failed: {e}[/red]")
+
+        return annotations
+
+    def _get_coarse_goal(self, dataset: LeRobotDataset) -> str:
+        if dataset.meta.tasks is not None and len(dataset.meta.tasks) > 0:
+            return str(dataset.meta.tasks.index[0])
+        return "Perform the demonstrated manipulation task."
+
+    def _annotate_episode(
+        self,
+        dataset: LeRobotDataset,
+        episode_index: int,
+        camera_key: str,
+        coarse_goal: str,
+        subtask_labels: list[str] | None = None,
+    ) -> list[Skill]:
+        ep = dataset.meta.episodes[episode_index]
+        ep_from = int(ep["dataset_from_index"])
+        ep_to = int(ep["dataset_to_index"])
+        length = ep_to - ep_from
+        fps = dataset.meta.fps
+        if length == 0:
+            return []
+
+        # Collect full windows: (images, t_start, t_end) using frame timestamps.
+        # If max_frames_per_window is set and window is larger, sample that many frames (order preserved).
+        window_specs: list[tuple[list[PIL.Image.Image], float, float]] = []
+        start = 0
+        while start + self.window_size <= length:
+            offsets = _sample_window_indices(
+                self.window_size,
+                self.max_frames_per_window or self.window_size,
+            )
+            frame_indices = [ep_from + start + i for i in offsets]
+            images = []
+            t_start = float(dataset[frame_indices[0]]["timestamp"].item())
+            for idx in frame_indices:
+                item = dataset[idx]
+                images.append(frame_to_pil(item[camera_key]))
+            t_end = t_start + self.window_size / fps
+            window_specs.append((images, t_start, t_end))
+            start += self.stride
+
+        # Last partial window
+        if start < length:
+            partial_len = ep_to - (ep_from + start)
+            offsets = _sample_window_indices(
+                partial_len,
+                self.max_frames_per_window or partial_len,
+            )
+            frame_indices = [ep_from + start + i for i in offsets]
+            images = []
+            t_start = float(dataset[frame_indices[0]]["timestamp"].item())
+            for idx in frame_indices:
+                item = dataset[idx]
+                images.append(frame_to_pil(item[camera_key]))
+            t_end = float(dataset[frame_indices[-1]]["timestamp"].item()) + 1.0 / fps
+            window_specs.append((images, t_start, t_end))
+
+        # Run in batches
+        skills: list[Skill] = []
+        for i in range(0, len(window_specs), self.batch_size):
+            chunk = window_specs[i : i + self.batch_size]
+            batch_images = [spec[0] for spec in chunk]
+            if len(batch_images) > 1:
+                skill_names = self.segmenter.segment_skill_from_images_batch(
+                    batch_images, coarse_goal, subtask_labels
+                )
+            else:
+                skill_names = [
+                    self.segmenter.segment_skill_from_images(
+                        batch_images[0], coarse_goal, subtask_labels
+                    )
+                ]
+            for (_, t_start, t_end), name in zip(chunk, skill_names, strict=True):
+                skills.append(Skill(name=name, start=t_start, end=t_end))
+
+        return skills
+
+
+def main():
+    parser = argparse.ArgumentParser(
+        description="Image-window subtask annotation using Qwen VLM (frames as images for better accuracy)",
+        formatter_class=argparse.RawDescriptionHelpFormatter,
+        epilog=textwrap.dedent("""\
+            Examples:
+              python -m lerobot.data_processing.annotations.subtask_annotate_image \\
+                --data-dir /path/to/dataset --camera-key observation.images.base \\
+                --window-size 8 --output-dir ./output
+
+              python -m lerobot.data_processing.annotations.subtask_annotate_image \\
+                --repo-id user/dataset --camera-key observation.images.base \\
+                --window-size 6 --stride 3 --model Qwen/Qwen2-VL-7B-Instruct
+
+              # Use Qwen3-VL (MoE)
+              python -m lerobot.data_processing.annotations.subtask_annotate_image \\
+                --data-dir /path/to/dataset --camera-key observation.images.base \\
+                --model Qwen/Qwen3-VL-30B-A3B-Instruct
+        """),
+    )
+    data_group = parser.add_mutually_exclusive_group(required=True)
+    data_group.add_argument("--data-dir", type=str, help="Path to local LeRobot dataset")
+    data_group.add_argument("--repo-id", type=str, help="HuggingFace Hub dataset repository ID")
+
+    parser.add_argument(
+        "--camera-key",
+        type=str,
+        required=True,
+        help="Image or video observation key (e.g. observation.images.base)",
+    )
+    parser.add_argument(
+        "--model",
+        type=str,
+        default="Qwen/Qwen2-VL-7B-Instruct",
+        help="VLM model: Qwen2-VL or Qwen3-VL (default: Qwen/Qwen2-VL-7B-Instruct)",
+    )
+    parser.add_argument(
+        "--device",
+        type=str,
+        default="cuda",
+    )
+    parser.add_argument(
+        "--window-size",
+        type=int,
+        default=8,
+        help="Number of frames per window (default: 8)",
+    )
+    parser.add_argument(
+        "--stride",
+        type=int,
+        default=None,
+        help="Stride for sliding window (default: window_size = non-overlapping)",
+    )
+    parser.add_argument(
+        "--batch-size",
+        type=int,
+        default=1,
+        help="Number of windows to process in one VLM call (default: 1; increase for speed)",
+    )
+    parser.add_argument(
+        "--max-frames-per-window",
+        type=int,
+        default=None,
+        metavar="N",
+        help="If window has more than N frames, randomly sample N frames (order kept) to avoid OOM (e.g. 16)",
+    )
+    parser.add_argument("--episodes", type=int, nargs="+", help="Episode indices to annotate (default: all)")
+    parser.add_argument("--skip-existing", action="store_true", help="Skip episodes that already have annotations")
+    parser.add_argument(
+        "--subtask-labels",
+        type=str,
+        nargs="*",
+        default=None,
+        help="Closed vocabulary: model must choose only from these labels",
+    )
+    parser.add_argument("--output-dir", type=str, help="Output directory for dataset with subtask_index")
+    parser.add_argument("--output-repo-id", type=str, help="Output repo id (default: <repo_id>_with_subtasks)")
+    parser.add_argument("--push-to-hub", action="store_true")
+
+    args = parser.parse_args()
+    console = Console()
+
+    # Load dataset
+    console.print("[cyan]Loading dataset...[/cyan]")
+    if args.data_dir:
+        dataset = LeRobotDataset(repo_id="local/dataset", root=args.data_dir, download_videos=False)
+    else:
+        dataset = LeRobotDataset(repo_id=args.repo_id, download_videos=True)
+    camera_keys = dataset.meta.camera_keys
+    if args.camera_key not in camera_keys:
+        console.print(f"[red]Error: camera key '{args.camera_key}' not in {camera_keys}[/red]")
+        return
+    console.print(f"[green]✓ Loaded dataset, {dataset.meta.total_episodes} episodes[/green]")
+
+    # Same Qwen VLM as subtask_annotate (Qwen2-VL or Qwen3-VL), image windows instead of video
+    segmenter = get_image_segmenter(args.model, args.device, torch.bfloat16)
+
+    annotator = SkillAnnotatorImage(
+        segmenter=segmenter,
+        window_size=args.window_size,
+        stride=args.stride,
+        batch_size=args.batch_size,
+        max_frames_per_window=args.max_frames_per_window,
+        console=console,
+    )
+    annotations = annotator.annotate_dataset(
+        dataset=dataset,
+        camera_key=args.camera_key,
+        episodes=args.episodes,
+        skip_existing=args.skip_existing,
+        subtask_labels=args.subtask_labels,
+    )
+
+    if not annotations:
+        console.print("[yellow]No annotations to save.[/yellow]")
+        return
+
+    output_dir = Path(args.output_dir) if args.output_dir else None
+    output_repo_id = args.output_repo_id
+    new_dataset = save_skill_annotations(dataset, annotations, output_dir, output_repo_id)
+
+    total_skills = sum(len(a.skills) for a in annotations.values())
+    console.print(f"[bold green]✓ Done.[/bold green] Episodes: {len(annotations)}, total window skills: {total_skills}")
+    console.print(f"  Dataset with subtask_index: {new_dataset.root}")
+
+    if args.push_to_hub and not args.data_dir:
+        console.print("[cyan]Pushing to Hub...[/cyan]")
+        try:
+            new_dataset.push_to_hub(push_videos=False)
+            console.print("[green]✓ Pushed.[/green]")
+        except Exception as e:
+            console.print(f"[red]Push failed: {e}[/red]")
+
+
+if __name__ == "__main__":
+    main()

src/lerobot/utils/constants.py

@@ -95,34 +95,106 @@ LIBERO_KEY_PIXELS_EYE_IN_HAND = "pixels/robot0_eye_in_hand_image"
 
 # Skill segmentation prompt template for VLM-based subtask annotation
 # Placeholders: {goal_context}, {subtask_labels_section}
+# When subtask_labels are provided, use format_subtask_labels_section() to fill {subtask_labels_section}.
+
+
+def format_subtask_labels_section(subtask_labels: list[str]) -> str:
+    """Format a list of subtask labels for insertion into SKILL_SEGMENTATION_PROMPT_TEMPLATE.
+    The model will be instructed to choose only from these labels.
+    """
+    if not subtask_labels:
+        return ""
+    return "\n".join(f'    "{label}",' for label in subtask_labels).rstrip(",")
+
+
 SKILL_SEGMENTATION_PROMPT_TEMPLATE = """# Role
 You are a Robotics Vision System specializing in temporal action segmentation for robot manipulation demonstrations.
 
+# Video duration (critical)
+The total video length is **{video_duration_seconds} seconds** ({video_duration_mm_ss}). All "start" and "end" values in your JSON must be numeric seconds in the range [0.0, {video_duration_seconds}]. The last skill's "end" must be exactly **{video_duration_seconds}**. Do not stop earlier.
+
 # Task
 {goal_context}Segment this robot demonstration video into short atomic manipulation skills. Each skill should:
-- Last approximately 1-3 seconds
+- Last approximately 1-3 seconds (or longer if the action takes longer)
 - Describe a clear, single action (e.g., "pick up object", "move arm left", "release gripper")
-- Have precise start and end timestamps
+- Have precise start and end timestamps in seconds (float)
 
 # Requirements
 1. **Atomic Actions**: Each skill should be a single, indivisible action
-2. **Complete Coverage**: Skills must cover the entire video duration with no gaps
+2. **Complete Coverage**: Skills must cover the entire video from 0.0 to {video_duration_seconds} seconds with no gaps
 3. **Boundary Consistency**: The end of one skill equals the start of the next
 4. **Natural Language**: Use clear, descriptive names for each skill
-5. **Timestamps**: Use seconds (float) for all timestamps
-{subtask_labels_section}
+5. **Timestamps**: Use seconds as floats (e.g. 12.5) for all timestamps; the last "end" must be {video_duration_seconds}. If the video has a visible timer in the corner showing elapsed time in seconds, use it to report accurate start and end times for each skill.
+# Subtask Label Set (Closed Vocabulary)
+        You MUST strictly identify the video segments using ONLY the following labels. Do not create new labels or modify existing ones:
+
+        [
+        {subtask_labels_section}
+        ]
+
+        The video shows one successful execution of all subtasks in a logical order.
+
+        # Ground-Truth Semantics (Very Important)
+        Use **visual state changes** to define when a subtask starts and ends. Do NOT assume equal durations for the subtasks.
+
+        - A subtask **starts** at the first frame where the robot's motion clearly initiates that subtask.
+        - A subtask **ends** at the first frame where that specific action is visually completed and the manipulated object reaches a temporary, stable configuration.
+
+        If there are short pauses or micro-motions that don't clearly correspond to a new subtask, they belong to the **current** subtask.
+
+        # Hard Constraints & Logic
+        1. **Continuous Coverage (No Gaps):**
+           - The entire video from 0.0 to {video_duration_seconds} seconds must be covered by subtasks.
+           - There can be no gaps between subtasks.
+           - If there is any idle or ambiguous time between clear actions, extend the *preceding* subtask to cover it.
+
+        2. **Boundary Consistency:**
+           - The `"end"` timestamp of one subtask must be exactly equal to the `"start"` timestamp of the next subtask.
+           - Boundaries must coincide with a real visual state transition, not just a convenient time split.
+
+        3. **Chronological Order, One Occurrence Each:**
+           - This is a single successful demonstration.
+           - Each subtask from the vocabulary appears **exactly once**, in the correct logical order.
+           - **Durations may be very different** between subtasks. Never assume they are similar lengths. Base all boundaries only on the video.
+
+        4. **Reject Uniform Segmentation (Important):**
+           - Do NOT simply divide the video into equal or nearly equal time chunks.
+           - If your boundaries would result in subtasks with similar durations (e.g. all around 5 seconds), treat this as evidence that your segmentation is wrong and refine the boundaries.
+           - Only use nearly equal durations if the video truly shows each subtask taking the same amount of time (this is very rare).
+
+        5. **Timestamps (critical):**
+           - Use numeric seconds (float) in the JSON, e.g. 0.0, 5.2, 12.8.
+           - The first subtask always starts at 0.0.
+           - The last subtask must end at exactly {video_duration_seconds} (the full video length).
+           - **Time is displayed inside the video**: a visible timer in one corner shows the elapsed time in seconds (from 0.0 to the end). Use this on-screen timer to set accurate start and end times for each skill.
+
+        # Step 1 — Textual Timeline (must do this first)
+        First, write a extensive and detailed textual timeline describing what happens in the video with approximate timestamps. **Read the time from the visible timer shown in the video** to get accurate timestamps.
+        For each subtask, include:
+        - its name
+        - an approximate start and end time (from the on-screen timer),
+        - an description of the visual event at the boundary (e.g. "shirt fully folded to the left", "robot rotates folded shirt 90 degrees").
+
+        Format this as a bullet list.
 
 # Output Format
-After your analysis, output ONLY valid JSON with this exact structure:
+After your analysis, output ONLY valid JSON with this exact structure. The last skill's "end" MUST be exactly {video_duration_seconds}. Use the timestamps you read from the visible timer in the video:
 
 ```json
 {{
   "skills": [
-    {{"name": "skill description", "start": 0.0, "end": 1.5}},
-    {{"name": "another skill", "start": 1.5, "end": 3.2}}
+    {{"name": "first skill", "start": 0.0, "end": 5.0}},
+    {{"name": "second skill", "start": 5.0, "end": 12.0}},
+    {{"name": "last skill", "start": 12.0, "end": {video_duration_seconds}}}
   ]
 }}
 ```
 
-The first skill must start at 0.0 and the last skill must end at the video duration.
+The first skill must start at 0.0 and the last skill must end at **{video_duration_seconds}** (the total video duration in seconds).
+# Strict Structural Rule
+This video contains exactly 4 subtasks.
+You MUST output exactly 4 segments.
+Each segment must use a unique label from the vocabulary.
+No label may be repeated.
+
 """