mtbsync 0.10.2

Align MTB GoPro runs and transfer markers using computer vision

MTB Video Sync MVP — Iterative Ticket Flow

A modular, step‑by‑step plan to build a Python MVP that aligns a new MTB GoPro run to a reference run, then transfers reference markers to the new run. Designed for use with Claude Code or the OpenAI CLI.

Quickstart

Install from PyPI:

pip install mtbsync

Basic usage:

# Index reference video
mtbsync index --reference ref.mp4 --fps 3 --out ref_index.npz

# Sync new video to reference
mtbsync sync --reference ref.mp4 --new new.mp4 --index ref_index.npz --out pairs.csv --fps 3

# Transfer markers
mtbsync transfer-markers --ref-markers ref_markers.csv --timewarp-json timewarp.json --out new_markers.csv

# Export to NLE formats
mtbsync export-markers new_markers.csv --preset fcpxml
mtbsync export-markers new_markers.csv --preset premiere
mtbsync export-markers new_markers.csv --preset resolve-edl

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Project Brief

Goal: Build a Python MVP that aligns a new MTB GoPro run to a reference run of the same trail, then transfers reference markers to the new run. Use computer vision (CV) with optional GPS. Export markers for NLEs (EDL/CSV).

Core pipeline

1. Ingest: MP4 + optional GPX/FIT.
2. Reference indexing: extract keyframes (2–5 fps), compute descriptors (start with ORB).
3. Coarse sync: (a) if GPS present → distance-based alignment; else (b) visual keyframe retrieval.
4. Fine sync: local feature matching + RANSAC → time pairs (t_new → t_ref, confidence).
5. Time‑warp fit: monotonic mapping via DTW or a monotone spline with smoothing.
6. Marker transfer: map t_ref → t_new, attach confidence; flag low‑confidence.
7. Export: CSV + CMX3600 EDL; optional FCPXML later.
8. Preview: simple Streamlit UI for side‑by‑side, scrub‑synced playback and marker review.

Non‑goals for MVP: cloud, user auth, multi‑hour videos, SuperPoint/RAFT (phase 2).

Tech: Python 3.11+, OpenCV, NumPy, SciPy, ffmpeg‑python, pandas, fastdtw, gpxpy, Streamlit, Typer/Rich.

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Repository Layout

mtb-sync/
  README.md
  pyproject.toml            # or requirements.txt
  src/
    mtbsync/__init__.py
    mtbsync/cli.py
    mtbsync/io/video.py
    mtbsync/io/gps.py
    mtbsync/features/keyframes.py
    mtbsync/features/descriptors.py
    mtbsync/match/retrieval.py
    mtbsync/match/local.py
    mtbsync/align/timewarp.py
    mtbsync/markers/schema.py
    mtbsync/markers/transfer.py
    mtbsync/export/csv_export.py
    mtbsync/export/edl_export.py
    mtbsync/ui/app.py
  tests/
    test_timewarp.py
    test_marker_transfer.py
    test_edl_export.py
  data/
    sample_reference.mp4
    sample_new.mp4
    sample_reference_markers.csv
    sample_reference.gpx

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Tickets

Work through these tickets in order. Each has acceptance criteria so an AI assistant can implement, verify, and move on cleanly.

0) Repo Scaffold

Implement

• Create the folder structure above.
• Configure packaging: pip install -e . enables local dev.
• Provide a pyproject.toml (or requirements.txt) with pinned deps.

Acceptance Criteria

• Virtual env setup works.
• mtbsync --help available after editable install.

---

1) CLI Surface

Implement

• Subcommands:

  mtbsync index --reference ref.mp4 --fps 3 --out cache/ref_index.npz
  mtbsync sync  --reference ref.mp4 --new new.mp4 \
                [--ref-gpx ref.gpx] [--new-gpx new.gpx] \
                --index cache/ref_index.npz --out cache/pairs.csv
  mtbsync warp  --pairs cache/pairs.csv --out cache/warp.npz
  mtbsync transfer --reference-markers data/ref_markers.csv --warp cache/warp.npz \
                   --out out/new_markers.csv --review-threshold 0.6
  mtbsync export edl --markers out/new_markers.csv --out out/new_markers.edl \
                     [--reel 001] [--fps 29.97]
  mtbsync preview --reference ref.mp4 --new new.mp4 --markers out/new_markers.csv
  

Acceptance Criteria

• Robust arg validation and concise summaries via rich.
• No global state; each command is independently runnable.

---

2) Video IO & Keyframes

Implement

• io/video.py:
  • extract_keyframes(video_path, fps) -> List[(t_sec, frame_bgr)]
  • video_fps(video_path) -> float
• features/keyframes.py:
  • Resize frames to max dim 960 px (preserve aspect).

Acceptance Criteria

• Deterministic timestamp sampling (handles VFR).
• Errors handled gracefully (bad file, zero‑length, etc.).

---

3) Descriptors

Implement

• features/descriptors.py with ORB (grayscale + optional CLAHE).
• Functions return keypoints and descriptors and can handle sparse scenes.

Acceptance Criteria

• Target ~800 keypoints per keyframe when available.
• Save index with timestamps, (x,y,angle,scale), and descriptors (uint8) to .npz.

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4) Retrieval (Coarse Visual Alignment)

Implement

• match/retrieval.py: brute‑force Hamming + Lowe ratio + voting to pick top‑K reference keyframes for each new keyframe.

Acceptance Criteria

• Output pairs_raw.csv with t_new, t_ref, score, n_inliers.
• 5 min @ 3 fps runs in ~≤2 minutes on a laptop.

---

5) Local Refinement

Implement

• match/local.py: For each candidate, refine around ±1 keyframe window, compute homography/affine with RANSAC, and keep best match.

Acceptance Criteria

• Output pairs.csv with (t_new, t_ref, confidence).
• Reject outliers by reprojection error; ≥70% valid pairs on sample data.

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6) GPS Alignment (Optional but Implemented)

Implement

• io/gps.py using gpxpy:
  • Parse GPX/FIT (start with GPX).
  • Compute cumulative distance and resample to 10 Hz.
• In sync, if GPS provided for either side, align distance curves (cross‑correlation) to estimate offset/scale and pre‑seed candidate t_ref.

Acceptance Criteria

• Works with one or both GPS tracks.
• Falls back cleanly to visual retrieval.

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7) Time‑Warp Fit

Implement

• align/timewarp.py:
  • Fit a monotonic mapping via fastdtw or piecewise linear monotone spline with L2 smoothing.
  • Expose map_t_new_to_t_ref(t_new) and inverse map_t_ref_to_t_new(t_ref).

Acceptance Criteria

• Strict monotonicity; median residual < 0.3 s on sample data.
• Save to warp.npz with arrays + metadata.

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8) Marker Schema & Transfer

Implement

• markers/schema.py: reference CSV schema name,t_ref,colour?,comment? (seconds float).
• markers/transfer.py: apply inverse warp to map each t_ref → t_new, interpolate confidence, flag needs_review by threshold.

Acceptance Criteria

• Output new_markers.csv with name,t_new,confidence,needs_review,comment.

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9) Exports

Implement

• export/csv_export.py: already covered by transfer CSV.
• export/edl_export.py: write CMX3600 EDL; 1‑frame events with comments.

Acceptance Criteria

• EDL imports in Resolve/Premiere with visible markers.

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10) Preview UI

Implement

• ui/app.py (Streamlit):
  • Inputs: reference/new MP4, markers CSV, warp.npz.
  • Side‑by‑side players with linked scrubbing.
  • Marker list ±5 s around playhead; colour‑coded by confidence; CSV download.

Acceptance Criteria

• streamlit run src/mtbsync/ui/app.py launches; approximate sync is acceptable.

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11) Tests & Sample Data

Implement

• Unit tests for:
  • Monotonic time‑warp and inverse mapping.
  • EDL formatting round‑trip sanity.
  • Marker transfer shape and thresholds.
• Synthetic fixtures: generate warped time with noise so tests don’t depend on large files.

Acceptance Criteria

• pytest passes in < 10 s locally.

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12) Dev Ergonomics

Implement

• Makefile/justfile: setup, lint, test, run-preview.
• Pre‑commit: ruff, black, isort.
• README.md: quick start + example commands.

Acceptance Criteria

• One‑command setup and test run.

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Prompt Templates

Claude Code (per‑ticket)

You are a senior Python engineer. Implement the next ticket in the mtb-sync repo.
Follow the acceptance criteria exactly. Keep code modular and documented.

<TICKET NAME>: <paste ticket content>

Constraints:
- Python 3.11, no GPU assumptions.
- Pure functions where possible; no global state.
- Use 'rich' for concise logging.
- Add docstrings and type hints.
- If format ambiguities arise, decide and document in README.

After changes:
- List files changed.
- Provide example CLI usage.
- Run unit tests (simulate if environment is not executable) and report results.

OpenAI CLI (chat)

openai chat.completions.create -m gpt-4.1 \
  -g "
You are a senior Python engineer. Implement the following ticket for a project called mtb-sync. Provide complete code blocks for the mentioned files. Explain only what's necessary to run it.

<TICKET NAME + CONTENT>
"

---

Quick Run Guide (for README)

# 1) Setup
python -m venv .venv && source .venv/bin/activate
pip install -U pip
pip install -e .

# 2) Index reference (3 fps keyframes)
mtbsync index --reference data/sample_reference.mp4 --fps 3 --out cache/ref_index.npz

# 3) Build pairs (with or without GPS)
mtbsync sync --reference data/sample_reference.mp4 --new data/sample_new.mp4 \
             --index cache/ref_index.npz --out cache/pairs.csv
# Optional (GPS-assisted):
mtbsync sync --reference data/sample_reference.mp4 --new data/sample_new.mp4 \
             --ref-gpx data/sample_reference.gpx --new-gpx data/sample_new.gpx \
             --index cache/ref_index.npz --out cache/pairs.csv

# 4) Fit time-warp (automatic during sync, or standalone)
# Note: sync command automatically generates timewarp.json during retrieval
mtbsync warp --pairs cache/pairs.csv --out cache/warp.npz

# 5) Transfer markers (using timewarp.json from sync)
mtbsync transfer-markers --ref-markers data/sample_reference_markers.csv \
                         --timewarp-json timewarp.json \
                         --out out/new_markers.csv \
                         --plot-overlay
# Outputs:
#   - new_markers.csv with marker_id,t_ref,t_new_est (+ preserved metadata)
#   - new_markers_overlay.png preview

# 6) Export EDL
mtbsync export edl --markers out/new_markers.csv --out out/new_markers.edl --fps 29.97

# 7) Preview UI
streamlit run src/mtbsync/ui/app.py

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Performance

Parallel Retrieval

Use --threads to enable multi-threaded frame matching:

mtbsync sync --reference ref.mp4 --new new.mp4 --index ref.npz --out pairs.csv --threads 4

Fast Preset for Bulk Jobs

Use --fast to auto-tune parameters for large-scale processing:

mtbsync sync --reference ref.mp4 --new new.mp4 --index ref.npz --out pairs.csv --fast

The --fast preset automatically:

• Sets threads >= 4 (parallel retrieval)
• Tunes warp parameters for speed (relaxed RANSAC iterations/thresholds)

Timing Information

The sync command prints per-stage timings:

• retrieval_sec - Frame matching time
• warp_sec - Time-warp fitting/gating time
• markers_sec - Marker auto-export time
• total_sec - End-to-end pipeline time

Batch processing writes timings to batch_summary.csv for analysis across multiple pairs.

⚡ Performance Benchmarks

Stage	Mean Time (s)	Notes
GPS Alignment	0.28	Vectorised (np.interp) fast-path
Retrieval	1.42	4 threads (ThreadPoolExecutor)
Warp Fit	0.06	RANSAC + IRLS refinement
Marker Export	0.11	CSV → JSON + overlay
Total	1.87 ± 0.15	Typical 1080p pair (8 k frames)

💡 Use --threads 4 or --fast for large jobs. batch_summary.csv records per-stage timings for every pair.

Dashboard

Launch a local, zero-dependency dashboard to inspect artefacts:

# read-only
mtbsync dashboard --root ./batch_out --port 8000

# enable server-side export
mtbsync dashboard --root ./batch_out --port 8000 --allow-write

Features:

• Marker selector (multiple new_markers*.csv)
• Timing sparklines from batch_summary.csv
• Download artefacts; optional POST /api/export-json when --allow-write is set

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Phase 2 (Later Tickets)

• Add SuperPoint + SuperGlue path (--matcher super).
• RAFT optical flow refinement around matched frames.
• FCPXML export for Final Cut; Premiere Pro XML.
• Manual anchor pairs UI to re‑fit time‑warp interactively.
• SQLite cache for descriptor indexes and run metadata.
• Basic metrics dashboard (pair coverage, residuals, confidence histogram).

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Why an iterative ticket flow?
It enforces small, testable steps with explicit acceptance criteria, which yields cleaner commits, faster debugging, and easier refactors as the project grows.