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Video Annotation

Programmatic Video Annotation Framework for ML & Content Creation

ML researchers and video content creators needed a flexible, code-driven video annotation tool that could produce annotated videos at scale, from training data preparation to educational overlays.

Discuss Your Project
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Video Annotation
Domain
8
Technologies
4
Key Results
Delivered
Status

The Challenge

Existing video annotation tools were either GUI-heavy with no programmatic API, or command-line tools with poor visualization:

  • ML teams needed bounding boxes, polygons, and labels for training data at scale
  • Educators needed animated overlays (arrows, spotlights, text) for instructional videos
  • Traditional annotation tools couldn't handle keyframe interpolation or easing animations
  • No desktop-native solution combined OpenCV processing with professional video output

Our Solution

We built a React/Remotion-based video annotation framework with a type-safe annotation system, keyframe interpolation, and a Tauri desktop editor.

Architecture

  • Video Engine: Remotion 4.0 for programmatic frame-by-frame rendering
  • Frontend: React 18 + TypeScript with Vite
  • Desktop App: Tauri 2 with OpenCV.js and ONNX Runtime
  • Export: FFmpeg for high-quality video output

Annotation Types

  1. Bounding Boxes - Rectangular regions with labels and confidence scores
  2. Circles - Point annotations with configurable radius
  3. Polygons - Complex region outlines for irregular shapes
  4. Text Labels - Styled text overlays with positioning
  5. Arrows - Directional indicators for flow or attention
  6. Freehand Paths - Custom drawn annotations
  7. Spotlights - Highlight regions with dimmed background

Animation System

  • Keyframe Interpolation - Smooth transitions between annotation states
  • Easing Functions - Spring, ease-in-out, bounce, and custom curves
  • Scene Composition - Intro, annotation layers, combined timeline, outro
  • Fade Effects - Fade-in/out with configurable duration

Key Features

  1. Type-Safe API - Comprehensive TypeScript types for all annotation primitives
  2. Scene System - Compose complex videos from scene building blocks
  3. Keyframe Animation - Animate any annotation property over time
  4. Desktop Editor - Tauri-based GUI with real-time preview
  5. Batch Export - Render annotated videos via FFmpeg
  6. OpenCV Integration - Computer vision processing in the desktop app

Results

Automation: Programmatic API enabled batch annotation of thousands of videos
Quality: Remotion rendered pixel-perfect annotations at any resolution
Flexibility: Same tool served ML training data prep and educational content
Desktop Performance: Tauri provided native-speed processing with web UI convenience

Technology Stack

ReactTypeScriptRemotion 4.0ViteTauri 2OpenCV.jsONNX RuntimeFFmpeg

Frequently Asked Questions

MicrocosmWorks built this framework for teams that need to generate annotations at scale using code-driven rules rather than human clicking. It supports writing annotation pipelines as Python scripts that apply pre-trained detectors, temporal logic, and spatial rules to automatically generate training data, then exports in COCO, Pascal VOC, or YOLO formats.

Yes, MicrocosmWorks implemented a temporal annotation model that supports frame ranges, keyframe interpolation, and event-based labels with start/end timestamps. Annotators can define temporal rules like 'label as running when pose estimation detects both feet off ground for more than 3 consecutive frames' to automate action labeling.

MicrocosmWorks built a validation pipeline that computes agreement scores between programmatic annotations and a human-reviewed golden set, flagging any annotations that fall below a configurable IoU or temporal overlap threshold. The framework also supports active learning workflows that route low-confidence annotations to human reviewers.

MicrocosmWorks built the framework on top of FFmpeg and OpenCV, supporting all major container formats including MP4, MKV, AVI, and MOV, with codecs from H.264 to ProRes. The framework processes videos at their native resolution but supports configurable downscaling for the annotation pass to accelerate throughput on large datasets.

MicrocosmWorks delivers ML infrastructure projects at rates of $25-$45/hr, with a programmatic video annotation framework including the rule engine, format exporters, and quality validation pipeline typically requiring 300-500 development hours. The framework pays for itself quickly by reducing manual annotation costs that can run $5-$15 per minute of video.

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