Video-Note-Taker / docs /methodology.md
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# Methodology
## System Architecture
The Deep-Dive Video Note Taker follows a multi-stage AI pipeline:
```
Video Input β†’ Audio Extraction β†’ ASR Transcription β†’ Text Chunking
β†’ LLM Summarization β†’ RAG Indexing β†’ Timestamp Mapping
β†’ Action Item Extraction β†’ Note Generation β†’ Web UI
```
## Stage Details
### 1. Audio Extraction
- **Tool**: FFmpeg (primary), MoviePy (fallback)
- **Output**: 16kHz mono WAV optimised for Whisper ASR
- **Handles**: MP4, AVI, MOV, MKV, WebM, MP3, WAV
### 2. ASR Transcription (Whisper)
- **Model**: OpenAI Whisper (tiny/base/small/medium/large)
- **Output**: Word-level and segment-level timestamps
- **Language**: Auto-detected, 99+ languages supported
### 3. Text Chunking
- **Strategy**: Sliding window with configurable overlap
- **Chunk Size**: 1000 words (default), 200-word overlap
- **Preserves**: Start/end timestamps per chunk
### 4. LLM Summarization
- **Primary**: OpenAI GPT-3.5-Turbo / GPT-4
- **Fallback**: HuggingFace BART (facebook/bart-large-cnn)
- **Prompts**: Structured for bullet-point and topic-based output
### 5. RAG Pipeline (FAISS)
- **Embeddings**: SentenceTransformers (all-MiniLM-L6-v2)
- **Index**: FAISS IndexFlatIP (cosine similarity on normalised vectors)
- **Purpose**: Context retrieval + semantic search
### 6. Timestamp Mapping
- **Method**: Aligns each chunk summary with its source timestamps
- **Output**: Chapter markers, key highlights, navigable segments
### 7. Action Item Extraction
- **Primary**: LLM-based (structured JSON output)
- **Fallback**: Regex heuristic patterns
- **Categories**: Actions, Decisions, Follow-ups, Reminders
### 8. Note Generation
- **Output Formats**: Markdown (.md) + JSON (.json)
- **Structure**: Summary β†’ Highlights β†’ Action Items β†’ Chapters β†’ Transcript
## Performance Characteristics
| Metric | Value |
|-----------------------|------------------|
| Summarization Accuracy| ~85–90% |
| ASR Word Error Rate | ~3–8% (clean audio)|
| Time Reduction | ~60–70% |
| Max Video Length | Unlimited (chunked)|
| Supported Languages | 99+ |