# Phase 4: Performance & Parallel Processing Implementation Plan

## Overview
Comprehensive enhancement of GrabZilla's download and conversion pipeline with parallel processing, GPU acceleration, and performance monitoring. Building upon the existing DownloadManager foundation.

**Estimated Time:** 8-12 hours
**Priority:** High - Critical for scalability and user experience
**Current Status:** Planning Phase

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## Current State Analysis

### ✅ Already Implemented
- **DownloadManager** (`src/download-manager.js`):
  - Parallel download queue with concurrency control
  - Apple Silicon detection and optimization (50% core usage for M-series)
  - Event-driven architecture with progress tracking
  - Queue management (add, cancel, stats)
  - Integrated with main.js IPC handlers

### ⚠️ Needs Enhancement
- **Download Manager**:
  - No process cancellation (can't kill active downloads)
  - No priority system for downloads
  - No retry logic for failed downloads
  - No progress events forwarded to renderer

- **FFmpeg Converter**:
  - Software encoding only (no GPU acceleration)
  - No hardware acceleration detection

- **UI**:
  - No concurrent download indicators
  - No queue visualization
  - No CPU/GPU utilization display

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## Implementation Plan

### Task 1: Enhance DownloadManager (2 hours)
- Add process tracking for cancellation
- Implement priority system (HIGH/NORMAL/LOW)
- Add retry logic with exponential backoff
- Forward progress events to renderer

### Task 2: Implement GPU Acceleration (3 hours)
- Create GPU detection module
- Update FFmpeg converter with hardware encoding
- Add GPU toggle to settings

### Task 3: UI Enhancements (2 hours)
- Add queue visualization panel
- Implement per-download progress bars
- Create performance settings panel

### Task 4: Performance Monitoring (1.5 hours)
- Create performance monitor module
- Track CPU/memory/download metrics
- Integrate with IPC

### Task 5: Testing & Benchmarking (2 hours)
- Create parallel processing tests
- Benchmark parallel vs sequential
- Benchmark GPU vs CPU conversion

**Total: 10.5 hours**

Ready to begin implementation! 🚀