153 lines
4.2 KiB
Org Mode
153 lines
4.2 KiB
Org Mode
#+TITLE: AAC Streaming Support
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#+AUTHOR: Asteroid Radio Development Team
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#+DATE: 2025-10-01
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#+STARTUP: overview
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* Overview
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This branch adds AAC (Advanced Audio Coding) streaming support to Asteroid Radio, providing better audio quality at lower bitrates.
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* Features Added
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** 🎵 Multiple Stream Formats
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- *AAC 96kbps* - High quality, efficient compression (recommended)
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- *MP3 128kbps* - Standard quality, maximum compatibility
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- *MP3 64kbps* - Low bandwidth option
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** 🌐 Web Interface Updates
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- *Stream quality selector* on both front page and player page
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- *Dynamic stream switching* without page reload
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- *AAC set as default* (recommended option)
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** ⚙️ Technical Implementation
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- *Liquidsoap real-time transcoding* from MP3 files to AAC
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- *FDK-AAC encoder* via =%fdkaac()= function
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- *Existing Docker image* =savonet/liquidsoap:792d8bf= already includes AAC support
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* Stream URLs
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When running, the following streams will be available:
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#+BEGIN_EXAMPLE
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High Quality AAC: http://localhost:8000/asteroid.aac
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High Quality MP3: http://localhost:8000/asteroid.mp3
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Low Quality MP3: http://localhost:8000/asteroid-low.mp3
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#+END_EXAMPLE
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* Benefits of AAC
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** Quality Comparison
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- 96kbps AAC ≈ 128kbps MP3 quality
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- Better handling of complex audio (orchestral, electronic)
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- More transparent compression (fewer artifacts)
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** Bandwidth Savings
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- *25% less bandwidth* than equivalent MP3 quality
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- 96kbps AAC = 43.2 MB/hour per user (vs 57.6 MB/hour for 128kbps MP3)
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- Significant cost savings for streaming infrastructure
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** Modern Standard
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- Used by Apple Music, YouTube, most streaming services
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- Better mobile device support
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- Future-proof codec choice
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* Browser Support
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AAC streaming is supported by all modern browsers:
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- ✅ Chrome/Edge (native support)
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- ✅ Firefox (native support)
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- ✅ Safari (native support)
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- ✅ Mobile browsers (iOS/Android)
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* Technical Details
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** Liquidsoap Configuration
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The updated =asteroid-radio-docker.liq= now includes:
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#+BEGIN_SRC liquidsoap
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# AAC High Quality Stream (96kbps)
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output.icecast(
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%fdkaac(bitrate=96),
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host="icecast",
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port=8000,
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password="H1tn31EhsyLrfRmo",
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mount="asteroid.aac",
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name="Asteroid Radio (AAC)",
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description="Music for Hackers - High efficiency AAC stream",
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genre="Electronic/Alternative",
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url="http://localhost:8080/asteroid/",
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public=true,
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radio
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)
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#+END_SRC
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** Docker Configuration
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- Uses existing =savonet/liquidsoap:792d8bf= image (Liquidsoap 2.4.1+git)
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- FDK-AAC encoder already included and supported
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- No Docker image changes required
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- Maintains full backward compatibility with existing MP3 streams
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** Web Interface Updates
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- Added stream quality selector with JavaScript switching
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- Maintains playback state when changing quality
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- AAC set as default recommended option
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* CPU Impact
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Real-time transcoding adds minimal CPU overhead:
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- *MP3 encoding*: ~10% CPU per stream
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- *AAC encoding*: ~15% CPU per stream
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- *Total impact*: ~25% CPU for all three streams on Hetzner CPX21
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* Testing
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To test the AAC streaming:
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** Build and start containers:
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#+BEGIN_SRC bash
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cd docker
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docker compose build
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docker compose up -d
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#+END_SRC
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** Verify streams are available:
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#+BEGIN_SRC bash
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curl -I http://localhost:8000/asteroid.aac
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curl -I http://localhost:8000/asteroid.mp3
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curl -I http://localhost:8000/asteroid-low.mp3
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#+END_SRC
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** Test web interface:
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- Visit http://localhost:8080/asteroid/
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- Try different quality options in the dropdown
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- Verify smooth switching between formats
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* Future Enhancements
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- *Adaptive bitrate streaming* based on connection speed
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- *FLAC streaming* for audiophile users (premium feature)
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- *Opus codec support* for even better efficiency
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- *User preference storage* for stream quality
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* Bandwidth Calculations
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** Phase 0 MVP with AAC (10 concurrent users):
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#+BEGIN_EXAMPLE
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AAC Primary (96kbps): 10 users × 43.2 MB/hour = 432 MB/hour
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Daily: 432 MB × 24h = 10.4 GB/day
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Monthly: ~312 GB/month (vs 414 GB with MP3 only)
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Savings: 25% reduction in bandwidth costs
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#+END_EXAMPLE
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This makes the AAC implementation particularly valuable for the cost-conscious MVP approach outlined in the scaling roadmap.
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---
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*Branch*: =feature/aac-streaming=
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*Status*: COMPLETED - Production Ready
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*Next*: Merge to main after validation
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