Evolve or Replace `belacoder` for Modular, H.265‑Capable, Multi‑Input Streaming

[andrescera]

Proposal: Evolve or Replace belacoder for Modular, H.265‑Capable, Multi‑Input Streaming

📌 Background

Currently, belacoder relies on hardcoded shell pipelines under pipelines/<soc>/ (e.g., rk3588) to manage SoC-specific video ingestion and streaming. While this supports minimal integration per device, it lacks:

• Runtime device/input detection
• Flexibility to switch between USB, HDMI, or network inputs
• Easy extensibility for preview or advanced streaming (SRTLA, RTMP out, etc.)
• Config-based customization (e.g., no JSON/TOML for stream params)

🎯 Objectives

1. Support multiple SoCs via pipeline modules or detection.
2. Auto-discover inputs/resolutions at runtime (USB/UVC, HDMI, RTMP/SRT).
3. Use H.265 encoding via mpph265enc or fallback to software.
4. Stream over SRT/SRTLA, RTMP, with preview via HTTP/WebRTC.
5. Clean extensibility, with JSON config or templated detection logic.

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🧪 Options Analysis

Option	Pros	Cons	Short‑Term Fit	Long‑Term Viability
A. Grow belacoder	Leverage existing scripts; no code changes	Static; no auto‑detect or preview	⚠️	⚠️ Minimal
B. Patch belacoder (C)	Quick H.265/SRTLA support; minimal edits	Limited extensibility	✅	⚠️ Moderate
C. Python + GStreamer	Dynamic pipelines; auto‑detect; built‑in Web/UI	Higher RAM; interpreter overhead	⚠️	✅ Flexible
D. Rust + gstreamer‑rs	Safe, performant; dynamic graphs	Complex toolchain; slower protos	⚠️	✅ Robust
E. C++ + GStreamer C API	Zero interpreter overhead; fine‑grained control	Boilerplate detection code	⚠️	✅ Optimal

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✅ Compatibility & Performance Matrix

Feature / Approach	A. Grow	B. Patch	C. Python	D. Rust	E. C++
H.265 (mpph265enc)	✅	✅	✅	✅	✅
USB / UVC (libuvch264)	✅ (static)	✅	✅ auto	✅	✅
HDMI (v4l2src)	✅ (static)	✅	✅ auto	✅	✅
SRT Input	✅	✅	✅	✅	✅
RTMP Input	✅	✅	✅	✅	✅
SRTLA Output	✅	✅	✅	✅	✅
RTMP Output	❌	⚠️ patch	✅	✅	✅
Preview (web/local)	❌	⚠️ patch	✅	✅	✅
Resolution detection	❌	⚠️	✅	✅	✅
RAM Usage (est.)	✅ Low	✅ Low	⚠️ 50–100MB	✅ Low	✅ Low
Latency (est.)	✅ Low	✅ Low	⚠️ ~50ms	✅ Low	✅ Low
SoC Portability	⚠️	✅	✅ via templates	✅	✅
Long-Term Evolution	⚠️ Minimal	⚠️ Moderate	✅ Strong	✅ Strong	✅ Strong

Note: RAM and latency values are based on practical experience with RK3588 + GStreamer. Python options use more RAM due to interpreter runtime. Latency numbers are relative to encoding and network overhead, assuming live pipelines.

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🧩 Proposal

Let’s choose one of the following strategies:

• 🔧 Patch belacoder: Add preview, config support, RTMP out via minimal C additions
• 🛠️ Start fresh with modular GStreamer app in Rust, Python, or C++
• ♻️ Hybrid: Extend belacoder for legacy, while building belacoder2 for new devices

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✳️ Discussion Points

• Do we want per-device detection? (e.g., USB camera vs HDMI source)
• Should preview be built-in or via separate web-ui tool?
• Should SoC-specific scripts stay in place or be replaced with detection logic?