Talon
5f6c223526
Closes the three items PROGRESS.md's M3 section explicitly carried forward as out of scope: - Device enumeration (vc_list_devices) + input device selection (vc_set_input_device), backed by AudioEngine::enumerate_devices() via miniaudio's ma_context_get_devices. Device ids are opaque hex-encoded ma_device_id strings. - VAD/PTT send-side input gate (vc_set_input_mode, vc_set_push_to_talk). webrtc-audio-processing (the originally-planned APM) has no working Windows/MSVC build upstream (GCC-only Meson, unfinished MinGW support, hard abseil-cpp dependency), so VAD is a new lightweight, dependency-free energy/RMS processor (EnergyVadProcessor) behind the existing ApmProcessor interface. Gating is MIC-only; SCREEN_AUDIO/AUX_DEVICE always bypass it. - True stereo playback: AudioEngine's mixer and output device now carry stereo end-to-end (mono streams upmix L=R) instead of downmixing decoded stereo streams to mono before mixing. - Real WASAPI loopback capture for SCREEN_AUDIO (Windows-only, via miniaudio's loopback device type), replacing test-only injection as the production capture path. Also: vccli gains --list-devices, --input-device, --input-mode, and --share-screen-audio flags, plus a stdin command loop (ptt on/off, mode vad/ptt) for manual verification. New test_vad_ptt_devices.cpp covers all four items (ABI-level + a white-box AudioEngine stereo-mix check). Docs updated to match: voice.md, roadmap.md (decision-log entry superseding the original webrtc-audio-processing choice), tech-stack.md, README.md, architecture.md, CLAUDE.md, PROGRESS.md. Still explicitly out of scope, documented not silently dropped: real webrtc-audio-processing/AEC (no AEC/NS/AGC exists at all yet), macOS/iOS SCREEN_AUDIO capture, process-specific loopback, and a pre-existing RT-thread rule violation in the capture path that predates this work. Verified: ctest 12/12 green across 3 consecutive full-suite runs (both dev and m1-dev presets build clean); test_vad_ptt_devices passed 5 consecutive standalone runs; manually verified live (vccli --list-devices against real hardware, vccli --voice --input-mode vad streaming without incident). Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
94 lines
7.4 KiB
Markdown
94 lines
7.4 KiB
Markdown
# Tech Stack & Dependencies
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Concrete library choices with versions and rationale. Everything in the **core** is C++
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(C++20). UIs are Swift and C#. Build is CMake + vcpkg.
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## 1. Core library (`libvoicecat`, C++20)
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| Concern | Choice | Version (as of 2026-06) | Why / notes |
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|---------|--------|-------------------------|-------------|
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| Sockets, timers, async | **Standalone Asio** | 1.30.x | Header-only, no Boost dependency, cross-platform TCP+UDP+timers, one reactor for client and server. (Boost.Asio is interchangeable if we already pull Boost.) |
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| TLS 1.3 (control) | **mbedTLS 3.6 LTS** | 3.6.x (LTS ≥ Mar 2027) | **Apache-2.0** (permissive — clean for eventual closed-source distribution). TLS 1.3 client+server, plus `mbedtls_ssl_export_keying_material()` to seed the media AEAD. **Static-links cleanly → single self-host binary.** OpenSSL 3.x (Apache-2.0) is an interchangeable alternative. No DTLS/wolfSSL (GPL) — see [security.md](security.md) §2. |
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| Crypto primitives + password hashing + media AEAD | **libsodium** | 1.0.20 | **ISC.** Argon2id (`crypto_pwhash`), ChaCha20-Poly1305 (per-frame media encryption), Ed25519 server identity, X25519, CSPRNG. Audited, hard to misuse. |
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| Audio codec | **libopus** | **1.6** (2025-12) | Per-channel mono/stereo, bitrate, frame size; in-band FEC, DTX, PLC, and optional **DRED** deep redundancy; Opus HD/96 kHz available. The whole reason the design is codec-flexible. |
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| Audio capture/playback | **miniaudio** | 0.11.x | Single-header, public-domain, backends for **WASAPI / CoreAudio / ALSA / PulseAudio**. One real-time abstraction across all desktop targets; keeps the RT path identical. |
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| Audio DSP — AEC/NS/AGC/VAD | **webrtc-audio-processing** (APM) — **planned, not built** | 1.x (standalone APM) | **BSD-3**, but has no working Windows/MSVC build upstream (GCC-only Meson, MinGW support unfinished, hard `abseil-cpp` dep — see roadmap.md §2). v1 ships a lightweight, dependency-free energy/RMS VAD instead (`core/src/audio/apm_processor.cpp`); there is **no AEC, NS, or AGC implementation at all** yet. Real APM stays a tracked future swap behind the same `ApmProcessor` interface. |
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| Resampling + jitter ref | **speexdsp** | 1.2.x | BSD. Resampler for non-48 kHz devices; lightweight jitter-buffer reference. (No longer the NS/AGC/VAD source — APM replaces it.) |
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| Control serialization | **Protocol Buffers** (protobuf-lite) | 5.x (proto3) | Codegen for C++/C#/Swift; additive, forward/backward compatible; `oneof` envelopes. `nanopb` is a fallback if footprint matters. |
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| Server persistence | **SQLite** | 3.4x | Accounts, channels, bans, config. Zero-admin, single file, ships everywhere. |
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| Logging | **spdlog** | 1.14.x | Fast, async-capable; off the RT path. |
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Resampling note: Opus runs internally at 48 kHz; miniaudio can deliver 48 kHz directly, so
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explicit resampling (speexdsp/libsamplerate) is only needed when a device can't do 48 kHz.
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## 2. Clients
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### macOS / iOS — Swift
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| Concern | Choice | Notes |
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|---------|--------|-------|
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| Language | **Swift 5.9+** | Direct **Swift↔C++ interop** available, but we bind through the C ABI for parity with Windows. |
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| UI | **SwiftUI** | Single UI codebase for macOS + iOS where practical; AppKit/UIKit shims as needed. |
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| Audio session (iOS) | **AVAudioSession** | App owns category `.playAndRecord` + `.voiceChat` mode, mic permission, interruption/route-change handling; calls `vc_audio_suspend/resume` on the core. macOS uses CoreAudio via the core directly. |
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| Packaging | Swift Package + Xcode project | Core shipped as an XCFramework (device + simulator + macOS slices). |
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| Future | CallKit / PushKit | For background VoIP + incoming-call UX on iOS. Post-v1. |
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### Windows — C#
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| Concern | Choice | Notes |
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|---------|--------|-------|
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| Runtime | **.NET 8+** | LTS. |
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| Interop | **`LibraryImport`** (source-gen P/Invoke) over the C ABI | Marshal the event callback as a function pointer (`[UnmanagedCallersOnly]`) to avoid delegate-lifetime bugs; keep the interface "chunky" not "chatty" to minimize managed↔native transitions. |
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| UI | **WinUI 3** (most native) or **Avalonia** | WinUI for a first-class Windows look; Avalonia if we later want one C# UI across desktop OSes. |
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| Audio | handled by the core (miniaudio/WASAPI) | C# only drives device selection + meters. |
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## 3. Server (`voicecat-server`)
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- Pure C++ linking the core; **no GUI**. Runs on **Linux** (primary), **macOS**, **Windows**.
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- Config via a `server.toml` (`allow_guests`, ports, channel defaults, Opus policy, TLS cert
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paths or auto-self-signed + Ed25519 identity, Argon2id cost params, rate limits).
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- SQLite for state. Single process for v1; interfaces drawn so a multi-node build is
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*possible* later but explicitly out of scope.
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- Packaging: static-ish binary per OS; systemd unit + Docker image for Linux.
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## 4. Build & tooling
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| Tool | Use |
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|------|-----|
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| **CMake** (3.25+) | One build graph for core + server + test CLI; UI projects consume the built core. |
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| **vcpkg** (manifest mode) | Pin C/C++ deps (opus, libsodium, mbedtls, protobuf, sqlite3, spdlog, asio, miniaudio — see `vcpkg.json`). `webrtc-audio-processing`/`speexdsp` are **not** in the manifest: no working vcpkg port / no working Windows/MSVC build exists upstream for the former; the latter was never actually wired up (the lightweight VAD needs no resampler). Reproducible across OSes. |
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| **protoc** | Generate C++/C#/Swift from `core/proto/*.proto` (single source of truth). |
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| **clang-format / clang-tidy** | Style + static analysis on the core. |
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| **CTest + a fuzz target** | Unit/integration tests; fuzz the frame parser and protobuf boundary (security-sensitive). |
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| **GitHub Actions** (or similar) | Matrix CI: Linux/macOS/Windows core+server; Xcode build for Apple; `dotnet` build for Windows. |
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## 5. Licensing — permissive only (hard rule)
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The code will eventually be distributed in **closed-source** form, so **no GPL/LGPL
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dependencies are permitted.** Every dependency below is BSD / MIT / ISC / Apache-2.0 /
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public-domain:
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- **mbedTLS** — Apache-2.0 ✅ · **libsodium** — ISC ✅ · **libopus** — BSD ✅ ·
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**miniaudio** — public domain / MIT-0 ✅ · **protobuf** — BSD ✅ ·
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**SQLite** — public domain ✅ · **Asio** (standalone) — Boost ✅ · **spdlog** — MIT ✅.
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**webrtc-audio-processing** would be BSD-3 ✅ if/when it's actually built in (see §1) —
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not a live dependency today, so not part of the resolved vcpkg graph the license scanner
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below checks.
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- **Explicitly rejected:** **wolfSSL** (GPLv2/commercial) and any DTLS stack that would drag
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in copyleft. The exported-keys + AEAD media design (security.md §2) removes the need for
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one entirely.
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- CI runs a license scanner over the resolved vcpkg graph and **fails the build on any
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GPL/LGPL transitive dependency**, so this rule can't silently regress.
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## 6. Why not the obvious alternatives
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- **WebRTC** — explicitly rejected: ICE/SDP/TURN complexity, huge dependency, opaque. We
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want plain TCP+UDP we fully control.
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- **QUIC** — capable (reliable streams + datagrams + TLS 1.3 in one), but heavier and drifts
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toward the complexity we're avoiding. Revisit only if NAT traversal/multiplexing pain
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appears.
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- **gRPC** for control — pulls HTTP/2 and a lot of surface for what is a simple framed
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message stream over TLS. Plain protobuf-over-framed-TLS is enough.
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- **A Rust core** — viable and memory-safe, but the user prefers C++ and the Swift/C#
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binding story is marginally simpler from C++ (Swift can even consume C++ directly).
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