voice-subsystem-keeper

Development

Work with DiscordPHP's voice subsystem — voice gateway protocol opcodes, encryption (VoiceGroupCrypto), voice packets, audio streaming, and Discord.php voice integration. Use when touching Voice/*, joinVoiceChannel, or voice encryption/packet logic.

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Skill: voice-subsystem-keeper

Use this skill when work touches src/Discord/Voice/*, Discord::joinVoiceChannel(), voice event handlers in Discord.php, or anything involving audio encryption and packets.

Architecture overview

Voice support is split across three locations. Understand the boundary before touching any of them:

Location	What lives here
`src/Discord/Voice/*`	Internal protocol types: opcodes (Hello, Ready, Speaking), session description, voice packets, encryption classes and traits. These are pure data/crypto — no audio I/O.
`src/Discord/Discord.php`	Runtime integration: `joinVoiceChannel()`, voice state update handlers, voice server update handlers. This is where the external voice client is wired to gateway events.
`discord-php-helpers/voice` (external package)	`Manager` and `VoiceClient`: actual audio I/O, Opus encoding, UDP transport, stream management. DiscordPHP delegates audio work here.

Rule: do not blur these boundaries. Protocol types belong in Voice/*, audio I/O belongs in the external package, and wiring belongs in Discord.php.

Read in this order

src/Discord/Voice/VoiceGroupCrypto.php — encryption/decryption base class
src/Discord/Voice/VoiceGroupCryptoTrait.php — mixin providing group-based AEAD crypto
src/Discord/Voice/VoiceGroupCryptoInterface.php — contract
src/Discord/Voice/VoicePacket.php — encrypted RTP packet encapsulation
src/Discord/Voice/SessionDescription.php — session key and mode negotiation
src/Discord/Voice/Speaking.php, src/Discord/Voice/Hello.php, src/Discord/Voice/Ready.php, src/Discord/Voice/Resumed.php — voice gateway opcodes
src/Discord/Voice/Platform.php, src/Discord/Voice/Region.php — enum helpers
src/Discord/Discord.php — search for joinVoiceChannel, VOICE_STATE_UPDATE, VOICE_SERVER_UPDATE
src/Discord/Helpers/Buffer.php — writable stream for audio buffering (extends EventEmitter)

Core concepts

Voice gateway protocol

Discord voice uses a separate WebSocket gateway from the main gateway. The handshake sequence is:

Hello — server sends heartbeat interval
Identify — client sends token + session
Ready — server sends UDP endpoint + SSRC
Select Protocol — client sends chosen encryption mode
Session Description — server sends secret key
Speaking — sent before/after transmitting audio

The classes in src/Discord/Voice/ model these protocol steps as typed value objects.

Encryption

VoiceGroupCrypto provides AEAD encryption for RTP packets. It depends on libsodium (ext-sodium). The trait VoiceGroupCryptoTrait provides the implementation; concrete classes select the cipher mode (e.g., aead_xchacha20poly1305_ietf).

LibSodiumNotFoundException is thrown at runtime if the extension is absent — do not suppress it
Cipher mode is negotiated via SessionDescription

VoicePacket

VoicePacket encapsulates an encrypted RTP packet:

SSRC identifies the audio source
Sequence number and timestamp are required for RTP ordering
The packet is encrypted before transmission using the session secret key

Audio I/O (external package)

discord-php-helpers/voice owns all audio work:

Opus codec encoding/decoding
UDP socket management
OGG/Opus stream handling
FFmpeg process integration

Do not replicate any of this in src/Discord/Voice/. If you need to add audio capability, contribute to the external package or wrap it.

Old* files

OldVoiceClient.php, OldBuffer.php, OldOggStream.php, OldOggPage.php, OldOpusHead.php, OldOpusTags.php, OldReceiveStream.php are legacy implementations. They are preserved for compatibility only.

Do not extend, copy patterns from, or add new features to any Old* class. Fix bugs in them only when the fix is isolated and does not require architectural change.

Companion surfaces

When touching voice code, also inspect:

Touching	Also inspect
`VoiceGroupCrypto` or crypto mode	`SessionDescription`, `VoicePacket`, `VoiceGroupCryptoInterface`, `LibSodiumNotFoundException`
`Speaking` or voice gateway opcode	`Hello`, `Ready`, `Resumed`, `SessionDescription` — full handshake chain
`Discord.php` voice handlers	Voice gateway opcodes, `Buffer`, external voice package `Manager`
`Buffer.php`	`Multipart.php` (similar streaming pattern), external voice package stream classes
Any new voice encryption mode	`VoiceGroupCryptoInterface`, crypto trait, `SessionDescription` mode list

Playbook: adding a new voice encryption mode

Add the mode constant to SessionDescription.
Implement the mode in a class using VoiceGroupCryptoTrait or extending VoiceGroupCrypto.
Register the mode in the external voice package's cipher negotiation if needed.
Update VoiceGroupCryptoInterface if the contract changes.
Verify libsodium function availability — throw LibSodiumNotFoundException if missing.
Add tests for encrypt/decrypt round-trip.

Playbook: adding a voice gateway opcode

Create a typed value class under src/Discord/Voice/ mirroring the Discord voice gateway docs.
Wire the opcode handler in Discord.php (find the voice WebSocket message handler).
Document the opcode sequence in the class docblock.
Do not put audio I/O logic in the opcode class — keep it as a typed payload.

Design tripwires

Adding audio codec, UDP, or FFmpeg logic inside src/Discord/Voice/ — that belongs in the external voice package
Extending any Old* class for new features
Skipping libsodium availability check before using sodium functions
Hard-coding a cipher mode instead of reading it from SessionDescription
Blocking I/O inside voice packet or stream handlers — everything must be async/Promise-based
Catching LibSodiumNotFoundException silently instead of surfacing it to the caller

Reference files

src/Discord/Voice/VoiceGroupCrypto.php — encryption base
src/Discord/Voice/VoicePacket.php — RTP packet wrapper
src/Discord/Voice/SessionDescription.php — session key/mode
src/Discord/Voice/Speaking.php — voice speaking opcode
src/Discord/Helpers/Buffer.php — writable stream helper
src/Discord/Exceptions/LibSodiumNotFoundException.php — crypto dependency guard
src/Discord/Exceptions/OpusNotFoundException.php — codec dependency guard
src/Discord/Exceptions/FFmpegNotFoundException.php — audio tool dependency guard