gmcl_voice_packets

A Garry's Mod client-side module that captures voice chat data, decompresses it, and saves it as WAV files. It also provides a Lua API to monitor and handle voice activity.

Compatibility

Important

This module is now optimized for the 64-bit (x86-64) version of Garry's Mod. While 32-bit build configurations exist, they are considered legacy/non-functional because the engine offsets are maintained exclusively for the x64 architecture.

Tested with:

• Protocol version: 24
• Network version: 2025.03.26 (garrysmod)
• Exe build: 14:35:20 Apr 1 2026 (10007) (4000)
• GMod version: 2026.04.01, branch: x86-64, multicore: 1
• Windows 64-bit

Build Instructions

Prerequisites

• Premake5 (Included in root)
• garrysmod_common

Step-by-Step Setup

1. Initialize Environment: Run generate_garrysmod_common.bat. This ensures all necessary headers from garrysmod_common are initialized.
2. Generate Projects: Run generate_x64.bat. This uses premake5_x64.lua to create the Visual Studio solution.
3. Open Solution: Navigate to projects\windows\vs2026\x64 and open voice_packets.slnx.
4. Compilation:
   • Set configuration to Release and platform to x64.
   • Press F7 to build the solution.
5. Output: The binary gmcl_voice_packets_win64.dll will be created in the output directory.

Maintenance & Offsets

Tip

This module no longer requires manual offset updates after game patches.

The module implements an internal Pattern Scanner that searches the engine.dll memory space for the specific instruction signature of SVC_VoiceData::Read. This ensures that the module remains functional even if the function's memory address changes in future Garry's Mod updates.

Lua API Documentation

Methods (voice_packets table)

voice_packets.SetTimeout(number: seconds)

Sets the duration of silence required before a voice session is considered "finished."

• Default: 1.0
• Example: voice_packets.SetTimeout(0.5)

voice_packets.GetActiveSpeakers()

Returns a sequentially indexed table of player indices (UserIDs) currently transmitting voice.

• Returns: table (e.g., {1, 4, 12})

voice_packets.CreateWavFromPCM(string: pcmData)

Converts raw 16-bit PCM data into a valid, playable .wav file string (48000Hz, Mono, 16-bit).

• Returns: string (Binary WAV data)

voice_packets.CheckVoiceTimeouts()

Internal logic handler. This is called automatically by a module-created timer every 0.1s to trigger OnVoiceChatEnd.

---

Hooks

OnVoiceChatStart(number: clientIndex)

Called the moment the module detects the first voice packet from a specific player.

• clientIndex: The Entity index of the player.

OnVoiceChatEnd(number: clientIndex, string: pcmData)

Called when a player stops talking (after the timeout duration).

• clientIndex: The Entity index of the player.
• pcmData: The raw, decompressed 16-bit PCM binary string. Use CreateWavFromPCM to save this as a file.

Example Usage

local status = pcall(require, "voice_packets")

if not status or not voice_packets or not voice_packets.CheckVoiceTimeouts then
    print("[Voice-Lua] ERROR: C++ library not loaded!")
    return
end

local pathDir = "voice_logs"
if not file.Exists(pathDir, "DATA") then
    file.CreateDir(pathDir)
end

voice_packets.SetTimeout(1.0)

timer.Create("CheckActiveSpeakers", 5, 0, function()
    local active = voice_packets.GetActiveSpeakers()

    if #active > 0 then
        local names = {}
        for _, idx in ipairs(active) do
            local ply = Entity(idx)
            table.insert(names, IsValid(ply) and ply:Nick() or "Player " .. idx)
        end
        print("[Voice] Currently speaking: " .. table.concat(names, ", "))
    end
end)

hook.Add("OnVoiceChatStart", "MyVoiceStart", function(clientIndex)
    local ply = Entity(clientIndex)
    local name = IsValid(ply) and ply:Nick() or "Player " .. clientIndex
    print("[Voice] " .. name .. " started speaking...")
end)

hook.Add("OnVoiceChatEnd", "MyVoiceEnd", function(clientIndex, data)
    if not data or #data == 0 then return end

    local wav = voice_packets.CreateWavFromPCM(data)
    local ply = Entity(clientIndex)
    
    local rawName = IsValid(ply) and ply:Nick() or "unknown_" .. clientIndex
    local safeName = string.gsub(rawName, "[%c%/%\\%:%*%?%\"%<%>%|]", "_")
    
    local fileName = "voice_" .. safeName .. "_" .. os.time() .. ".wav"
    local filePath = pathDir .. "/" .. fileName

    file.Write(filePath, wav)

    local sizeKB = #wav / 1024
    print(string.format("[Voice] Recording saved: %s | Size: %.2f KB", fileName, sizeKB))
end)

How It Works

The module hooks the SVC_VoiceData::Read method inside engine.dll using MinHook.

1. Extraction: It intercepts the raw bitstream from the engine.
2. Alignment: Manually aligns the bit-level data into byte-aligned buffers.
3. Decompression: Uses the Steamworks SDK (ISteamUser::DecompressVoice) to decode Opus/SILK data into standard 16-bit PCM.
4. WAV Construction: Adds the standard RIFF/WAVE headers to the PCM data upon request.

Notes

• The module is client-side only.
• It requires engine.dll offsets to be accurate.
• 64-bit GMod is mandatory for current build stability.