pw-splitter

A TUI application for PipeWire that lets you capture audio from an application at full volume for recording while independently controlling your local listening volume.

The Problem

When you're recording or streaming with OBS, you often want to:

• Send game/application audio to OBS at full volume for a clean recording
• Listen to that same audio locally at a lower volume so it doesn't blast your ears
  • e.g. You want people talking to be louder than game.

In PipeWire, adjusting an application's volume affects all destinations. If you turn down a game's volume to save your hearing, your recording also gets quieter.

The Solution

pw-splitter creates two parallel audio paths from your source application - one to your recording software at full volume, and one to your speakers with adjustable volume.

BEFORE (volume affects everything):

    [Game Audio] ──────────────────────────────> [Speakers]
         │                                        (loud!)
         │
         └─────────────────────────────────────> [OBS Recording]
                                                  (also loud!)

    Turning down the game makes BOTH quieter.

AFTER (independent volume control):

    [Game Audio] ───┬──> [To Recording] ──> [OBS Mic/Aux]
                    │     (full volume)
                    │
                    └──> [To Local] ──> [Speakers]
                          (adjustable)

    Adjust "To Local" volume in pwvucontrol - recording stays at 100%.

Installation

First, check your package manager (e.g., dnf install pw-splitter, pacman -S pw-splitter) for a pre-packaged version.

From GitHub Releases (Recommended)

Download the latest release from GitHub Releases. Pre-built binaries are available for:

• linux-x64.zip (x86_64)
• linux-x86.zip (i686)
• linux-arm64.zip (aarch64)

# Download and run (example for x86_64)
wget https://github.com/Sewer56/pw-splitter/releases/latest/download/linux-x64.zip
unzip linux-x64.zip
chmod +x pw-splitter
./pw-splitter

From crates.io

If you have Rust installed, install from crates.io:

cargo install pw-splitter

Quick Start

# Move to source directory
cd src

# Build and run the project
cargo run --release

# Use arrow keys to select:
#   1. Source application (e.g., "Dolphin Emulator")
#   2. Recording destination (e.g., "OBS [Mic/Aux]")
#   3. Press Enter to confirm

# Adjust local volume in pwvucontrol
# Look for the loopback with "Local" in the name

Usage

Interactive Mode (TUI)

pw-splitter

Command Line

pw-splitter list        # Show active splits
pw-splitter stop <name> # Stop a specific split
pw-splitter stop-all    # Stop all splits

How It Looks in qpwgraph

After setting up a split for Dolphin Emulator to OBS [Mic/Aux]:

┌────────────────────────────────────────────┐
│ Dolphin Emulator [Dolphin Audio Output]    │  ◄── Source application
└──────────┬─────────────────────┬───────────┘
           │                     │
           ▼                     ▼
┌────────────────────┐    ┌────────────────────┐
│ Dolphin Emulator   │    │ Dolphin Emulator   │
│ -> Local           │    │ -> OBS             │
│ [...Local input]   │    │ [...OBS input]     │  ◄── Loopback capture sides
└─────────┬──────────┘    └──────────┬─────────┘
          │                          │
          ▼                          ▼
┌────────────────────┐    ┌────────────────────┐
│ Dolphin Emulator   │    │ Dolphin Emulator   │
│ -> Local           │    │ -> OBS             │
│ [...Local output]  │    │ [...OBS output]    │  ◄── Loopback playback sides
└─────────┬──────────┘    └──────────┬─────────┘
          │                          │
          ▼                          ▼
┌────────────────────┐    ┌────────────────────┐
│ USB Audio Speakers │    │ OBS-1 [Mic/Aux]    │
└────────────────────┘    └────────────────────┘

Nodes created by pw-splitter:

To adjust local volume:

In pwvucontrol or qpwgraph, find the loopback with "Local" in the name and adjust its volume. The recording to OBS will stay at 100% regardless of this setting.

Technical Details

PipeWire Terminology

Architecture

The split works by creating two pw-loopback instances that both capture from the source application:

┌──────────────┐     ┌─────────────────┐     ┌──────────────┐
│    Source    │     │  pw-loopback    │     │   Speakers   │
│  Application │────▶│  (to Local)     │────▶│              │
│              │     │  [adjustable]   │     │              │
│              │     └─────────────────┘     └──────────────┘
│              │
│              │     ┌─────────────────┐     ┌──────────────┐
│              │     │  pw-loopback    │     │     OBS      │
│              │────▶│  (to Recording) │────▶│  [Mic/Aux]   │
│              │     │  [full volume]  │     │              │
└──────────────┘     └─────────────────┘     └──────────────┘

Step-by-Step Process

1. Create two loopbacks with node.autoconnect=false on both capture and playback sides:

   # Recording loopback (to OBS)
   pw-loopback \
     --capture-props='media.class=Audio/Sink node.name=MyApp_to_Recording node.description="MyApp -> OBS" node.autoconnect=false stream.capture.sink=true' \
     --playback-props='media.class=Stream/Output/Audio node.name=MyApp_to_Recording node.description="MyApp -> OBS" node.autoconnect=false'
   
   # Local loopback (to speakers)
   pw-loopback \
     --capture-props='media.class=Audio/Sink node.name=MyApp_to_Local node.description="MyApp -> Local" node.autoconnect=false stream.capture.sink=true' \
     --playback-props='media.class=Stream/Output/Audio node.name=MyApp_to_Local node.description="MyApp -> Local" node.autoconnect=false'
   

   Key options:

   • node.autoconnect=false - Prevents PipeWire from auto-connecting
   • stream.capture.sink=true - Captures from sinks (apps), not sources (mics)

2. Disconnect source from original outputs:

   # Remove existing links to speakers
   pw-link -d "Dolphin Emulator:output_FL" "speakers:playback_FL"
   pw-link -d "Dolphin Emulator:output_FR" "speakers:playback_FR"
   
   # Also remove any existing links to the recording destination
   pw-link -d "Dolphin Emulator:output_FL" "OBS:input_FL"
   pw-link -d "Dolphin Emulator:output_FR" "OBS:input_FR"
   

3. Connect source to both loopback capture inputs:

   # Source → Recording loopback capture
   pw-link "Dolphin Emulator:output_FL" "MyApp_to_Recording:input_FL"
   pw-link "Dolphin Emulator:output_FR" "MyApp_to_Recording:input_FR"
   
   # Source → Local loopback capture
   pw-link "Dolphin Emulator:output_FL" "MyApp_to_Local:input_FL"
   pw-link "Dolphin Emulator:output_FR" "MyApp_to_Local:input_FR"
   

4. Connect loopback playback outputs to destinations:

   # Recording loopback → OBS input (using port IDs to avoid node name ambiguity)
   pw-link 85 118   # port ID 85 = loopback output_FL, port ID 118 = OBS input_FL
   pw-link 86 119   # port ID 86 = loopback output_FR, port ID 119 = OBS input_FR
   
   # Local loopback → Speakers (can use names since speakers have unique names)
   pw-link "MyApp_to_Local:output_FL" "speakers:playback_FL"
   pw-link "MyApp_to_Local:output_FR" "speakers:playback_FR"
   

   Note: Port IDs are used for OBS because multiple OBS inputs share node.name="OBS", making port names like OBS:input_FL ambiguous.

Why Manual Linking for OBS?

OBS audio inputs are Stream/Input/Audio nodes - they're capture streams that read FROM sinks, not sinks themselves. You can't target them with pw-loopback's target.object on the playback side.

Additionally, multiple OBS inputs share the same node.name ("OBS"), making port names like OBS:input_FL ambiguous. We use port IDs directly to ensure we connect to the correct OBS input.

State Management

Active splits are stored in /tmp/pw-splitter/<name>.json:

{
  "name": "DolphinEmulator_Split",
  "source_node_id": 158,
  "recording_loopback_name": "DolphinEmulator_to_Recording",
  "local_loopback_name": "DolphinEmulator_to_Local",
  "recording_dest_node_id": 118,
  "loopback_to_recording_pid": 12345,
  "loopback_to_local_pid": 12346,
  "original_links": [
    {"output_port": "Dolphin Emulator:output_FL", "input_port": "speakers:playback_FL"}
  ]
}

This enables:

• Listing active splits
• Proper cleanup (kill processes, restore original links)
• Auto-restart of crashed loopback processes

Cleanup Process

When stopping a split:

1. Kill both pw-loopback processes
2. Restore original audio links
3. Delete the state file

Building

cargo build --release

Dependencies:

• ratatui - TUI framework
• crossterm - Terminal handling
• serde / serde_json - State serialization
• argh - CLI parsing
• thiserror - Error handling

Runtime requirements:

• PipeWire
• pw-link, pw-loopback, pw-dump commands

License

MIT

I needed something easy to use for a one-off stream; and maybe future use. Given that an LLM did most of the heavy lifting, I'd rather release this for absolutely free.

Developer Manual

For step-by-step development guidance, see the Developer Manual.

Contributing

We welcome contributions! See the Contributing Guide for details.