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PipeWire Routing Tests – Multi-device Setup Trials
Introduction
In the world of audio on Linux, PipeWire has quickly emerged as a versatile and powerful tool for managing both audio and video streams. Initially designed to replace PulseAudio and JACK, PipeWire has proven itself to be a robust solution for handling complex audio routing scenarios, especially in multi-device setups. However, configuring and testing multi-device routing with PipeWire can sometimes be a complex and experimental process.
This post explores my experiences with PipeWire's multi-device routing capabilities, diving into various tests I conducted to better understand how the system manages audio across multiple devices. I’ll share insights, results, challenges, and some unexpected behaviors I encountered along the way. This is less of a step-by-step guide and more of an exploration of the process, intended to spark further curiosity for those wanting to dive deeper into PipeWire's potential.
1. The Power and Flexibility of PipeWire
1.1 What is PipeWire?
PipeWire is a media server that handles audio, video, and other multimedia data streams. Its design allows for a more unified approach to multimedia handling compared to previous solutions like PulseAudio (focused on audio) and JACK (focused on professional audio). PipeWire's main strength lies in its ability to provide low-latency audio processing, compatibility with professional audio tools, and flexibility in managing multiple devices simultaneously.
1.2 Multi-device Audio Routing
One of PipeWire's standout features is its ability to route audio between multiple devices seamlessly. This includes routing audio from one device to another (e.g., from a Bluetooth headset to a USB DAC or between two soundcards), combining multiple devices into a single output stream, or even creating virtual audio devices for more complex setups.
2. Setup: My Multi-device Configuration
For the purpose of these tests, I used the following devices:
- Internal Sound Card (Built-in): Used as the default system output.
- USB DAC: A high-fidelity external Digital-to-Analog Converter (DAC) for improved audio quality.
- Bluetooth Headset: For testing wirelessly paired devices.
- Virtual Audio Device: Configured to simulate a multi-channel setup for experimentation.
My primary goal was to test multi-device routing—specifically, how to output the same audio to multiple devices or route audio between them effectively. This is crucial for situations like:
- Playing different audio streams through separate outputs.
- Using external audio processing tools without interrupting the default system output.
- Redirecting specific audio applications to distinct devices.
3. Testing the Routing: The Process and Challenges
3.1 Test 1: Basic Audio Routing Between USB DAC and Internal Sound Card
The first test was relatively straightforward: route all system audio from the internal sound card to the USB DAC. This is a typical configuration for anyone wanting to prioritize sound quality from an external device.
- Expected Outcome: I expected the system to detect the USB DAC as the default output device and route all audio through it.
- Result: PipeWire handled this without issue. The DAC was picked up as the primary audio output, and audio routed through it seamlessly. The switch from internal audio to USB was instant with no noticeable latency or distortion.
3.2 Test 2: Simultaneous Output to USB DAC and Bluetooth Headset
Next, I wanted to test the simultaneous output of audio to both the USB DAC and the Bluetooth headset. This would simulate a setup where someone might want audio on both high-quality speakers and a wireless headset at the same time.
- Expected Outcome: Audio should be split, with one stream output to the DAC and the other to the Bluetooth headset.
- Result: Initially, PipeWire struggled with this configuration. The system would output audio to one device, but not both simultaneously. After some digging, I discovered that I needed to create a virtual audio device in PipeWire, which would combine the outputs of both devices into a single stream.
To achieve this:
- Create a virtual output using the
pw-clitool. - Map the devices (USB DAC and Bluetooth headset) to this virtual output using PipeWire’s routing capabilities.
- Adjust sink inputs to balance the audio levels between both devices.
After these adjustments, both devices received audio output, but there were noticeable sync issues. The Bluetooth headset had a slight delay compared to the DAC output, which is an inherent issue with Bluetooth audio latency. Nevertheless, the setup worked in principle, although the experience was not without compromise.
3.3 Test 3: Isolating Audio by Application
One of the more interesting use cases I wanted to explore was isolating audio by application—directing specific applications to specific outputs. For example, sending media playback through the DAC while routing system sounds through the internal sound card.
- Expected Outcome: PipeWire should allow individual audio applications to use specific output devices, while the system output remains separate.
- Result: This worked with minimal effort, thanks to PulseAudio compatibility within PipeWire. By using tools like pavucontrol (PulseAudio Volume Control) or Helvum (PipeWire’s graphical patchbay), I was able to assign applications to specific devices.
However, while this worked, I encountered some issues when switching devices. Sometimes, the system would forget the previous routing assignments, and I had to manually reconfigure the setup. While not a showstopper, this highlighted that PipeWire’s integration with other audio tools still has room for improvement, particularly for handling dynamic re-routing.
4. Lessons Learned and Observations
4.1 PipeWire's Strengths
- Flexibility: PipeWire’s ability to handle multiple devices simultaneously, both internally and externally, is impressive. It allows for fine-grained control over routing, which is essential for users who need custom audio setups.
- Low Latency: The system’s low-latency audio processing ensures that there is minimal delay between devices, which is crucial for professional audio work.
- Compatibility with PulseAudio Tools: PipeWire’s compatibility with PulseAudio utilities, such as
pavucontrolandpaprefs, makes it easy for users to adapt from older systems without learning entirely new tools.
4.2 Challenges and Areas for Improvement
- Bluetooth Audio Latency: Even with PipeWire’s capabilities, Bluetooth audio remains a challenge due to inherent latency. This is especially noticeable when routing to both wired and wireless devices simultaneously.
- Complexity of Multi-device Routing: While PipeWire is powerful, multi-device routing requires a fair amount of manual configuration. The need to create virtual devices and adjust sink inputs can be overwhelming for users without advanced knowledge of audio routing.
- Consistency: Some configurations, particularly when switching between devices or changing the system setup, can lead to temporary instability or forgotten device assignments. This requires additional troubleshooting and can disrupt the user experience.
5. Conclusion and Future Exploration
The tests conducted were an excellent learning experience, shedding light on PipeWire’s potential and limitations when it comes to managing multi-device audio routing. While the system offers great flexibility, it’s clear that fine-tuning is still required for the best results, especially when dealing with Bluetooth devices and dynamic configuration changes.
For future exploration, it would be interesting to experiment with more complex scenarios, such as routing specific audio streams to multiple devices with varying latency, or even integrating PipeWire with professional-grade software like Ardour for high-end audio production.
Overall, PipeWire is undoubtedly a powerful tool for those looking to push the boundaries of Linux audio routing, but it’s still evolving, and it requires a fair amount of experimentation and patience to get everything working perfectly.