How a Bluetooth Headset Works
Before discussing the limitations of the Bluetooth headsets, it is important to understand how today's Bluetooth headsets work.
As the diagram above shows, audio streams are handled by two separate profiles. One is called HFP (Hands-Free Profile) and is used for communication audio (e.g., video conferencing, interactive gaming). This profile provides bidirectional audio channels (speaker and microphone). But they are monaural, and their quality is not so good.
The other, called A2DP (Advanced Audio Distribution Profile), can handle stereo audio with good sound quality. But it supports only one direction.
Bluetooth Headset Limitations
In theory, these two profiles are independent and can be used simultaneously. But, in reality, most, if not all, Bluetooth headsets on the market today do not support the simultaneous use of the HFP and A2DP profiles. There is a "switch" (the part highlighted with a yellow box) in the headset, and it only plays the sound from one of them (it is a "switch", not a "mixer").
As a result, the following limitations apply regardless of which driver/OS you are using:
- To use the microphone, you have to send the playback audio through the HFP profile (using the "Headset Speaker" endpoint), and the audio will be monaural.
If you try to send data through the A2DP profile while the microphone is in use (i.e., HFP is active), the data may be sent to the headset, but the headset will ignore it.
- To hear the stereo audio, you have to send the data via A2DP (using the "Headphone Speaker" endpoint). And you have to make sure that no other application is using the "Headset Speaker" and "Headset Microphone" endpoints.
Starting with version 1.2.0, the Alternative A2DP Driver configuration app displays the following message in the Current Status section.
If you see this message, it means that HFP is active because:
- One of the running applications accessed the microphone of the headset, or
- One of the running applications opened the "Headset Speaker" endpoint.
And as a result:
- You hear a low-quality monaural sound, and
- You do not hear the sound streamed to the "Headphones Speaker" endpoint.
Windows 11 "Unified Audio Endpoint" Feature
Confused? You are not alone. Many people have had trouble in configuring the video conferencing programs properly, and Windows 11 has come up with a solution called "Unified Audio Endpoint". Instead of exposing two playback endpoints ("Headphones Speaker" and "Headset Speaker"), it exposes only one unified "Speaker" endpoint to the user. It then dynamically redirects the stream to either the "Headphone Speaker" or "Headset Speaker" endpoint, depending on the state of HFP.
This relieves the user of the burden of selecting the correct endpoint. But don't forget that the underlying limitation is still there. When using the microphone, you are still forced to use a monaural speaker, and the sound quality is not good. This is a hardware limitation and cannot be solved by software.