Under the ideal condition (no transmission error/retransmission), Bluetooth can, theoretically, transmit up to ~1.5Mbps (assuming all time slots are filled with 2-DH5 packets) of the streaming data. But, in reality, radio signals are distorted by interference, and data needs to be retransmitted. As a result, the effective bitrate is much lower than that. If you are trying to use high-bitrate CODEC settings (such as SBC bitpool above 100, LDAC with HQ quality), you may need to pay attention to the following factors:
- Minimize radio interference to reduce the retransmission
Use high transmission power Bluetooth adapter
- Do not use 2.4GHz radio, such as 2.4GHz WiFi
Use 5/6GHz WiFi or wired Ethernet instead.
- If you have to use 2.4GHz WiFi, consider using a WiFi/Bluetooth combo adapter instead of separate adapters
WiFi and Bluetooth adapters communicate with each other and minimize interference in a combo adapter. They do not communicate with each other if you use separate adapters and cause more interference.
Bluetooth devices are classified into three power classes. Most Bluetooth adapters used for PC are either Class 1 (high power) or Class 2 (medium power). A Class 1 adapter gives you a more stable connection at a high bitrate. As of this writing, there is no easy way to tell if your adapter is Class 1 or Class 2, but here is a rule of thumb:
Maximize the time slot used by other Bluetooth devices
If you connect other Bluetooth devices, such as a keyboard, mouse, and touchpad, they eat up the time slots that can be used for audio streaming. The amount of data those devices send is relatively small, but their impact is not negligible as they send the data frequently.
Those devices may need to be turned off while high-bitrate audio streaming is happening to free up the time slots usable for audio streaming. (Or, if you use the high-bitrate audio streaming regularly, you may want to consider switching to the mouse/keyboard that uses non-Bluetooth wireless technologies.) Please note that those devices still consume timeslots while they are idle as long as they are connected to your PC.
TWS specific issues
Last but not least, TWS headphones are not good at receiving high-bitrate streams. You usually start hearing choppy sounds at a lower bitrate compared to regular headphones. This is because:
- Due to their smaller size, they don't have good antennas. It causes more data corruption and ends up with more re-transmission.
- Earbuds need to communicate with each other, and that is done using the Bluetooth time slots otherwise used to receive the streaming packets.
For example, LDAC HQ (990kbps) with TWS is not impossible, but for that to work without choppy noise, you need to clear all other issues listed above.