Bluetooth audio technology has made significant advancements over the past few decades and is widely used in various consumer electronic devices. Codec offloading, an important technology in modern Bluetooth audio devices, is becoming increasingly popular. It enhances device performance and efficiency by shifting the computational tasks of audio encoding and decoding from the main processor (CPU) to dedicated hardware components or coprocessors.
The RTL8761C is a highly integrated single-chip Bluetooth 5.3 controller that combines the Bluetooth protocol stack (LM, LL, LE), baseband modem, and RF module into one unit. It connects with the main processor via UART/USB and I2S/PCM interfaces to transmit Bluetooth HCI packets and audio data. Additionally, it integrates multiple audio codecs to meet the needs of various scenarios.
The RTL8761C supports codec offloading technology, which enhances the fluidity and speed of audio processing, ensuring stable transmission and reduced latency. This provides significant advantages for applications requiring real-time responsiveness and high-definition audio streaming.
The Host interacts with the RTL8761C for HCI signaling via the HCI interface to establish an eSCO or ISO link. Once the link is established, the Host exchanges audio data with the RTL8761C through the PCM/I2S interface. The RTL8761C encodes the audio data received from the Host and transmits the encoded data wirelessly. Simultaneously, the RTL8761C receives data from the air, decodes it, and then transmits the decoded data to the Host via the PCM/I2S interface.
In addition, the RTL8761C supports time-division multiplexing technology, allowing up to two eSCO links to share the same PCM interface. By dividing time slots, two audio streams can be transmitted over the same PCM channel. The chip is responsible for scheduling and time slot allocation to ensure stable audio quality and avoid conflicts. This method of time slot allocation effectively enhances the utilization of existing PCM channels and reduces the need for additional hardware resources.
To further optimize performance and energy efficiency, the RTL8761C integrates the LC3 codec specifically for LE Audio. It similarly supports time-division multiplexing, allowing two CIS links to share the same PCM interface for efficient audio transmission. This setup enhances audio performance while maintaining low power consumption, offering a balanced solution for high-quality audio streaming.
Here are two typical application scenarios:
In a car, the driver can connect two phone lines simultaneously and switch between them quickly. This feature allows for greater flexibility and convenience, especially during important calls, as it enables the driver to manage multiple conversations without needing to disconnect and reconnect each time. This setup can be particularly useful for business professionals or anyone who frequently handles calls while on the move.
On a motorcycle, the rider and the passenger can communicate using helmets connected to the onboard Bluetooth, allowing them to avoid external noise interference. This makes the riding experience safer and more comfortable, allowing them to communicate easily while on the move.
These designs make the RTL8761C an ideal choice for enhancing the performance and user experience of Bluetooth audio devices.
