Audio
The CX2388x audio stream (Function 1) provides 48KHz, 16-bit stereo PCM audio from an analog TV or FM radio frontend, or from an external audio decoder via an I2S-compliant digital interface. The ioctl(2) interface for the cx88audio driver is defined in /usr/local/include/cx88/cx88_audio_ioctl.h, and is similiar to the interfaces for the MPEG TS and Raw Video drivers. The CX88_AUDIO_FORMAT ioctl is used to specify the broadcast format and/or input source of the audio data, but it does not need to be issued before the audio buffers are configured. If the CX88_AUDIO_FORMAT ioctl is not issued, the driver will default to using an FM radio format with an analog broadcast source.
OSS Interface
In addition to providing a "normal" cx88-style configuration/capture interface, the audio driver also integrates with FreeBSD's "pcm" audio driver framework, which allows it to be used as an OSS-compliant audio input device.