The DVB audio device controls the MPEG2 audio decoder of the DVB hardware. It can be accessed through /dev/dvb/adapter?/audio?. Data types and and ioctl definitions can be accessed by including linux/dvb/audio.h in your application.
Please note that some DVB cards don’t have their own MPEG decoder, which results in the omission of the audio and video device.
These ioctls were also used by V4L2 to control MPEG decoders implemented in V4L2. The use of these ioctls for that purpose has been made obsolete and proper V4L2 ioctls or controls have been created to replace that functionality.