[This is preliminary documentation and subject to change.]
Sound components can be laid out on a separate sound card or integrated elsewhere. If sound is laid out on a separate card, the television and MPEG sound from the video card must be connected to the sound card's line-in port, and this sound must be controlled with the standard mixer interface in Microsoft® Windows® operating systems. The video card selects the television-related sound that is heard by users, and the mixer controls the television volume.
For game support on a broadcast client, sound components compatible with SoundBlaster that provide wave table synthesis are recommended. The sound components must be capable of a signal-to-noise ratio of 90 decibels, to maintain the audio quality of the digital broadcast network. It must be possible to use the sound-card circuitry independent of the digital broadcast audio output — for example, when the user tape-records a program while playing a video game.
Although sound and video display components can be laid out on separate cards, achieving the highest possible sound quality usually requires a digital connection between the video display card and the sound card.
For compatibility with digital video disk (DVD) audio, an audio decoder with compression to the AC-3 algorithm is recommended.