DVD-Audio is a format for delivering high-fidelity audio content on a DVD. It offers many channels (from mono to 5.1 surround sound) at various sampling frequencies and sample rates. Compared to the CD format, the much higher capacity DVD format enables the inclusion of either considerably more music (with respect to total running time and quantity of songs) or far higher audio quality (reflected by higher linear sampling rates and higher vertical bit-rates, and/or additional channels for spatial sound reproduction).
Audio on a disc can be 16, 20 or 24 bit, with sampling rates of 44.1, 48, 88.2, 96, 176.4 or 192 kHz. (The highest sampling rates of 176.4 and 192 kHz are limited to two channels.) Different sampling sizes and frequencies can be used on a single disc. Audio is stored on the disc in LPCM format (uncompressed or losslessly compressed with Meridian Lossless Packing). The DVD-Audio player may downmix surround sound to two-channel stereo if the listener does not have a surround sound setup. The downmix capability is limited to two-channel stereo, not to other configurations, such as 4.1. DVD-Audio may also feature menus, text subtitles, still images and slideshows. Inclusion of DVD-Video also is possible. Such discs commonly contain Dolby Digital or DTS versions of the audio (with lossy compression, usually downsampled to lower sampling sizes and frequencies) in the DVD-Video section. This is done to ensure compatibility with DVD-Video players.
A "hybrid" DVD-Audio disc (HDAD) contains a standard audio track (e.g., 24 bit/96 kHz) on one side, playable on any DVD-Video player. The other side contains the same content with a higher sampling rate, such as 24 bit/192 kHz, playable only on a compatible DVD-Audio player. High fidelity DVD-Audio is normally not output in digital format by DVD-Audio players, to discourage digital copying. One notable exception is the British high end company Meridian, who as co-inventor of the format is allowed to transfer digitally from source to their "digital" loudspeakers (i.e. active speakers with SPDIF inputs and digital-analogue conversion on board) via a proprietary, encrypted link. DVD-Audio players have six analog outputs, one for each audio channel (left, right, center, left surround, right surround, and Subwoofer). DVD-Audio players require a compatible Surround sound amplifier, with the same six analog inputs, to play program material in surround. Otherwise, it is quite possible to use the format to play stereo recordings at high resolution with an ordinary stereo amplifier.