Wave lab considers it downmixing:
Stereo Down Mixing
An important issue when creating DVD-Audio is stereo compatibility. Although surround playback devices are becoming more and more common, there are still many occasions when playback is done in stereo - when using headphones, boomboxes or computer monitors, for example. To make a DVD-Audio playable in stereo, you could include two versions of each track, one in surround and one in stereo. The problem with this solution is that it requires more storage space on the disc - there will be room for less music.

An alternative solution is to use Stereo Down Mixing tables. This means that you can specify how each surround channel should be represented in the stereo mix by supplying gain coefficients. When the DVD-Audio is played back on stereo equipment, the surround channels are combined to stereo - but they are "mixed" according to the coefficients you have specified. The left and right front signals are sent to the left and right channel respectively, with a slight attenuation.
- The center signal is sent in equal amounts to the left and right channel.
- The left and right surround (rear) signals are more heavily attenuated and sent to the left and right channel respectively.
- The LFE signal is not included at all in the down mix.