Linux "VBI proxy"
With "video4linux" drivers only one application at a time can capture
VBI data. The 2nd generation "v4l2" API allows multiple clients to
open a device, but still only one client may read from the device. If
for example the Nxtvepg daemon runs in the background users will not be
able to start a Teletext application. The VBI proxy was developed as a
solution to this problem.