To obtain real-time responses with interactive multimedia servers, the
server provides at least two different audio/visual data streams. A first
data stream has fewer bits per frame and provides a video image much more
quickly than a second data stream with a higher number of bits and hence
higher quality video image. The first data stream becomes available to a
client much faster and may be more quickly displayed on demand while the
second data stream is sent to improve the quality as soon as the playback
buffer can handle it. In one embodiment, an entire video signal is
layered, with a base layer providing the first signal and further
enhancement layers comprising the second. The base layer may be actual
image frames or just the audio portion of a video stream. The first and
second streams are gradually combined in a manner such that the playback
buffer does not overflow or underflow.