Abstract: Data to be transmitted over a network includes a first part (perhaps audio) which is always to be transmitted and alternative second parts (perhaps video coded at different compression rates) of which one is to be chosen for transmission, depending on the current network capacity. In order to accommodate systems where (owing perhaps to the use of a congestion control mechanism such as TCP) the capacity available is initially undetermined, one firstly begins to transmit just the first part. When the network capacity becomes known (typically by monitoring the performance of the network in transmitting the first part), one of the alternative second parts is chosen and transmission of it commences. If desired this may initially be preferentially to, or to the exclusion of, further transmission of the first part.

Abstract: Data to be transmitted over a network comprise a first part (perhaps audio) which is always to be transmitted and alternative second parts (perhaps video coded at different compression rates) of which one is to be chosen for transmission, depending on the current network capacity. In order to accommodate systems where (owing perhaps to the use of a congestion control mechanism such as TCP) the capacity available is initially undetermined, one firstly begins to transmit just the first part. When the network capacity becomes known (typically by monitoring the performance of the network in transmitting the first part), one of the alternative second parts is chosen and transmission of its commences. If desired this may initially be preferentially to, or to the exclusion of, further transmission of the first part.

Abstract: A data transmission method and system is disclosed in which one or more data streams are transmitted at respective transmission rates which are controlled to prevent data buffers in the receiver from overflowing. In some embodiments feedback data concerning the state of each buffer in a receiving client is received at the transmitting server, and used to adapt the sending rates to achieve the effect. Information indicative of the data decode rates or the fill extent of each buffer is communicated to the server as the feedback data. In other embodiments the server makes an open-loop estimate of the remaining space in the buffer, and controls the transmission rate accordingly. A data receiving method and system adapted to receive the data streams is also disclosed.