Quality of Service Support for A/V Streams

An access control mechanism in a network connecting one or more sink devices to a server providing audio/visual data (A/V) in streams. As a sink device requests access, the server measures available bandwidth to the sink device. If the measurement of available bandwidth is completed before the sink device requests a stream of audio/visual data, the measured available bandwidth is used to set transmission parameters of the data stream in accordance with a Quality of Service (QoS) policy. If the measurement is not completed when the data stream is requested, the data stream is nonetheless transmitted. In this scenario, the data stream may be transmitted using parameters computed using a cached measurement of the available bandwidth to the sink device. If no cached measurement is available, the data stream is transmitted with a low priority until a measurement can be made. Once the measurement is available, the transmission parameters of the data stream are re-set. With this access control mechanism, A/V streams may be provided with low latency but with transmission parameters accurately set in accordance with the QoS policy.