One aspect of the present invention discloses a network system capable of transmitting and processing audio video (“A/V”) data with enhanced quality of service (“QoS”). The network system includes a transmitter, a transmission channel, an adjustable decoder buffer, and a decoder. The transmitter contains an encoder able to encode A/V data in accordance with encoding bit rate recommendation from SQoS and packets loss notifications. The transmission channel, in one example, transmits A/V data from the transmitter or the receiver. The adjustable decoder buffer, in one aspect, is able to change its storage capacity or buffering size in response to the adaptive latency estimate. Upon fetching at least a portion of the A/V data from the adjustable decoder buffer, SQoS updates the adaptive latency estimate based on the quality of the decoded A/V data.