| 摘要 |
A method is provided that is performed by a client device such a set top box when a viewer requests a program by initiating a channel change from a program guide or entering a channel through the user interface. The client device receives the user request and, in response, the client device transmits the request to the streaming server in the headend, which causes the streaming server to create a unicast catch up stream that commences with a key frame. The streaming server calculates the end point of the catch up stream and continues to send the catch up stream at a rate faster than real time. The client device receives the catch up stream and begins buffering it. While the catch up stream is being buffered the client device begins decoding and presenting the content. The client device receives the end of stream marker, and in response, sends a request to join the multicast stream. Once the client device starts receiving the multicast stream, the client device discards any remaining images or pictures in the catch up stream that precede the synchronization time. The client device also begins to buffer the multicast stream as it continues to play the buffered catch up stream. When it reaches the end of the catch up stream, the client device begins to play out the buffered multicast stream.
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