In Figure 1B, without the fast switching technology, switching from the set-top box to the Blu-ray player can take up to ten seconds. During this interval, the user will see a blank blue screen. Figure 2 shows that a system without fast switching waits until the user selects the input on the remote control to switch from the set-top box to the Blu-ray player. The hot plug detect process initiated only upon user selection. The Blu-ray player then reads the DTV’s extended display identification data (EDID). Once the EDID content is read, the DTV begins the process of high-bandwidth digital content protection (HDCP) authentication with the Blu-ray player. This whole process can take up to ten seconds.
However, with fast switching, when the set-top box and Blu-ray player are initially connected to the DTV, the hot-plug detect signals of both HDMI inputs are recognized and the receiver terminations are activated on both inputs. The DTV provides the EDID information to both the set-top box and the Blu-ray player, and the HDCP authentication process is initiated for both. However, the DTV only authenticates HDCP for the selected device, which in Figure 1A is the set-top box. For the other, non-selected, device (Blu-ray player), the receiver will not acknowledge the TX HDCP bus and will fail the link authentication and link integrity check in the very last step of the HDCP authentication process. However, the non-selected input (Blu-ray player) has already completed most of the handshaking process, including obtaining EDID information from the DTV, and a large proportion of the HDCP authentication (such as determining DVI vs. HDMI, “content protection desired cycle” etc.) The non-selected input will now stay in the A0 state of the HDCP authentication process and will wait for the user to select it prior to completing the final A0 state. Then, when the user selects the Blu-ray player to be the active input on the DTV remote control, the user only has to wait for the final state of the HDCP authentication process to complete—which only takes about one second.