This type of input switching works with SCTE-35 messages that are in a transport stream source. When Elemental Live encounters an SCTE 35 message in the source, it sends the message to the POIS. The POIS might decide to send a request to switch input. Note that there is no sense of a particular type of SCTE 35 message that can trigger an input switch request. The POIS can request a switch in response to any type of SCTE 35 message that it receives.
Input types
SCTE-35-triggered input switching works only with the following sources:
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MPTS programs, from one MPTS input. MPTS programs are typically live sources.
Principle of operation
Elemental Live probes each non-active MPTS program for requests to switch to that non-active input. The request can be seen as a switch to this input. In addition, the originator of any potential action is Elemental Live.
Compare this principle of operation to asynchronous input switching, where the POIS sends a request to Elemental Live to request a switch away from the currently active input and to another input. The request can be seen as a switch away to another input. In addition, the originator of any potential action is the POIS.
Setup
In the event, you set up the inputs:
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You identify all the MPTS programs that you want to use, and set up each program as an individual input.
You also set up the POIS with information about the same set of inputs. In other words, the inputs must be set up in both Elemental Live and the POIS.
You start the event. As Elemental Live ingests the first input, it encounters SCTE-35 messages. It sends these messages to the POIS. It sends all SCTE-35 messages, not only switching-related messages. For example, it also sends ad avail messages.
For any switching-related message, the POIS might decide to send a request to Elemental Live to switch to another input at a specific time. The POIS can send this instruction at any time. There is no timeout between receiving the information and sending an instruction. The POIS might also decide not to send an instruction.
Types of requests
The following are the types of requests:
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Prepare input. This request makes Elemental Live start processing the input, even before the input is active. This preparation reduces the delay that always occurs between the switch request and the switch happening.
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Switch input. The POIS sends this request to instruct Elemental Live to switch, either immediately, or at a specific time.
The prepare input request should be sent at least 15 seconds before the switch request.
If the POIS sends a prepare input and a switch input, the switch will occur in less than 4 seconds.
If the POIS doesn't send a prepare input, the input switch can take as long as 12 seconds.
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SCTE-35 messages for ad avail handling. The POIS can request that Elemental Live insert an ad avail message, or delete or modify an ad avail message that is in the source stream (and that Elemental Live therefore sent to the POIS). For information about the handling of these types of SCTE-35 messages, see POIS conditioning.
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SCTE-35 messages that instruct Elemental Live whether to include the SCTE-35 in the output or not. The POIS can choose to instruct Elemental Live to include or to remove any of the three types of SCTE-35 messages.
Timing of input switching requests
The prepare input request should be sent at least 15 seconds before the switch request.
If the POIS sends a prepare input and a switch input, the switch will occur in less than 4 seconds. After the switch occurs, Elemental Live stops preparing the input.
If the POIS doesn't send a prepare input, the input switch might take as long as 12 seconds.
Result in outputs
If the POIS instructs Elemental Live to include an SCTE-35 message in the output, that message becomes part of the stream. This rule applies to all types of messages – prepare input, switch input, and messages relating to ad avails.
For a prepare input or switch input, Elemental Live still performs the action (prepare or switch), even if the POIS instructs Elemental Live not to include the message itself in the output.
Elemental Live includes these messages in output types that support SCTE-35 messages. For example, Elemental Live includes the messages in an HLS output.
For detailed information about how Elemental Live handles ad avail SCTE-35 messages, see POIS conditioning.
Example
Here's an example of an input switching scenario that illustrates the different input switching capabilities.
The time is 2:00:00. You start the event and Elemental Live starts ingesting the first input. At the same time, Elemental Live reads all the other inputs,
SCTE-35-triggered request
At 2:17:33, while ingesting input Y, Elemental Live encounters an SCTE-35 message. It sends the message to the POIS. Shortly after, the POIS sends a request to switch to input Z at 2:30:00.
At 2:30:00, Elemental Live switches to input Z (another live input).
SCTE-35 message that the POIS ignores
At 2:37:00, Elemental Live encounters an SCTE-35 message. It sends the message to the POIS, but the POIS doesn't send an input switch request. There is no rule that dictates that the POIS must switch on receiving a message.
Multiple SCTE-35-triggered requests
At 2:40:02, Elemental Live encounters another SCTE-35 message, and this time the POIS does respond by sending two requests. One request is to switch at 2:45:13 to input B (one of the ads that played previously). The second request is to switch at 2:45:43 back to input Z.
At 2:45:13, Elemental Live switches to input B.
At 2:45:43, Elemental Live switches back to input Z.
Canceled asynchronous request
At 2:51:44, the POIS sends a request to switch to input F at 2:52:00.
At 2:51:47, the POIS sends a request to cancel the switch to input F.
This example shows cancellation of an asynchronous request. The POIS can cancel either an asynchronous request of a SCTE-35-triggered request.
Multiple requests in an unexpected order
At 2:53:48, the POIS sends a request to switch to input D at 2:57:00.
At 2:54:00, the POIS sends a request to switch to input E at 2:55:30.
At 2:55:30, Elemental Live switches to input E. Then at 2:57:00, Elemental Live switches to input D.
Note that Elemental Live doesn't ignore the request to switch to input D, even though it received the request for input E in the meantime.
