# Planning the start type for an input prepare
<a name="input-prep-plan-start"></a>

Before you add an input prepare action to the schedule, decide on the start type for the action. 

**Topics**
+ [Types of starts for input prepares](plan-prep-start-types.md)
+ [Guidelines for choosing the start type](plan-prep-tips.md)

# Types of starts for input prepares
<a name="plan-prep-start-types"></a>

There are three start types for input prepare actions in MediaLive. These start types are the same as the start types for input switches.
+ Fixed – the input prepare starts at a specific time.
+ Immediate – the input prepare starts as soon as you add the action to the schedule.
+ Follow – the input prepare follows a specific input switch—the *reference input switch*. It can have a start or an end *follow point*—it can follow the start of the reference input or the end of the reference input. 

With the follow start type, the following rules apply:
+ You can't use the console to create a follow input prepare with a follow point set to *start*. The start option is not shown on the console. Only the end option is shown.
+ MediaLive starts preparing the input *after *the reference input is active. Therefore:
  + For a follow-start prepare (which you can create only using the CLI), you must add the prepare action before the reference input has started in the channel. 

    If the reference switch is an immediate switch, you must include the switch action and the prepare action in the same [batch update command](about-batch-update-schedule.md).

    If the reference switch is a fixed or follow switch, you can add the switch action in one batch update command, and the prepare action in a later batch update command.
  + For a follow-end prepare, you must add the prepare action before the reference input has ended (before ingest has ended).
+ You can't create two follow prepare actions that both follow the same reference switch and the same follow point. Therefore:
  + You *cannot* create action 2 and action 4 to both follow the start of action 1. 
  + But you can create action 2 to follow the *start* of action 1, and action 4 to follow the *end* of action 1.

# Guidelines for choosing the start type
<a name="plan-prep-tips"></a>

Following are some guidelines for deciding which start type to use with an input prepare in the MediaLive schedule. 

Keep in mind that you can only prepare one switch at a time. When a prepare action starts, MediaLive starts preparing the input, and automatically stops any other active prepare input action. 

Therefore, the guiding principle is to make sure that you don't start preparing input X and accidentally *stop *preparing input Y, if input Y needs to be prepared before input X. 

**Topics**
+ [Scenario A](#plan-prep-tips-scenario-A)
+ [Scenario B](#plan-prep-tips-scenario-B)
+ [Scenario C](#plan-prep-tips-scenario-C)
+ [Scenario D](#plan-prep-tips-scenario-D)

## Scenario A
<a name="plan-prep-tips-scenario-A"></a>

You are flipping between two inputs. The switch start is always undetermined, so that each switch is an immediate switch. There might be more switches interspersed among these switches, but they don't need preparing.

```
Switch to input A (immediate)
Switch to input B (immediate)
Switch to input A (immediate)
Switch to input B (immediate)
```

The easiest plan is to start preparing B after each switch to A, and to start preparing A after each switch to B. You could set up each prepare input action with any of these start types:
+ Fixed. The start time for prepare B is some time after the start time for switch A.
+ Immediate. Recommended. You could add the prepare B action at the same time as the immediate A switch, or shortly afterward.
+ Follow (start). You should add the prepare B action and the immediate A switch in the same [batch update command](about-batch-update-schedule.md). The reference action for the prepare B action is input A.
+ Follow (end). You can add the prepare B action at any time after switch A has been added to the schedule. The reference action for the prepare B action is input A.

For example:

```
Switch to input A (immediate)
Prepare input B (immediate)
Switch to input B (immediate)
Prepare input A (immediate)
Switch to input A (immediate)
Prepare input B (immediate)
Switch to input B (immediate)
```

## Scenario B
<a name="plan-prep-tips-scenario-B"></a>

There is an immediate switch to A, then there are several fixed or follow switches. You anticipate that the next immediate switch will be to A again. 

```
Switch to input A (immediate)
Switch to input C (fixed or follow)
Switch to input D (fixed or follow)
Switch to input A (immediate)
```

After the switch to A, MediaLive continues preparing A. Therefore, there is no need to prepare it again. Furthermore, if input A is the only input that ever has an immediate switch, you can prepare A once, before the first time that you switch to it. You don't need to prepare it again.

## Scenario C
<a name="plan-prep-tips-scenario-C"></a>

There is an immediate switch to A, then there are several fixed or follow switches. You anticipate that the next immediate switch will be to B. 

```
Switch to input A (immediate)
Switch to input C (fixed or follow)
Switch to input D (fixed or follow)
Switch to input B (immediate)
```

You know that the next immediate switch will be to input B, so you can start preparing it anytime after the switch to input A. You could set up each prepare input action with any of these start types:
+ Fixed. The start time for prepare B is at least 10 seconds before the start of switch B.
+ Immediate. Recommended. You could add the prepare B action at the same time as the immediate A switch, or shortly afterward.
+ Follow (start). Not recommended. You could, for example, set up the prepare B action to follow the start of switch C or the start of switch D.
+ Follow (end). Not recommended. You could, for example, set up the prepare B action to follow the end of switch A or the end of switch C. Don't set it up to follow the end of switch D.

For example:

```
Switch to input A (immediate)
Prepare input B (immediate)
Switch to input C (fixed or follow)
Switch to input D (fixed or follow)
Switch to input B (immediate)
```

## Scenario D
<a name="plan-prep-tips-scenario-D"></a>

There is an immediate switch to input B, then there are several fixed or follow switches. You anticipate that there will be another immediate switch but initially you don't know if it will be to input B or input E. 

```
Switch to input A (immediate)
Switch to input C (fixed or follow)
Switch to input D (fixed or follow)
Switch to input B or E (immediate)
```

When you know which input you will switch to, you can start preparing it. When you want to prepare it, the current input could be A, C, or D. You could set up each prepare input action with any of these start types:
+ Fixed. The start time for prepare B (or E) is at least 10 seconds before the start of switch B (or E).
+ Immediate. Recommended. Add the prepare input action as soon as you know whether the switch will be to B or E.
+ Follow (start). Not recommended. You could, for example, set up the prepare B (or E) action to follow the start of switch C or the start of switch D.
+ Follow (end). Not recommended. You could, for example, set up the prepare B (or E) action to follow the end of switch A or the end of switch C. Don't set it up to follow the end of switch D.

For example:

```
Switch to input A (immediate)
Switch to input C (fixed or follow)
Switch to input D (fixed or follow)
Prepare input E (immediate)
Switch to input E (immediate)
```