# AMCP Commands Review

From the [CasparCG AMCP command page](https://github.com/CasparCG/help/wiki/AMCP-Protocol), "The Advanced Media Control Protocol (AMCP) is the main communication protocol used to control and query CasparCG Server." I would recommend saving that link, it will make getting back to the AMCP commands much easier in the future. 

We are primarily interested in the [Template Commands](https://github.com/CasparCG/help/wiki/AMCP-Protocol#template-commands). Let's break each of them down and explain how each of them can be used with our JavaScript file. If you are already familiar with the AMCP commands, you can skip to the [next section](https://chrisryanouellette.gitbook.io/casparcg-html-template-guide/html-templates/the-basics).

### CG ADD

CG ADD will load the HTML file from an URL or a file in the templates folder defined in your `casparcg.config` file. Each HTML file loaded will be displayed on a device and occupy one layer. The channel and layer are defined as the first two properties in the CG ADD command.

```javascript
CG [channel: int]-[layer: int] ADD
CG 1-1 ADD
CG 1-999 ADD // 999 is the max layer
```

The next parameter is the flash layer. This has no effect on our HTML template so we will always set it to `0`.

```javascript
CG [channel: int]-[layer: int] ADD [Flash Layer: int]
CG 1-1 ADD 0
```

The next parameter is an URL or name of a HTML file in the templates folder. If you are using the HTTP-Server package setup in the [Development Setup](https://chrisryanouellette.gitbook.io/casparcg-html-template-guide/development-setup#web-server) section of this guide, then your command will look like the following.

```javascript
CG [channel: int]-[layer: int] ADD [Flash Layer: int] [URL: string]
CG 1-1 ADD 0 http://localhost:8080/lower-third.1.html
```

To load a file from the CasparCG templates folder, remove the extension from the filename like so.

```javascript
CG 1-1 ADD 0 lower-third.1
CG 1-1 ADD 0 folder/lower-third.1 // If you nested the file in a folder
```

{% hint style="warning" %}
CasparCG version 2.1.1 NRK Build will only load files from the templates folder.
{% endhint %}

Next, we can add a Play On Load parameter that is either `0` or `1`. For now, we will set it to `0`.

```javascript
CG [channel: int]-[layer: int] ADD [Flash Layer: int] [URL: string] [Play On Load: bool] [Data: string]
CG 1-1 ADD 0 http://localhost:8080/lower-third.1.html 0
```

Finally, we can add some optional data. We will define that in the [Handling AMCP Commands](https://chrisryanouellette.gitbook.io/casparcg-html-template-guide/javascript/handling-updates#template-data-setup) within the JavaScript section of this guide.

### CG UPDATE

CG UPDATE calls the JavaScript file's `update` global function. It is also the only function that is passed a string of data. The CasparCG Server website says it is either string of JSON or XML data but, it can be any string. We will primarily be using JSON. We do need to escape the double quotes because CasparCG Server will not recognize single quotes as a string.

```javascript
CG [channel: int]-[layer: int] UPDATE "{}"
CG 1-1 UPDATE "{\"some\":\"data\"}"
```

### CG PLAY

CG PLAY will call the JavaScript file's `play` global function. It is designed to animate in the graphic.

```javascript
CG [channel: int]-[layer: int] PLAY
CG 1-1 PLAY
```

### CG NEXT

CG NEXT will call the JavaScript file's `next` global function. It is designed to advance the template to the next step. We will also be defining a non-standard function called `previous`. 

```javascript
CG [channel: int]-[layer: int] NEXT
CG 1-1 NEXT
```

### CG STOP

CG STOP will call the JavaScript file's `stop` global function. It is designed to animate out the graphic.

```javascript
CG [channel: int]-[layer: int] STOP
CG 1-1 STOP
```

### CG REMOVE

CG REMOVE will call the JavaScript file's `remove` global function. It is designed to prepare a graphic to be cleared. This can include things like saving local data, or making API calls.

```javascript
CG [channel: int]-[layer: int] REMOVE
CG 1-1 REMOVE
```

### CG INVOKE

CG INVOKE calls a custom function defined on the JavaScript file's global scope. In this guide, we will define the `reset` and `previous` functions to be invoked by the CasparCG server.

```javascript
CG [channel: int]-[layer: int] INVOKE [Flash Layer: int] [Function Name: string]
CG 1-1 INVOKE 0 reset
CG 1-1 INVOKE 0 previous
```

### CG CLEAR

CG CLEAR will not interact with our JavaScript file at all. It will immediately clear the layer or channel provided. This will also remove our template if it is on that channel or layer. 

```javascript
CG [channel: int] CLEAR // Clears an entire channel
CG [channel: int]-[layer: int] CLEAR // Clears a specific channel and layer
```

#### Resources

* [AMCP Commands](https://github.com/CasparCG/help/wiki/AMCP-Protocol) on the CasparCG Wiki