# Setting the fragment length for streaming outputs
<a name="setting-the-fragment-length"></a>

For all ABR streaming output groups other than HLS (CMAF, DASH, and Microsoft Smooth Streaming), the value that you specify for **Fragment length** (`FragmentLength`) must work with the other output settings that you specify. If you set **Fragment length** incorrectly, when viewers watch the output video, their player might crash. This can happen because the player expects additional segments at the end of the video and requests segments that don't exist. 

**Fragment length** is constrained by your values for **Closed GOP cadence** (`GopClosedCadence`), **GOP size** (`GopSize`), and **Frame rate** (`FramerateNumerator`, `FramerateDenominator`). For information about finding these settings on the console and in your JSON job specification, see [Finding the settings related to fragment length](#finding-the-settings-related-to-fragment-length).

**Note**  
When you set your output **Frame rate** to **Follow source**, make sure that the frame rate of your input video file works with the value that you specify for the output **Fragment length**. The frame rate of your input video file functions as your output frame rate. 

**Topics**
+ [Rule for fragment length](#rule-for-fragment-length)
+ [Fragment length examples](#fragment-length-examples)
+ [Finding the settings related to fragment length](#finding-the-settings-related-to-fragment-length)

## Rule for fragment length
<a name="rule-for-fragment-length"></a>

Fragment length must be a whole number and must be a multiple of this value: **GOP size** x **Closed GOP cadence** ÷ **Frame rate**

## Fragment length examples
<a name="fragment-length-examples"></a>

**Example: Correct settings**  
Closed GOP cadence = 1

Frame rate = 30

GOP size = 60 frames

Fragment length = 2

**Example: Incorrect settings**  
Closed GOP Cadence = 1

Frame rate = 50

GOP size = 90 frames

Fragment length = 2

## Finding the settings related to fragment length
<a name="finding-the-settings-related-to-fragment-length"></a>

When you set **Fragment length**, check your values for **Closed GOP cadence**, **GOP size**, and **Frame rate**.

### Fragment length
<a name="fragment-length"></a>

You can set the fragment length using either the console or the JSON job specification. The **Fragment length** setting applies to an output group and affects every output in the group.

**To find the **Fragment length** setting (console)**

1. On the **Create job** page, in the **Job** pane on the left, under **Output groups**, choose the name of your CMAF, DASH ISO, or Microsoft Smooth Streaming output group.

1. In the group settings section on the right, find **Fragment length**. 

   The group settings section is titled **CMAF group settings**, **DASH ISO group settings**, or **MS Smooth group settings**.

**To find the **Fragment length** setting (JSON job specification)**
+ Find `FragmentLength` as a child of `OutputGroupSettings`, as in the following example.

  ```
  {
    "Settings": {
      ...
      "Inputs": [
        ...
      ],
      "OutputGroups": [
        {
          "Name": "DASH ISO",
          "OutputGroupSettings": {
            "Type": "DASH_ISO_GROUP_SETTINGS",
            "DashIsoGroupSettings": {
              "SegmentLength": 30,
              "FragmentLength": 2,
              "SegmentControl": "SINGLE_FILE",
              "HbbtvCompliance": "NONE"
            }
          },
  		...
  ```

### Closed GOP cadence, GOP size, and frame rate
<a name="closed-gop-cadence-gop-size-and-framerate"></a>

You can set **Closed GOP cadence**, **GOP size**, and **Frame rate** using either the console or the JSON job specification. These settings apply to each output individually. Make sure that the values that you set for each output in the output group work with the value that you specify for the output group's **Fragment length**.

**Note**  
Your ABR stack has multiple outputs. Make sure to set these values in each output.

**To find the encoding settings for an output (console)**

1. On the **Create job** page, in the **Job** pane on the left, under **Output groups**, choose the name of your output, such as **Output 1**, **Output 2**, and so on.

1. In the **Encoding settings** section, the **Video** tab is selected automatically. Find **Closed GOP cadence**, **GOP size**, and **Frame rate** on this tab.

**To find the encoding settings for an output (JSON job specification)**
+ 

Find `GopClosedCadence`, `GopSize`, `FramerateNumerator`, and `FramerateDenominator` as children of the codec settings, as in the following example. In this example, the codec is `H_264`, so the parent of the codec settings is `H264Settings`.

  ```
  {
    "Settings": {
      ...
      "Inputs": [
        ...
      ],
      "OutputGroups": [
        {
          "Name": "DASH ISO",
          ...
          },
          "Outputs": [
            {
              "VideoDescription": {
                ...
                "CodecSettings": {
                  "Codec": "H_264",
                  "H264Settings": {
                    "InterlaceMode": "PROGRESSIVE",
                    "NumberReferenceFrames": 3,
                    "Syntax": "DEFAULT",
                    "Softness": 0,
                    "GopClosedCadence": 1,
                    "GopSize": 60,
  				  ...
                    "FramerateNumerator": 60,
                    "FramerateDenominator": 1
                  }
                },
                ...
              },
  ```