# Configure Audio Codec for the Cloud Voice App Mobile Client

A codec (short for coder/decoder) is the method the app uses to compress and decompress call audio. Cloud Voice supports several codecs so you can balance call quality against how much bandwidth each call uses on the Cloud Voice App mobile client. From the PBX (Private Branch Exchange, the phone system) web portal you can apply one codec to every user as a default, or assign a specific codec to an individual extension when their needs differ.

:::note
The steps below cover configuration from the PBX web portal. Extension users can also pick their own codec directly in the app under **Account > Settings > Audio Options > Codec**, and any change they make is synced back to the PBX automatically.
:::

## Requirements

Before you begin, confirm these minimum versions:

- **PBX server**: `84.15.0.22` or later.
- **Cloud Voice App mobile client**:
  - iOS: version 5.5.9 or later.
  - Android: version 5.5.8 or later.

:::caution
If either the PBX server or the app is older than the versions above, the codec setting may not appear or may not sync. Update first, then configure.
:::

## Set a default codec for all mobile clients

Use this procedure to define the codec that applies across every user's Cloud Voice App mobile client.

1. Sign in to the PBX web portal and go to **Extension and Trunk > Extension**.
2. Above the extension list, click **Cloud Voice App Server**.
3. Scroll to the **Cloud Voice App Mobile Default Settings** section and do the following:
   1. From the **Cloud Voice App Mobile Client Codec** drop-down list, choose an audio codec.

      :::tip
      A codec that uses less bandwidth helps on weak or metered mobile-data connections, while a higher-bandwidth codec can give better audio when the network is strong. Match the choice to how your users usually connect.
      :::

      
      ![Cloud Voice, the mobile default settings section with the codec drop-down selected](/images/pbx/linkus-server-mobile-codec.png)
   2. Click **Save**.
   3. In the window that appears, decide whether the codec should apply only to new extensions or to all extensions (both new and existing), then click **Confirm**.

      :::caution
      Choosing **all extensions** overwrites any codec you previously set for individual users. Pick **new extensions only** if you want to keep existing per-user choices intact.
      :::

      ![Prompt asking whether to apply the codec to new extensions only or to all extensions](/images/pbx/global-codec-application-range.png)

The codec is pushed to users' Cloud Voice App mobile clients and takes effect right away.

## Set a codec for a single user

Use this procedure when one extension needs a different codec than the default.

:::note
A codec set here applies to this extension only. It stays in place even if you later change the global default, unless you apply that default to all extensions.
:::

1. Sign in to the PBX web portal and go to **Extension and Trunk > Extension**.
2. Click the edit icon ![Edit](/images/pbx/edit-1.png) next to the extension you want to change, then open the **Cloud Voice App Clients** tab.
3. From the **Cloud Voice App Mobile Client Codec** drop-down list, choose an audio codec.

   
   ![Cloud Voice, selecting a codec for one extension on the clients tab](/images/pbx/select-codec-for-single-client.png)
4. Click **Save**.

The codec is pushed to that user's Cloud Voice App mobile client and takes effect right away.