# Manage stream state (/en/realtime-media/iot/build/manage-connections-and-quality/stream-state)

> For AI agents: see the complete documentation index at [llms.txt](/llms.txt).

After you join a channel on a connection and start streaming, you can pause and resume sending local audio or video to a specific connection or to all connections. You can also pause and resume receiving audio or video from a specific remote user or all remote users.

This page shows you how to mute and unmute local and remote audio and video streams in your IoT SDK app.

## Prerequisites

In order to follow this procedure you must have:

* Implemented the basic IoT SDK functionality. See [Build from scratch](../../build-from-scratch.mdx).

## Send stream state

To pause or resume sending local audio or video, call `agora_rtc_mute_local_audio` or `agora_rtc_mute_local_video` with the connection ID and a mute flag (`1` to mute, `0` to unmute):

```cpp
// Pause sending audio to a specific connection
agora_rtc_mute_local_audio(conn_id, 1);
// Resume sending audio to a specific connection
agora_rtc_mute_local_audio(conn_id, 0);
// Pause sending video to a specific connection
agora_rtc_mute_local_video(conn_id, 1);
// Resume sending video to a specific connection
agora_rtc_mute_local_video(conn_id, 0);
```

<CalloutContainer type="info">
  <CalloutDescription>
    Pass `0` as the connection ID to mute or unmute all of your connections at once, instead of a single connection.
  </CalloutDescription>
</CalloutContainer>

## Receive stream state

### Handle mute notifications from remote users

When a remote user mutes or unmutes their audio or video stream, IoT SDK notifies you through the `on_user_mute_audio` and `on_user_mute_video` callbacks:

```c
static void __on_user_mute_audio(connection_id_t conn_id, uint32_t uid, bool muted) {
    printf("[conn-%u] audio: uid=%u muted=%d\n", conn_id, uid, muted);
}

static void __on_user_mute_video(connection_id_t conn_id, uint32_t uid, bool muted) {
    printf("[conn-%u] video: uid=%u muted=%d\n", conn_id, uid, muted);
}
```

### Pause and resume receiving remote streams

To pause or resume receiving a remote user's audio or video, call `agora_rtc_mute_remote_audio` or `agora_rtc_mute_remote_video` with the connection ID, the remote user's ID, and a mute flag:

```cpp
const uint32_t remote_uid = 789;
// Pause receiving audio from a remote user on a specific connection
agora_rtc_mute_remote_audio(conn_id, remote_uid, 1);
// Resume receiving audio from a remote user on a specific connection
agora_rtc_mute_remote_audio(conn_id, remote_uid, 0);
// Pause receiving video from a remote user on a specific connection
agora_rtc_mute_remote_video(conn_id, remote_uid, 1);
// Resume receiving video from a remote user on a specific connection
agora_rtc_mute_remote_video(conn_id, remote_uid, 0);
```

## Reference

* [on\_user\_mute\_audio](https://api-ref.agora.io/en/iot-sdk/linux/1.x/structagora__rtc__event__handler__t.html#a5c823e048831fcefa7fca0a2c01ad864)
* [on\_user\_mute\_video](https://api-ref.agora.io/en/iot-sdk/linux/1.x/structagora__rtc__event__handler__t.html#ae07cf9b3a19154ad8d889a4bd3f51b59)
* [agora\_rtc\_mute\_local\_audio](https://api-ref.agora.io/en/iot-sdk/linux/1.x/agora__rtc__api_8h.html#a28c1dae086be4014ad732a07db248b16)
* [agora\_rtc\_mute\_local\_video](https://api-ref.agora.io/en/iot-sdk/linux/1.x/agora__rtc__api_8h.html#a47f116e271b78c0659fcd68a96d34224)
* [agora\_rtc\_mute\_remote\_audio](https://api-ref.agora.io/en/iot-sdk/linux/1.x/agora__rtc__api_8h.html#a8ad8bfa0e0a46a0c5e7fae11449ab575)
* [agora\_rtc\_mute\_remote\_video](https://api-ref.agora.io/en/iot-sdk/linux/1.x/agora__rtc__api_8h.html#a894f5a102c66b20c408bb495ac424efa)