> For the complete documentation index, see [llms.txt](https://docs.convai.com/api-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.convai.com/api-docs/plugins-and-integrations/convai-unreal-engine-plugin/features/lip-sync/record-and-replay-lip-sync.md).

# Record and replay lip sync

The `UConvaiFaceSyncComponent` recording API lets you capture the blendshape frames that arrive during a live conversation and replay them on demand without re-streaming from Convai. Use it for cutscenes where the same lip-sync sequence plays back repeatedly, for pre-warming a response before it is triggered, or for debugging and offline preview of facial animation.

{% hint style="warning" %}
The recording API — `StartRecordingLipSync`, `FinishRecordingLipSync`, `PlayRecordedLipSync`, `IsPlaying`, and `GetCurrentFrame` — is C++ only. These methods have no `UFUNCTION` decoration and are not accessible from Blueprints.
{% endhint %}

### When to use the recording API

| Use case                                | Approach                                                                            |
| --------------------------------------- | ----------------------------------------------------------------------------------- |
| Cutscene with a fixed character speech  | Record once during development, store the sequence, replay in the cutscene          |
| Pre-warmed response cache               | Record the response on first play, replay for subsequent identical responses        |
| Offline facial animation preview        | Record during a PIE session, inspect frame data with `GetCurrentFrame()`            |
| Live streaming (real-time conversation) | Do not use the recording API — the AnimGraph node handles live frames automatically |

### Prerequisites

* The Actor has a `Convai Face Sync` component and a working `Convai Chatbot` component.
* The character already produces lip sync during conversation (see [Lip sync quick start](/api-docs/plugins-and-integrations/convai-unreal-engine-plugin/features/lip-sync/lip-sync-quick-start.md) if not).

### Record a sequence

{% stepper %}
{% step %}

#### Start recording before the speech turn

Call `StartRecordingLipSync()` on the `UConvaiFaceSyncComponent` instance. From this point, every blendshape frame delivered by Convai is buffered internally in addition to being applied to the face.

```cpp
// pseudocode
UConvaiFaceSyncComponent* FaceSync = MyCharacter->FindComponentByClass<UConvaiFaceSyncComponent>();
if (FaceSync)
{
    FaceSync->StartRecordingLipSync();
}
```

{% endstep %}

{% step %}

#### Let the character speak

Trigger a conversation as normal. The character speaks and its face animates. The component captures the incoming frames in the background — no additional calls are required while recording.
{% endstep %}

{% step %}

#### Stop recording and store the result

When the speech turn ends, call `FinishRecordingLipSync()`. The method stops capturing and returns an `FAnimationSequenceBP` containing the full list of frame-indexed blendshape frames, the total duration, and the frame rate.

```cpp
// pseudocode
FAnimationSequenceBP CachedSequence = FaceSync->FinishRecordingLipSync();
```

Store this value as a member variable on your Actor or component so you can replay it later. At this point you have the complete facial animation that played during the conversation turn.
{% endstep %}
{% endstepper %}

### Replay a recorded sequence

Call `PlayRecordedLipSync` on the `UConvaiFaceSyncComponent` instance to replay the stored sequence. The component feeds the recorded frames to the AnimGraph node exactly as it would during a live stream, with no active Convai conversation stream required.

#### PlayRecordedLipSync parameters

| Parameter           | Type                   | Description                                                                                           |
| ------------------- | ---------------------- | ----------------------------------------------------------------------------------------------------- |
| `RecordedLipSync`   | `FAnimationSequenceBP` | The sequence returned by `FinishRecordingLipSync`.                                                    |
| `StartFrame`        | `int32`                | Index of the first frame to replay. Pass `0` to start from the beginning.                             |
| `EndFrame`          | `int32`                | Index of the last frame to replay. Pass `-1` to play to the end of the sequence.                      |
| `OverwriteDuration` | `float`                | Override the sequence's stored playback duration in seconds. Pass `0.0` to use the original duration. |

`PlayRecordedLipSync` returns `bool` — `true` if the sequence started successfully. It returns `false` if the sequence is empty or invalid, recording is still active, `StartFrame` is greater than the last frame index, or `EndFrame` is greater than `0` and less than `StartFrame`.

```cpp
// pseudocode
bool bStarted = FaceSync->PlayRecordedLipSync(CachedSequence, 0, -1, 0.0f);
```

### Monitor playback state

Use these C++ methods to observe the component while a recorded sequence is playing:

| Method              | Returns              | Description                                                                                                                       |
| ------------------- | -------------------- | --------------------------------------------------------------------------------------------------------------------------------- |
| `IsPlaying() const` | `bool`               | `true` when the component is actively replaying frames from a recorded or live sequence.                                          |
| `GetCurrentFrame()` | `TMap<FName, float>` | The blendshape name-to-weight map for the frame currently being applied. Useful for driving secondary systems from the same data. |

### Example C++ flow

A typical cutscene usage looks like this:

```cpp
// pseudocode
// 1. Before or at the start of the speech turn:
FaceSync->StartRecordingLipSync();

// 2. The character speaks — recording happens automatically in the background.

// 3. When the speech turn ends:
FAnimationSequenceBP CachedSequence = FaceSync->FinishRecordingLipSync();

// 4. When you want to replay the sequence (e.g. on cutscene trigger):
FaceSync->PlayRecordedLipSync(CachedSequence, 0, -1, 0.0f);
```

{% hint style="info" %}
Replaying a sequence does not re-trigger audio. Play the matching audio clip separately and align playback start times to keep the face and voice in sync.
{% endhint %}

### Next steps

{% content-ref url="/pages/lsZCsc7Ypsg79ozXB0fr" %}
[Face Sync component reference](/api-docs/plugins-and-integrations/convai-unreal-engine-plugin/features/lip-sync/face-sync-component-reference.md)
{% endcontent-ref %}

{% content-ref url="/pages/n5M1eapXfiR0tOlawpbm" %}
[Lip sync usage examples](/api-docs/plugins-and-integrations/convai-unreal-engine-plugin/features/lip-sync/lip-sync-usage-examples.md)
{% endcontent-ref %}


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