# Syncing to a timecode

To sync LightAct to an external timecode the process is as follows:

1. **Receive external TC**: LightAct can receive LTC through Audio input nodes, MTC through MIDI Receiver nodes (both in the Devices window) and Art-Net timecode through DMX In window. This is described in the relevant chapters.
2. **Sync Timeline group to incoming TC.**
3. **Sync a Timeline to its Timeline group.**

## Receive external timecode

Refer to [**Audio Input**](https://docs.lightact.com/integrations/audio), [**MIDI Receiver**](https://docs.lightact.com/osc-and-midi/midi) or [**Receiving DMX** ](https://docs.lightact.com/dmx/dmx-in)user docs to learn how to do that.

## Sync Timeline group to incoming timecode

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Once you are receiving your MTC, LTC or Art-Net timecode, the next step is to select the **Timeline group** you'd like to sync to it.

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In the **Source** dropdown select the TC Source you'd like to sync to.

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In the Timelines window, you'll be able to see the incoming TC + *Timecode offset*.

### Engaged/Disengaged mode and sync status

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If a Timeline group is **Engaged**, it means it will be locked to the incoming TC if a valid one is arriving. In this case, to the right of the Engaged/Disengaged button, you'll be able to see 3 statuses:

1. **No TC source**: this means you haven't selected a Sync source in the Properties of the Timeline group.
2. **No TC**: this means you have selected a TC source, but that TC source is not receiving and TC
3. **Chasing TC**: this means the selected TC source is receiving a valid TC

### Grace period

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If TC stops and you enable **Grace period** in the Properties of Timeline group, LightAct will for the set duration of time assume that TC will resume.

{% hint style="info" %}
**Good to know**: A grace period could be useful to cover intermittent, unintentional breaks in incoming TC.
{% endhint %}

{% hint style="info" %}
**Good to know**: if your TC source is LTC, LightAct includes a bit-flip prevention feature. This means that if, due to audio noise, the incoming LTC suddenly jumps, LightAct will ignore it unless subsequent LTC frames confirm that the jump is intentional.
{% endhint %}

## Sync Timeline to its Timeline group

The steps you will want to follow is to:

1. Determine in which **Sections** you want the Timeline to be synced to incoming TC.
2. Determine their **Start TC** marks
3. Enable **Engaged** status

### Sync sections

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In the Sync sections part of the Properties of a Timeline, you determine in which Sections you'd like this Timeline to be synced to the incoming TC. You can choose:

1. **Sync in all sections**: all sections will be chasing TC if it falls within them
2. **Sync in selected sections**: only the selected sections will be chasing TC if it falls within them.
3. **Sync in unselected sections**: only the unselected sections will be chasing TC if it falls within them.

#### Section TC marks

Every synced section has a property called **Start TC**. This property determines at what TC will this section start chasing TC.

{% hint style="info" %}
**Good to know**: enable **Show start TC labels** checkbox to see how Start TC times are set up.
{% endhint %}

There are 2 types of determining the **Start TC** of every section:

1. **Automatic**: Start TC is the same as that section's position in the timeline. For example, if section starts at 00:01:50:23 of the timeline, its Start TC is also going to be 00:01:50:23
2. **Custom**: if you choose this type, then you can set up a custom Start TC time.

{% hint style="info" %}
**Good to know**: if a section with an Automatic type is positioned AFTER a section with Custom type, its Start TC time will be calculated based on the time difference between the start of the section with the Custom type and its own.
{% endhint %}

{% hint style="info" %}
**Good to know**: if a section has a Custom **Start TC** time and it's selected you can nudge the Start TC time by one frame with Ctrl & + and Ctrl & - shortcuts.
{% endhint %}

### Engaged/Disengaged mode and sync status

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To sync a Timeline to its Timeline group, simply switch its sync mode to Engaged. In this case, there are several different statuses that a Timeline can be in:

1. **Group not chasing TC**: this status means that the parent Timeline group is not chasing any TC, so the Timeline also isn't.
2. **Chasing TC**: this means that the Timeline is chasing incoming TC.
3. **Outside synced sections**: this means that the incoming TC does not fall within any synced section.
4. **Ignoring TC**: this means that the incoming TC falls within a synced section, but there was a manual trigger that caused the timeline to temporarily ignore the TC. Manual trigger means manual pressing of one of the play state buttons (play, pause etc.) a cue trigger or something else. If the incoming TC jumps and is still within a synced section the Timeline will start chasing the TC again.&#x20;