# Latency Compensation

{% embed url="<https://youtu.be/_cS2Eb6S_60>" %}
This video explains how to compensate latency in Audacity
{% endembed %}

{% hint style="info" %}
**Note:** Latency Compensation is only important for the following recording scenarios:

* **Overdubbing**: recording a new audio track while listening to previously-recorded track(s).  You want what you play to be synchronized with the tracks you are listening to.
* **Punch and roll recording**
  {% endhint %}

## Measuring latency in your system

{% hint style="success" %}
There is an automated method available now, which is available at <https://forum.audacityteam.org/t/latency-test/65001>

It's currently in beta, so please leave your feedback in the forum thread
{% endhint %}

### Step 1: Adjust your Audacity preferences

#### 1. Set your Devices Preferences

* On Windows open the **Edit** menu and select **Preferences...** or press **`Ctrl + P`** in your keyboard. On macOS open the **Audacity** menu and select **Preferences...** or press **Cmd + P**
* Select **Devices** in the left pane of the **Preferences** window
* Select the preferred **Interface Host:** MME or Windows WASAPI should work
* Verify your preferred **Playback Device** is selected
* Verify your preferred **Recording Device** is selected
* Set the **Latency compensation** to 0 (zero) milliseconds
* Click **OK** to save your preferences

![Select Edit > Preferences... or press Ctrl + P to open Audacity Preferences and click on Devices](https://2387260374-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhmBVzGzh8SctWQ6jPR%2Fuploads%2FLywNweoOxNlxaIc68mlz%2FPreferences%20-%20Devices.png?alt=media\&token=901c3fbb-65c8-4126-9d9a-08b5250366ab)

#### 2. Set your Recording Preferences

* Select **Recording** in the left pane of the **Preferences** window
* Enable **Overdub**: Check **Play other tracks while recording (overdub)**
* Make sure **Software playthrough of input** is not checked
* Click **OK** to save your preferences

![Select Edit > Preferences... or press Ctrl + P to open Audacity Preferences and click on Recording](https://2387260374-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhmBVzGzh8SctWQ6jPR%2Fuploads%2FiqBbZAghcuZcHkwcCeGO%2FPreferences%20-%20Recording.png?alt=media\&token=a7c3323e-1616-450d-817b-895026b4a5be)

#### 3. Set your Selection preferences

At the bottom of the Audacity window you will find the **Selection** toolbar

* Disable snapping, if you have it enabled
* Select **Start and Length of Selection** as your selection format

![Audacity Selection Toolbar](https://2387260374-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhmBVzGzh8SctWQ6jPR%2Fuploads%2FRKtydnEhQL3Ig1H0LtoP%2FSelection%20toolbar.png?alt=media\&token=d9c2c160-347c-46f2-a435-79c515ce86e3)

### Step 2: Measuring the latency

#### Hardware Setup

To measure the latency you will need to record the audio from your playback device using your microphone.  To do this place your microphone next to your speakers/headphones

![Place your microphone next to your speakers or headphones](https://2387260374-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhmBVzGzh8SctWQ6jPR%2Fuploads%2F7UWmsHwsLKnZSuqaQyGW%2Fabcd.jpg?alt=media\&token=24373a9d-2250-4aea-b8e5-0e0ed7158f80)

#### Recording while playing a test track (Overdub)

* Open the **Generate** menu and select the **Rhythm Track...** option.  Set **Number of Measures (bars)** to 2 and set the **Beat Sound** to **Ping (short)**.  Click **OK** to generate the track.
* Press **Shift + R** to record a new track. The rhythm track will be played back and recorded on a new track.

![Recording a new track while playing the previously generated track (Overdub)](https://2387260374-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhmBVzGzh8SctWQ6jPR%2Fuploads%2Fil44B6jnpUpD2zZiOyJX%2FRhythym%20Overdub.png?alt=media\&token=b78b583a-1212-4978-ab55-d343a6c74d2d)

* Zoom in so you can see the clicks on the top track and its delayed version on the bottom track
* Create a selection that goes from the start of one click to the next

You should see something like this:

![Drag a selection to measure the latency](https://2387260374-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhmBVzGzh8SctWQ6jPR%2Fuploads%2FgXA6xRfjzF4mmMT4Geij%2FLatency%20estimation%20-%20Length%20of%20Selection.png?alt=media\&token=082601b7-ed64-4e27-9d33-2c1e34105775)

You can read the latency directly from the second panel of numbers. In this case it is 0.184 seconds or 184 milliseconds.

Click on **Edit > Preferences**, click on **Devices** tab and enter the negative of this number in the **Latency compensation** box. In this case it would be -184.  Press **OK** to save your preferences.

![Set Latency compensation value according to the measured latency](https://2387260374-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhmBVzGzh8SctWQ6jPR%2Fuploads%2FRq0aw8ogy2HYqOiaPKvD%2FLatency%20compensation%20-%20Set%20value.png?alt=media\&token=49106973-3514-4b85-9e2d-6609c9279aa2)

### Step 3: Checking the result

* Delete the second track by clicking the close box in its Track Control Panel
* Click in the Track Control Panel of the remaining track to select it
* Press **Shift + R** to record a new track

After the recording is finished Audacity will apply the Latency compensation by pushing the newly-recorded track back by the Latency compensation value.

![Recording with latency compensation applied to the second track](https://2387260374-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2F-MhmBVzGzh8SctWQ6jPR%2Fuploads%2FG0fwTU05Tlnb9PoHo4YV%2FOverdub%20Rhythym%20-%20Latency%20compensation.png?alt=media\&token=00f1e7bd-5b37-49b8-9cc4-43c28af42d4c)

{% hint style="info" %}
**Note:** If you change any of your recording or playback devices (for example, if you change from using the line input port on your computer to using a USB audio interface) or if you use the same device but change the [Audio Host](https://manual.audacityteam.org/man/device_toolbar.html#host) in [Device Toolbar](https://manual.audacityteam.org/man/device_toolbar.html), then you will need to do this test again. The test you just did only applies for the specific inputs and outputs and host used during the test.
{% endhint %}