How to Fit Music to a Set Length in AudioDirector
Shorten or lengthen background music so it ends right when your video does.
Updated Nov. 4, 2026 · 3 min read
In a hurry? Use the music length quick guide instead.
AudioDirector's Adjust Duration (Smart Fit) tool, the Auto Adjust Length feature, remixes a song to the length you type. It loops or cuts sections of the music instead of changing its speed. Use it when background music has to match your video, such as a 2:19 song that needs to last exactly 1 minute.
- In the Mix room, select the song on a track.
- In Editing Tools, click Adjust Duration (Smart Fit).
- Type the New audio duration and press Enter.
- Preview the remix, click Apply, then click OK.
- Click Export, choose a format, and click Export again.
Steps to Fit Music to a Set Length
Step 1: Open Adjust Duration (Smart Fit)
Click Mix at the top of the window. Drag your song from the library onto a track, then click the clip on the track to select it. This example uses Mahoroba.mp3, a 2:19 sample clip from CyberLink.
In the Editing Tools panel at the bottom left, click Adjust Duration (Smart Fit). AudioDirector analyzes the clip first, and the panel is ready when the progress bar finishes.
Smart Fit works only in the Mix room, on one clip at a time. It stays gray until you select a clip on a track.
Step 2: Type the New Audio Duration
New audio duration starts at the clip's current length, here 0:02:19.351. Click the hours, minutes, seconds, or milliseconds, type the new number, and press Enter. The new length can't be shorter than 10 seconds.
The clip on the track changes to the new length right away. Curvy lines on the waveform mark where AudioDirector remixed the music.
To fine-tune the remix, click the gear icon (Advanced) at the right of the field. You can keep the defaults for a first try:
| Setting | What it does |
|---|---|
| Stretch to exact duration | Makes the clip exactly the length you typed, for example when you make a song longer. It's checked by default. Clear it, and the clip can end a little off that length, within the Max slack. |
| Segments | Changes the content and sound of the remix, from Short to Long (0 to 100, default 100). Shorter segments loop more of the audio and add more remix points. |
| Max slack (seconds) | Sets how far the new length may drift, from 1 to 30 seconds (default 5). Drag left for a length closer to the one you typed. Drag right when the length can be approximate, for a remix that sounds closer to the original. |
This example types 0:01:00.000 and keeps the defaults.
Step 3: Preview and Click Apply
Hover over a curvy line on the clip to see its remix details, such as "Remixed from 0:00:51.200 to 0:01:04.319."
Under Preview, keep Adjusted result selected and click the play button on the playback controls below the timeline. Listen across the curvy lines to check that each section flows into the next. Select Original audio to compare it with the full song. To start over, click Back to default, the last icon at the top right of the panel.
When it sounds right, click Apply.
Step 4: Click OK
A message tells you the adjustment is complete. Click OK.
The clip on the track is now 1 minute long and named *Mahoroba.mp3. The asterisk marks an edited version that isn't exported yet, and the icon at the clip's bottom left shows it has been edited. Your original file on disk doesn't change.
Step 5: Export the Clip
Click Export at the top of the window. In Export Audio, type a File name, then click the ... button next to Location to choose a folder.
Click the Format list and choose WAV, WMA, MP3, M4A, FLAC, or APE. WAV, FLAC, and APE are lossless formats, so they keep all the audio data in the clip. With MP3, you can also edit the file's metadata. Then click Export.
In the Mix room, Export mixes all the tracks into one file. If the mix includes a video, choose Export Audio after you click Export. This example exports a WAV file at 48000 Hz, 16 bits, in stereo. The file is exactly 1:00.000 long, and AudioDirector also adds it to the library, so you can use it in other projects.
The other settings in Export Audio are optional:
| Setting | What it does |
|---|---|
| Upload a copy to CyberLink Cloud | Also saves the file to your CyberLink Cloud storage, if you have a CyberLink Cloud subscription. |
| Bitrate or Compression level | Sets the bitrate of the file. For FLAC and APE, a higher compression level makes a smaller file but takes longer to export. |
| Sample rate and Bit depth | Set the audio quality of the file. |
| Channels | Sets the number of channels. WAV and FLAC can also export 5.1 or 7.1. |
| CyberLink TrueTheater Surround | Improves the sound when you add channels. Choose Living Room, Theater, or Stadium. |
We tested these steps in AudioDirector 365 version 17.0.6908 on Windows.
Don't have AudioDirector yet? Remix a song to the length of your video and export it as a new file.
Download AudioDirector Free →FAQ About Fitting Music to a Set Length in AudioDirector
No. Adjust Duration (Smart Fit) changes the length by remixing sections of the song, so the tempo stays the same. To speed a clip up or slow it down instead, use Adjust Duration (Change Speed).
Smart Fit works only in the Mix room, on one clip on a track. Drag the song from the library onto a track and click the clip to select it. If you select more than one clip, the editing tools aren't available.
Yes. Type a length longer than the clip, and AudioDirector remixes it to fill the time. Keep Stretch to exact duration checked to make it exactly that length. The new length can't be shorter than 10 seconds.
