Premiere Pro 2025 Version 25.0.0 doesn't accept .mts files with sound?

[TomWho]

We just got a new PC with Premiere Pro 2025 Version 25.0.0 (Build 61).  When I import .mts files and drag them onto the timeline there is no audio track (on a known good file - checked in VLC).  We've got an older system with Version 24.6.1 (Build 2) that doesn't have any trouble with the same .mts file.   I was able to convert the file to .mp4 using VLC and edit the program successfully in 25.5.0, but that's time consuming.  Is there a way to get 25.0.0 to accept .mts files?

PC - Dell Precision 5860 Tower

OS - Windows 11 Pro for Workstations, Version 24H2

Basic steps - Import known good .mts file, drag from bin to timeline

Expected results - A video track AND an audio track

[Ann Bens · Accepted solution]

Its not a bug.

If you have a brand new W 11 installed, than that is correct: no sound.

W11 24H2 does not support ac3 anymore.

You will have to download or buy the ac3 codec and install it into Windows 11.

[TomWho]

Thank-you!

[Averdahl]

@TomWho This one will solve the issue: Download Dolby AC-3/AC-4 Installer - MajorGeeks

More info here: https://community.adobe.com/t5/premiere-pro-discussions/no-ac3-codec-in-windows-11-24h2-solution-is-...

[wxthings]

Did installing the Dolby decoder completely fix the problem? I have the same issue on two different Win 11 computers. After installing the decoder, I do get audio on MTS clips, but the audio leads the video by about 20 frames. It may not be noticeable on nat sound clips, but it is painfully noticeable on spoken audio being out of synch. The visual clue to this in a sequence is no waveform appearing at the original end of each clip. 

[TomWho]

The sound was out of sync for me, but I unlinked the video from the audio and shifted 20 frames.

[Averdahl]

Unfortunately there are two issues at the same time here...

The first is that the audio is gone that could be solved by installing the Dolby decoder. The second issue is that Premiere Pro 25 do play back the Dolby audio out of sync, and that´s a bug in Premiere Pro. 

I updated to 25.1.0 (Build 73) two days ago and the small testing i did then was positive. The clips i imported did playback in sync. I am not sure yet that it is fixed since Pr 24 behaved the same. In Pr 24 some imported clips played back in sync only to playback out of sync the day after.

If you have Premiere Pro 25.1.0 you can try to launch it while holding down the Shift key and in the Reset options dialog that pops up check Clear media cahce files and then click on Continue. Open the project when done and let the files conform fully until you start to edit the project. And if you have 25.0, update to 25.1.

The 100%-working solution is to download Premiere Pro 23.6.8 from the Creative Cloud app. But then projects made in 24 or 25 won´t open, but starting new projects is flawless.

Did installing the Dolby decoder completely fix the problem? 

By @wxthings

[wxthings]

Just fyi, on both of my Win 11 computers, I now have Premiere 25.1 (with the Dolby decoder). After starting Premiere with the "clear cache" option, the MTS clips audio continues to be out of synch from video. However, if I import a project with MTS clips from Premiere 23.6.8 then the clips are in synch.

[Averdahl]

O.k, that was interesting. This happen probably because Pr 23.6.8 conforms the files and create a proper media database that then are used by Pr 25.1 when you import the project. Not sure but almost...

One more thing you can try in Pr 25.1 is to close all projects and go to Edit > Preferences > Media Cache and click the Delete button under Remove Media Cache Files. This will delete the Media Cache Database and will force Premiere Pro 25.1 to re-conform you files again. This often helps.

So when done, try to open a project in Pr 25.1 that you know have files that are out of sync. If it works you probably can skip Pr 23.6.8 in your workflow.

...However, if I import a project with MTS clips from Premiere 23.6.8 then the clips are in synch.

By @wxthings

[wxthings]

When I do that, opening a project in Premiere 25.1 that was created in Premiere 23.6.8 correctly synchs the audio and video in MTS clips, but when I then try to import a new MTS clip into that Premiere 25.1 project, the audio and video continue to be out of synch.