# Extensions

**URL:** https://community.mp3tag.de/t/extensions/11772
**Category:** General Discussion
**Created:** [March 25, 2011, 4:08pm UTC](https://community.mp3tag.de/t/extensions/11772 "2011-03-25T16:08:03Z")
**Posts on this page:** 3
**Page:** 1

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### Author: ![auldyin](https://community.mp3tag.de/letter_avatar_proxy/v4/letter/a/b38774/32.png) [@auldyin](https://community.mp3tag.de/u/auldyin)
#### Post date: [March 25, 2011, 4:08pm UTC](https://community.mp3tag.de/t/extensions/11772/1 "2011-03-25T16:08:03Z")

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I have been advised to change MP4 extension to M4A in my collection...(something to do with compatibility in iTunes, iPod).  
Trouble is I have about 4000 MP4 files.  
Can any of you guys tell me how to effect batch changes of this type?

Cheers

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### Author: ![pone](https://community.mp3tag.de/user_avatar/community.mp3tag.de/pone/32/272_2.png) [@pone](https://community.mp3tag.de/u/pone)
#### Post date: [March 25, 2011, 4:27pm UTC](https://community.mp3tag.de/t/extensions/11772/2 "2011-03-25T16:27:09Z")

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> [@auldyin](#):
>
> I have been advised to change MP4 extension to M4A in my collection...(something to do with compatibility in iTunes, iPod).  
> Trouble is I have about 4000 MP4 files.  
> Can any of you guys tell me how to effect batch changes of this type?

Action: **Replace with Regular Expression**  
Field: **\_FILENAME**  
Regular Expression: **.mp4$**  
Replace Matches with: **.m4a**

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<div class="post-metadata">

### Author: ![auldyin](https://community.mp3tag.de/letter_avatar_proxy/v4/letter/a/b38774/32.png) [@auldyin](https://community.mp3tag.de/u/auldyin)
#### Post date: [March 25, 2011, 5:11pm UTC](https://community.mp3tag.de/t/extensions/11772/3 "2011-03-25T17:11:54Z")

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> [@pone](#):
>
> Action: **Replace with Regular Expression**  
> Field: **\_FILENAME**  
> Regular Expression: **.mp4$**  
> Replace Matches with: **.m4a**

Pone, you are a star!!

Thanks