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MP4 BPM 'tmpo' Tag
liamk23PostMarch 18, 2023, 23:16
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April 14, 2017, 15:43
Normal topicMP4 BPM 'tmpo' Tag

Hi, hope you are well. 🙂

I use a number of DJ applications and without going into loads of details (unless you need me to), I am struggling to copy the 'TBPM' tag to the MP4 tag 'tmpo'.

I have created an action for copying 'com.apple.iTunes:initialkey' to 'com.apple.iTunes:KEY', this works great.
I then duplicated this for the BPM but Yate adds the prefix 'com.apple.iTunes' so the result is 'com.apple.iTunes:tmpo'. Other software I am using will not recognise this field as the BPM, it needs to be just 'tmpo'.

Hopefully that makes sense. Please can you help on how to achieve this? Thank you 🙂
2MR2PostMarch 19, 2023, 09:52
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August 23, 2012, 19:27
Normal topicMP4 BPM

Firstly you do not need an action to write the key to com.apple.iTunes.KEY ... there's a setting for it. Preferences - Audio - MPEG4 - Map initial key to. The choices are initialKey and KEY. There is also a setting to enable the reading of both (recommended).

As far as the BPM field goes, it is written to the tmpo atom (no com.apple.iTunes). TBPM is the ID3 frame which is not used in MPEG-4 files. You can verify that tmpo is written by doing a View>Raw Data on any MPEG-4 file which has a BPM value. For all audio types there can be a second BPM tag written named FPBM or com.apple.iTunes:fBPM. This is only used if there is a fractional BPM specified and the standard BPM tag is still written.

Am I missing something?
liamk23PostMarch 19, 2023, 10:38
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Posts: 20
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April 14, 2017, 15:43
Normal topicMP4 BPM

The issue is in the other software, it is coded to read/write com.apple.iTunes:KEY where as other software I use all uses initialkey. The action simply copies the initialkey to KEY so it can be seen in the other software. I will never change the key so it's ok.

I understand what you say about the BPM field, there must be a bug in this other software that means it is not displaying the BPM for MP4 files, no idea why as I have had a look at the code and it appears it is looking for the tmpo tag. I confirmed in Yate that I can in fact see the tmpo tag is written.

Thank you for helping me pinpoint the problem! It's certainly not a Yate issue, I just end up using Yate to fix all my problems. 🙂 Awesome software!
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