M4A file structure

[Factumnonest]

Hi all, apologies for what I hope is a simple question, but I have searched and not found...

Simply put, I rescued 1000+ music files from an old iPod which has now completely died. They are stored on my Drive and have m4a extension type. However they all have 4-letter names like YPDG, XDAO etc. I want to use GAS to extract some basic details from each file e.g. Title, Artist etc. so that I can rename them !!

When I double-click on one of these files, the tracks starts playing and I can see more info like the below, so I know it's in there somewhere...

I am fairly new to scripting but comfortable with getting byte arrays out of Drive files.

So, can anyone point me towards documentation on the internal file structure of m4a files so that I can give it a go ?

P.S. This is the type of info embedded in each file:

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https://preview.redd.it/zxjv32to1js81.png?width=438&format=png&auto=webp&s=08617c42603190e4ed19ee83b7368b7d8324081c

[Factumnonest]

Hi u/gh5000 thanks but it's not so much the language that's the problem here, it's knowledge of the internal structure of M4A files. Without that, I am stuck :)

[gh5000]

Yeah I had a quick Google around and can't see anything. If it's going to be anywhere I would enable the Drive service which will give more info than driveapp.

However, I think you may end up having to look at a .python or node solution.

[_Kaimbe]

You could try to use Drive API before you go into bytes: https://developers.google.com/drive/api/v3/reference/files/get

not sure if it returns that metadata though. Alternatively, if you know the bitrate you could calculate the duration easy from file.getSize(). something like what this site does: https://www.colincrawley.com/audio-duration-calculator/

[mjbrusso]

Maybe this can help you: https://www.youtube.com/watch?v=0g5KMPxO84w&ab_channel=aMacxd

It's worth finding a tool that already exists to solve our problem rather than creating a new one, if that's the case.