iPod Transferring HD video purchased on one computer to another

I have checked the forums and couldn't find an answer to this question:

I want to make a purchase on my MacBook of some HD video from iTunes whilst at work (don't want to eat into my available data transfer at home). With regular video it's easy to transfer the videos to my iTunes at home (transfer to iPhone at work --> transfer purchases to iTunes at home), simple, but with HD video, iTunes transfers a standard definition copy to your iPhone, but how do I transfer the complete download (HD and Standard) from my MacBook iTunes to my Mac Mini iTunes without going through a bunch of DVDs. Unfortunately iTunes only allows backup to DVD/CD.

Many thanks

SilentPanda said:

If you right click the file in iTunes you should be able to choose "Show in Finder". You can then copy that file to a portable drive (probably not your iPhone unless you've jailbroken it) then when you get home, drag it into iTunes.

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And as long as my home iTunes is authorized then it should be okay, right? That's what I thought but I couldn't find a definitive answer anywhere. Everything just talks about transferring purchases from your iPhone/iPod.

Thanks SilentPanda