I was testing this idea.
You also need a link if a QR code goes to a web video. Not needed if you are pointing a phone at an eink or paper book or LCD screen on a tablet or PC. But certainly my phone or tablet can't use a QR code in an app, PDF or ebook. It can only use one on something else.
So if you just want videos, you can create a YouTube channel and put a QR code in paper book and ebook. Then point phone or tablet at it. The QR code is only an image, so can also be a link, and ought to have a caption with a link, then when you read the ebook on a phone or tablet instead of paper or ink, you tap the caption or the image. Some apps zoom image, hence best to have a caption too. Anyway, a QR code should ALWAYS have an honest caption.
My phone's QR reader is set to preview with options to open link, copy to clipboard or open a text editor (or other default app for text, could be Contacts).
I was once tempted to replace the QR codes on Tesco vegetables and some posters with alternate QR codes. It's stupidity that some phones automatically go to a web site and shortened URLs are an evil invented for Twitter that are no longer needed. Twitter does it automatically now.