When you’re burning a CD or DVD, the computer isn’t typically the weakest link; it’s the CD/DVD burner. When they write, CD/DVD burners operate at some maximum speed of rotation and how quickly a burner spins depends on its hardware and how fast it can write the data to that disc.
But I think something else might be going on here. You mentioned that your original video is in MP4 format. That’s not a format that is written to DVD.
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Writing to DVD
DVD format is definitely encoded and compressed, and sometimes encrypted, but it’s a different format. It’s certainly a very different format from MP4.
In your case, the DVD-burning operation may have taken a long time because the computer’s processor had to first convert it from one video format to the other. That can be a very CPU-intensive operation. In fact video conversion is often used as an example of a process that demands a lot from a computer’s CPU.
If that is the limiting factor, then a new computer with a faster processor might well be the answer. Depending on the video conversion software being used a multi-core processor can sometimes dramatically reduce the amount of time that the conversion process takes.
Again, that depends on the specifics of your current CPU: how fast it is, how much RAM you have, and how fast your disk is. Your current computer may already be able to handle the conversion process and a new computer won’t make that much of a difference.
If it’s not the conversion process, then it is the speed of the drive that’s limiting how quickly the bits can actually get written. You may want to try burning another type of file (say any type of files to create a data CD or DVD) to make sure that it’s not the drive.
But I strongly suspect from your description that it’s the conversion process.