How can you transcode media to higher bitrates when there is no new information to be included?
In: Technology
There is some upsampling rule to “fill in” the missing information, which often means adding no information at all.
For instance, say you have a bitmap image encoded with a color depth of 8 bits. That is, each pixel is encoded with an 8-bit code that says which of 256 possible colors it is. Now you save this image as a 24-bit bitmap instead. The pixels will still be limited to the original palet of 256 colors. Each of these 256 colors has a corresponding 24-bit code that encodes the same color. You just won’t be using any of the other 16+ million codes/colors that are available at this higher color depth.
Or, suppose you take a 100*100 pixel image and save it as a 200*200 pixel image instead. Every pixel then becomes a block of 2*2 pixels, and the simplest way to do this is simply to copy the value of the original pixel to the new 2*2 pixels. This doesn’t actually improve the image quality (or add information) – it just takes up more space. There are more sophisticated ways of upsampling, these days even using neural nets to make intelligent guesses about the missing information, but it will always be a guess.
It’s a bit like paying somebody $100 in dimes, vs. paying them in $50-bills. It’s the same amount, just using unnecessarily many coins. But using dimes you can in principle pay more precise sums, e.g. $100.20, which you can’t when using large bills.
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