I don’t want to list the software name here as it might violate rules. You basically load the file and tell it what you want then it does the rest to upscale it to the new quality file.
The AI method RedFox 1 mentions. It’s also not cheap.
Funny that you mentioned this, I'm running a program in the background that's doing upscaling of some Twilight Zone episodes that completed my collection with some episodes that were of lesser resolutions from Archive.org
It's taking about 1 1/2 each hours for each of the 21 files using AI upscaling to 2X 1152x864 size as H265.
I figured out that if you choose 1080 AI upscaling it only uses the GPU on some files in the software but if you choose the 2x option it uses the GPU and the CPU and takes about 1/3 the time and outputs a great version that plays really well on my home system.
It must be that upscaling a video of a non-standard size to 1080p is mathematically different process/algorithm from simply 2X'ing it and has to use the GPU only and isn't written for CPU too.
I did this on one movie that I liked a lot (7 Faces of Dr. Lao - Tony Randall) with a 720x404 Res as 2X (1440x808) and the resulting output is *really* nice and seems like a whole new version with it's clarity and focus.
It's great for breathing new life into some old movies you might have really liked and the output is fantastic.
The AI upscaling is very GPU/CPU intensive and the time will relate to your video card.
I have a RTX 2070 super, it's ok, but I wish I could afford a RTX 3080 or 3090 - maybe next year.
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I just paid $129 to complete my software suite of a product that includes these AI upscaling and AI Smoothing modules.
The kicker is that if you have a friend that owns this product you can get them to buy you full Lifetime suite of all the products that include the AI upscaling/AI Smoothing modules as "A Gift" for $69 and includes a free $30 Amazon gift card, so it's like $39!
I'd do this soon if you're considering due to software companies introducing and moving to subscription based services.
It normally would cost you $259 for the entire suite of lifetime licensed products.
The choices I have of AI upscaling are 1X, 2X, 480p, 720p, 1080p & 4K.
So really a 720p 2x conversion should go to 1440 with about 1/3 the time if you AI Upscaled to 1080p...
Haven't tested this yet on a 720p file (just purchased today) to 2X vs 1080 for time yet, but I did do a test of Cocoon that I had as 856x464 to 1080p that took over 8 1/2 hours!
Cocoon 856x464 AI upscaled to 2X size took 1/3 the time as doing it to 1080p because it used GPU *and* CPU on my RTX 2070 Super.
I'll probably only use the 2X for now and 1080p (when I get a better Graphics card 3080 or 3090) due to conversion time.
Mike