decode some pixels of 4k video as 1080p

Question

I developed an application which is running on windows OS. This application is decoding incoming video streams and displays on the screen. Lets say I have one 4K monitor and application will display 4 4K streams on that monitor, so every stream will be displayed as 1080p. Decoding 4 4K streams and scaling them to 1080p to display is consuming many resources, especially decoding part even for decoding with GPU. Is it possible to decode some pixels (like every 1 of 4 pixel) of 4K stream then interpolating it to 1080p video? Or is there any other way that will consume less resource while decoding many 4K streams? (I am using ffmpeg for decoding purposes)

Answer 1

Is it possible to decode some pixels (like every 1 of 4 pixel) of 4K stream then interpolating it to 1080p video?

No, that’s not possible, video is compressed by transforming it from the spacial domain to the frequency domain. The resulting video bitstream does not even contain pixels Decoding is the process of reversing this operation. It is impossible (or at least impractical) to resample something while in he frequency domain, it must be converted back the the spacial domain first.

Or is there any other way that will consume less resource while decoding many 4K streams?

Use a hardware decoder, like nvdec, or quicksync if it is available on the video card of the computer.