Lets see if I get any of this wrong on the Video Front (as I too am currently building a new Theater Room with 4k AVR, PJ 7.2.4 Dolby Atmos etc). I've got all the AV and PJ equipment but still considering the best approach for the HTPC and Video Sources.
- Decoding a video is relatively straight forward and (unless there are bugs) the results are the same between SW and HW decoders and different devices. They will either support the format or not.
- Scaling the video to fit the resolution of the output device is another beast. There is the requirement to scale the Luma or Image (B&W) part of the image when the source image is not the same as the display (eg say 1080p to 4K). Then there is also the requirement to upsample the Chroma (Colour) part of the image to match the Luma, and as the Colour compentent are normally "
sub-sampled" so they are at a lower resolution than the Luma. Finally there is the conversion to RGB to send to the display devices. There are may different algorithms that can be used to scale both the Luma and Chroma. All have different pros and cons as none of them can accurately create the missing information, and they will take different amounts of computational effort (and it needs to be all done in under the frame rate of the content you are watching, eg 1/24th, 1/50th, 1/60th of a second).
- HW Scalers you are stuck with the algorithms and performance the device has
- SW Scalers (eg PC) are more flexible. You can use your CPU to do these tasks and/or the GPU. Given the GPU are very powerful for image manipulation, we find the the likes of renders such as madVR (used by Red October HQ) allow users to use a wide variety of algorithms to to do the video rendering tasks. The more powerful/faster the GPU the more intensive algorithms you can use.
The hard bit is working out setup gets the output you want. More computational power gives you more choices but if you are happy with the quality from Red October (Std) then any modern PC should be fine. From here you need to add a dedicated GPU to play with higher end settings.
I've for many years built my main HTPC on
Shuttle XPC Barebones as they are smallish, quiet but take a full sized GPU and ODD. You can also just upgrade the GPU if needing more power for the renderer. I've also had pretty good success (but have not tried 4K) with the diminutive
Intel NUCs on moderate settings.
I am also trying to balance the (potential) option of playing UtraHD Blu-Rays from a HTPC, but these have very specific requirements for the CPU, Motherboard, ODD, and SW Player (only Cyberlink PDVD at this stage) in an attempt to prevent piracy. I'm not sure if the Shuttle or NUC will work. Other option is to use a separate UltraHD Player for now (even and X-Box One S).