They are called Video Processors and you found the correct forum.
To get you started, a couple of the more popular VPs that are currently available are the DVDO Edge, DVDO Duo, and the entire Lumagen line.
Audiosceptics accept audio trials using 25 people. A recent Oxford study with over 353,000 patient records from 639 separate clinical trials shows for every 1,000 people taking diclofenac or ibuprofen there would be 3 additional heart attacks, 4 more cases of heart failure and 1 death every year.
The question is a bit vague but it seems to be asking about a simple format transcoder box rather than a full-featured vp. There are composite and S-video to HDMI and component to HDMI 'converter' boxes that come up in Google but none have all three that I see on the first page. Also it'd be better to explain exactly what it's needed for as transcoding can be done in all HDMI AVRs.
Here's my dilemma.
I want to replace my aging DELL 2405fpw (had it since 2006) with a newer energy efficient LED monitor. My 2405fpw has all the video input connections I mentioned above except HDMI since it didn't exist at the time.
Now, I'm a huge fan of old school gaming consoles and have been collecting them since I was a kid. All of those inputs on my monitor are occupied by game consoles; every thing from the original Nintendo to Sega Saturn to GameCube, I own nearly all of them and play them on a weekly basis.
Naturally, if I'm going to replace my monitor, I would like one that has Composite, Component, and S-Video input, just like my current monitor. The problem is, the only led monitors I've found that have all of those inputs cost $600+.
Since there are single adapters you can buy for hooking up consoles like a PS2 to a monitor, I was hoping there might of been a multi-input box solution instead of having to buy an adapter for each console.