I recently bought a Optoma ES522 HD Compatible Portable DLP Projector but the inputs it has are VGA, Svideo and the standard yellow (video) red/white (audio).
I can plug in my set-top box into it using the one video cable and two audio cables but will this display HDTV? I don't think so but I could be wrong. Do I really need to get a converter box to have hdmi to converted to analog vga in order to get a high def image?
Your projector has a maximum resolution of 800 by 600 so it will not actually display an HD source in HD. It is also a 4:3 panel so the actual resolution is SD with a 16:9 aspect HD signal. It is called hd compatible but that means it will down convert the signal to SD. According to the specs it should have a component video input. That you can use with a set top box or older Bluray player that outputs 720p on the component outputs (newer players do not do this).
I think you may be mistaken. It says my native resolution is 800x600 but the max is 1920x1200. Shouldn't it be able to project a high def image? For the inputs it only has one component input for video as in a single wire and two others for audio. On my LG plasma when I use component there are three wires just for the video and then two additional for the audio. This is why I have doubts because I didn't think a single component wire could transmit HD.