I have a Scientific Atlanta 8300HDC, and I've been using hdmi to watch 1080i no problems, really sharp picture. I recently bought a component rca cable from monoprice, and I hooked up the component to the tv, and I have the setting set to 1080i, and I see a big difference, for the worse.

Why is the picture quality so bad? I've read component should have good picture quality too. Did I get some bad cables?

The difference is in the quality of the color not in the resolution detail. Your SA tuner has to convert the color to analog color for transmission over the component interface and if you have a digital technology TV your TV has to convert the analog color back to digital so be sure that you have updated all of the picture/color settings in your TV that are used for the component connection since they are set and saved separatly from the ones used for your HDMI connection.

The difference is in the quality of the color not in the resolution detail. Your SA tuner has to convert the color to analog color for transmission over the component interface and if you have a digital technology TV your TV has to convert the analog color back to digital so be sure that you have updated all of the picture/color settings in your TV that are used for the component connection since they are set and saved separatly from the ones used for your HDMI connection.

The color is pretty good. But the picture in hdtv channels is grainier and not as sharp. I don't think it is something I can change with color settings. Even when I press guide the channel lineup is more pixelated.

When using my component, the hdtv channels looked like my hdmi regular channels except not as good, the regular channels through component are horrible and snowy.

You didn't mention what kind of TV you had.

As Walford pointed out when you use component the signal has to be converted from digital to analog and back again. That is two opportunities for the signal to be degraded. Some TVs and some STBs are known to have poor component capabilities. In some cases this can be the difference between a SA 8300HD and a TiVo HD, or a Pioneer Plasma and a Westinghouse. *These are general statements, I don't know how good the outputs are on a SA8300HD, or how good the inputs are on a Westy.*

But I do know that on my setup I can't see any difference between component and HDMI. (TiVo Series3 and Pioneer PDP-6010FD)

Did you adjust the settings on your TV for the new input? Most TVs maintain separate brightness, contrast, color, etc. settings for each input and your component input might be far from correct.

Component interconnects are analogue, HDMI is digital.

Your set top box will be receiving a digital signal and will keep this digital for the HDMI output, but will convert it to analogue using digital to analogue converters for component output. This conversion can add noise, and also if the D/A converters and output stages (and in some cases cables) are not highly specified they can have a filtering effect, reducing high frequencies (and in some cases adding ringing on high frequencies)

If you have an LCD, Plasma or DLP display then it will process video in the digital domain, so again, an analogue component signal will have to be converted to digital using an analogue to digital converter. These too can introduce noise (quantisation noise) and the analogue input stages can also add noise, filter high frequencies, introduce ringing etc.

HDMI will normally - everything else being equal - offer a picture that is the same or better than component. It is unusual for component to offer any benefits over HDMI - everything else being equal. (Though the noise introduced by component connections could, in some cases, mask posterisation/banding artefacts inherent in some digital sources so appear to improve things on some content)

I have a new Panasonic PZ plasma. I couldn't deal with component, I switched it back to hdmi output to the tv, and ran component to my receiver. Now I only get one channel output from my receiver. I don't like component. I wish there were 2 hdmi channels on the receiver. My life would be good.