Guess I thought this would be an easy plug and play since all my stuff runs through the rec. and is output to TV (Samsung DLP 4674), but perhaps not
Definitely not, there's nothing about sending audio and video from a Mac (any Mac let alone a 7 year old G4) through an AVR and then to an HDTV that has ever been plug and play. But back when I had a G4 mini I can tell you it connected just fine to a Samsung DLP 4663, which was 720p native res just like yours, and did a decent
job with standard def dvd rips. I tried it over VGA, DVI to DVI and DVI to HDMI, and all worked just fine at 720p when directly connected. I used an M-Audio Firewire Solo in order to get DD 5.1 and DTS passthrough to my AVR and that worked most of the time, it was a huge improvement over going analog audio out of the mini. It's just sooo vastly under-powered, as soon as I could replace it with something that had an Intel core duo, I did.
As far as why do this at all . . . . just figured I'd get some use out of it--- Amazon video streaming, web surf, etc. Not much, but at least not sitting on a shelf doing nothing. For an out-dated machine, it still works well.
well, video streaming is actually somewhat demanding since it involves Flash or, the lesser of two evils, SilverLight, so Amazon, Netflix, Hulu et al requires a pretty powerful, relatively modern Mac, for any decent performance, at minimum a 2.0 C2D Intel. Just about the only thing that G4 mini would still be good for would be a very low priority bedroom HTPC, where you'd be watching on a smaller screen, say a 32" 720p set, and where you'd only be watching standard def rips. You'd still have to go analog audio out, but most older sets have an analog audio in option.
That G4 mini would also serve quite nicely as a quiet, low power whole house iTunes audio server for your other devices and Macs, if I still had one lying around and hadn't already set something else up for iTunes home sharing (in my case, that's how I repurposed a 2.3 dual G5 PowerMac) so that's how I'd recommend you use it. I'm totally with you on not just letting older stuff lie idle. The problem you'd run into even just using it for iTunes music playback directly connected to your AVR for audio only is you wouldn't have a digital audio out...and its analog audio out over the minijack would be relatively poor. Now, put an Apple TV or Airport Express there instead and let them pull iTunes content from that G4 mini acting as a server and you'd be all set.