@edh: I meant to "switch off" the graphic card/gpu the same way you would spin down a hard drive when data is not accessed for a while. After, say, 2 hours without any mouse movement or keyboard input, I wish the graphic adapter to stop processing/preparing the image and supplying it to the monitor. I would like it to switch all "switchable" internal components off (GPU, memory chips, whatever), and stop draining the power in a system and creating unnecessary heat as much as possible.
When talking about audio I didn't have transcoding tasks in mind. I thought about playing the video, in media player of sort. It seems pointless if audio is being decoded while sound output is muted in a player. The modern PC is fast enough and sound data is "packets" based, so starting the decoding/playback process again when sound is unmuted shouldn't be an issue.
@Pappnaas: Yes, my GPU isn't new. But it is one of the very good (efficiency) performers even in today's terms. I found this site (
http://www.behardware.com/art/imprimer/781/) which measured it's power consumption at 7.7W idle-2D and 9.9W decoding HD H264 Video. Those would be all the power modes it will be using in my computer anyway.
My PC is Full-HD capable unit although very low-end, as I tend to reuse as many old components as possible. It has it's strongpoints
-67W TDP CnQ enabled Athlon 64 3500+, one of the faster single-core CPUs (sadly, I can't go for 45W AM2 A64 models at the moment)
-Sapphire Radeon 4350 (H264 decoder keeping the CPU in lower-power states as often as possible. I would have selected some later series as I wish to have XVID videos GPU decoded too, but the rest of the system imposed the limit below Radeon 5000 series)
-Corsair XMS 2x1GB DDR400 ram, CAS Latency 2 and dual channel
-Samsung 22inch Full-HD LED DVI monitor consuming about 16.8W at my settings
and weakpoints
-nForce4 chipset - the spaceheater! (chosen for compatibility reasons as I have 3 IDE optical units plus an IDE hard-drive)
-WinFast-Foxconn mobo (not the most respected brand, but good for as long as it is usable (3+ years in my setup and counting, bought secondhand)
-Rexpower PSU 350W reused from an old Duron1200 SDRAM machine, now requiring overhaul after about 8.5 years of (often heavy) use (occasional whines on load present today, probably because of semi-dry condensers which I plan to replace myself).
The computer is good as-is and I plan to keep it for a while as it gives quite a reasonable economy and decent everyday performance for it's low price. Any substantial upgrade would require significant investment (in new ram chips, new (and very expensive) PSU, compatibility add-on card for IDE devices or (worse yet) new optical devices and a hard drive which are mostly out of the question, etc etc.).