What to use to decode-->re-encode

[RedDwarf1]

Would having a Hi Def (H264) decoding Graphics card be useful when re-encoding H264 1080p video?

I am planning on rebuilding my PC and want to know whether using a graphics card to decode the video would be helpful and avoid having to use CPU time doing the decoding before re-encoding it to 720p.

Is this a viable and workable proposition?

The original H264 1080p would require to be decoded by something (CPU or graphics card) before re-encoding could take place wouldn't it?

So would it be beneficial to offload the decoding to a graphics card rather than using CPU time (which could be fairly significant for 1080p H264 video) which could be better spent on the actual re-encoding?

Is my thinking correct or can anyone shed any light on it?

[cogman]

Thats a definite maybe you have on your hands. I have never had a H.264 decoding video card so I really couldn't tell you if it would help at all. I believe that it would, but that all depends on the codec you are using to decode and if it takes advantage of the video card for decoding.

IMO if the choice is between a quad core and a video card that can decode, get the quad core. And, if at all possible, get a penrynn quad core. If you are already getting one, then I would say that a decoder might help now, but should help in the future (though, we are talking like a 10% increase or so.)

Again, I don't have a vid card capable of decoding H.264 video, but I imagine if the directshow codec you are using works with it, then you should be fine.

[foxyshadis]

If you don't really care about performance and can get one cheap enough, like $50 or less, go for it and the quad core! You can link the decoding and the encoding so that they work hand in hand for a killer speed boost that way. I forget which decoders work only in direct-to-renderer mode and which can do partial (bitstream or mocomp).

[RedDwarf1]

Thanks for your responses.

I was expecting to get a Quad Core CPU, I was not going to avoid getting a decent (Q6600) CPU. I just hoped that having a graphics card such as a nVidia 8500/8600 or maybe an ATI 2400/2600 might help reduce the CPU usage decoding the H264 video so more CPU time could be used encoding to improve the encoding time. I am not too certain about what level of decoding graphics cards can actually do.

I do not play games so I only need one which could help with Hi Def decoding and help encoding times. In fact from the reading I have done so far with regard to nVidia the lower graphics cards such as 8500GT/8600GT/GTS can help with decoding better than the higher end 8800 versions due to an improved graphics core. The new 9 series models just on the verge of being released must also include those additions so they should be just as good but more expensive being newer.

Information on the ATI cards abilities is a lot less well documented. I have no idea what they are capable of, some tests suggest they are better than the nVidia cards but other information say they have limitations on what help they can provide.

But I am sure some hard core video encoder would not overlook any advantage or speed improvement.http://i66.photobucket.com/albums/h276/DianneOnly/wink3.gif