On 16/08/2005, at 1:23 AM, Justin Binns wrote: > The big technical hurdle here is that you can't get raw video from the > PVR cards, only encoded MPEG-2. In order to use this in VIC, it has > to be decoded first, so it's not just writing an interface (the ivtv > drivers don't even expose V4L, as far as I know), it's also writing an > mpeg2 decoder that works fast enough to feed vic with raw frame data > (for subsequent re-encoding into H.261) without having lag issues in > the video that are less than useful (which is something that will be > difficult, given the minimum GOP issues, but shouldn't be impossible). > So, all around, not impossible, probably, but not a trivial issue.
Justin, Last time I played with the IVTV driver, there was a utility program packaged with it which allowed some control over the card. I recall one of the options allowed setting the GOP length. If that works properly, I had the idea that a GOP = 1 would effectivley be a single jpeg frame - hopefully making the decoding trivial. Haven't tried it yet, of course. So, since you raise "minimum GOP issues", I guess the question is really whether a GOP = 1 is actually possible. If it isn't possible, then you're right that it probably isn't worth persevering with this type of card; even if the the actual mpeg decoding time is so fast that it isn't an issue, the fact that you can't even begin decoding until a group of 12 (or whatever) frames has arrived means the video is always going to be half a second (or whatever) out of whack. chris Christoph Willing Ph: +61 7 3365 8350 QPSF Access Grid Manager University of Queensland
