Re: [AG-TECH] Has Anyone got the WinTV PVR 150 to work with VIC?

[Christoph Willing <willing@itee.uq.edu.au>]

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