Interlaced UVC Camera

Hello,
I'm using custom hardware (TVP5147 & LPC3131) to build a PAL video grabber using UVC drivers.
The PAL video as standard sends one field per frame at twice the framerate, so while the video stream has an eventual framerate of 768x576@25fps the stream appears as 768x288@50fps.

The UVC spec is supposed to support this one field per sample stream, but I can't seem to make it work on Windows or Linux, changing the interlaced flags in the Class-specific VS Format Descriptor seems to make no difference whatsoever.

I would think I should be able to feed this video stream into a weave deinterlacer to get my full frame back (I don't care about the jagged edges, we actually use them for movement detection), but I can't find any way to achieve this.

Unfortunately I don't have enough ram in my hardware to manually weave the lines, as I would need at minimum a half frame buffer to hold the first field while I wait for the second, then stitch them together, I don't even have a 1/4 of the ram I would need for this. More likely I would need to buffer two full frames, assembling one while I'm sending the second. I would much rather not have to add these extra parts to the hardware when I would think it should be possible to fix this on the pc side.

Can anyone make any suggestions?
Thanks,
Andrew

The key point is that how to change the interlace mode to progressive.
I think you can not use the traditional video decoder.

One Taiwan ic design house " TSSi " had develop the "TS2713"..
This ic can let "interlace" become " progressive"

I had already finished the UVC grabber card.
If you are interested in it, please kindly see my website.

You can search " febon UVC grabber" in google to get more information.

But I wrote in Chinese.