BT878-based cards to not have a comb filter and rely on a notch filter to separate luma and chroma. That means that for any composite input signal (NOT S-vid), they're limited to about 3MHz of luminance resolution. That translates into 352x480 capture. Anything over that is wasted space. Again, if used for s-vid, that is not the case.I've noticed a few things from these settings and from watching this discussion. First of all while the dark scenes are definitely better I notice that when the scene is moving fast I now get interlaced type lines showing up. Am I correct in assuming then that I should not be selecting interlaced because my card is only able to capture at 240 lines so its actually only capturing every other line anyways? Incidentally my card is a bt878 variant I believe (I may upgrade to a PVR250 at some point but not right now).
Is there any point for me to do a higher resolution on this card? Paul
So to answer your interlaced question, you definately should capture more than 240 lines. Getting interlacing lines is just part of the deal when capturing actual video signals.... they *ARE* interlaced. Depending on the content, they can be deinterlaced to some degree or other. If you're not playing it on a computer or progressive tv, however, it's not even necessary.
As far as the PVR-250 goes, that's a big advantage as far as I'm concerned over the bt8x8-based cards. It's got a comb filter, so better Y/C separation. I've measured actual improvements with test patterns up to about 520x480 on a PVR-250 (vs. 352x480 for bt878). The cx88-based cards also alegedly do, but I've never played with one.
-Cory
************************************************************************* * Cory Papenfuss * * Electrical Engineering candidate Ph.D. graduate student * * Virginia Polytechnic Institute and State University * *************************************************************************
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