Hi!
I know that this is not 100% the right forum for this type of problem. But
as freevo still acts mainly as a TV receiving / recording solution, I post
it here. I thought getting TV working as perfect as a TV usually does
shouldn't be a big problem, but after investing some time I now know it is.
Probably someone can comment on this (I maybe wrong with the issues).
The following problems occur in general when capturing TV on a PC. I
assume that your display uses
1. TEARING
Tearing occurs whenever switching to a new frame isn't synchronized
to the vertical blank trace. The upper half then shows the old, the lower
one the new frame.
2. INTERLACED / PROGRESSIVE SCAN
TV pictures are still being broadcasted using interlaced PAL or NTSC
formats. In order to view them on our progressive scan display we have
to deinterlace it, i.e. merge top and lower field pictures into a full
resolution frame.
3. JUMPYNESS
If your display's refresh rate does not EXACTLY match the frame rate
of the broadcasted signal you see jumpy movements.
The first two issues are farely easy to solved and programs like tvtime
do their best to not let you know that they've ever been present. The last
one however can definitely be a show killer as it makes fast scrolltexts
almost unreadable.
I can imagine at least two solutions:
1. Set your refresh rate to almost the refresh rate of the incoming signal
and pass the vsync of the incoming signal to the graphics card. This
maybe hard or even impossible to realize, but it would be a solution
that does not require any additional CPU time. It is almost what a
traditional TV set does.
2. Interpolate two input frames in a row to form a single output frame.
This will however introduce some smearing in case of fast movements,
but they should be smooth again.
I don't know if anyone of you are 100% satisfied with the current solutions
available for PCs (under Linux), but at least for the annoying jumping
pictures I didn't find any solution.
I would appreciate your comments.
Cheers,
Stephan
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