I'm not sure what you mean by "wavy pulsating line". If you're talking
about the bottom of the picture having snow, etc, that's also typical from
VHS bad tapes, bad alignment, etc.
I quess calling them scan lines with no picture might be more accurate. In
place of the picture I get a few rows of color blobs moving across the
screen. Very annoying. I am trying to copy old VHS tapes that were taken
about 8 years ago using my VHS camcorder. I want to put them on DVD. However
that mess across the bottom would be very distracting for a long period of
viewing.
OK, now *THAT* sounds very much like teletext/closed-captioning
type data. Perhaps the camcorder used that sort of stuff for controls?
I've never heard of that.
Also, teletext, etc is supposed to be in the VBI... that's at the
TOP of the screen, not the bottom. Perhaps the vertical sync is somehow
off. If that's the case, you're probably "missing" picture on the top of
the screen. Could be a bad DC-restore somewhere in the loop.
Dunno what you tell you except maybe try a different VCR. IIRC,
there are some "VTR" type heuristic hacks in some of the capture chips.
Maybe those may help... I don't know if ivtv implements any of them on the
saa711xx chip (pvr-250/350) or cxx (pvr-150/500)
ptune? You connecting via the RF-input? You really want to connect
via composite (or s-vid if your VCR is neato enough to have it).
I only have a RF output from my VCR. I use channel 4 to copy them thru my
pvr-250.
Ughh. That adds a little more variables to the equation. Can you
use the camcorder (assuming you still have it).
What would happen if I changed the capture to say 460 lines. Would this cut
off the bottom?
Usually, capturing fewer lines does a "spatial interpolation"
within the capture chip... it still captures the whole frame, just phonies
up a reduced capture size. I remember from reading the datasheets on some
capture chips that they can sometimes be set up to NOT resize, but rather
capture a "window". Again... I don't know if ivtv driver does this.
A quick mucking around in the saa7115 datasheet makes me think it
may be possible.
If you've got persistant fuzz at the bottom, the "crop filter"
suggested would be a post-processing thing once you've recorded it. Without
a more accurate description of the problem, it's hard to figure out what's
causing it.
This appears to be a common problem with VHS. There are others having the
same problem. However no one has suggested a cure. How would I eliminate this
in post processing?
You can definately use a crop-filter (e.g. one in avidemux) in
post-processing. That will, however, require some fairly ugly transcoding
with quality loss. If you're trying to make a DVD-compatible resolution,
you'll need to keep 480 lines (or go to 240... not recommended). That
means either cropping/upscaling which will stretch the picture a bit, OR
not cropping so much as "blacking over" the distracting stuff.
It certainly sounds like a "garbage-in -> garbage-out" thing. The
best way would be to capture it properly in the first place.
-Cory
--
*************************************************************************
* Cory Papenfuss *
* Electrical Engineering candidate Ph.D. graduate student *
* Virginia Polytechnic Institute and State University *
*************************************************************************
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