On Thu, 20 Apr 2006 21:53:58 -0400 (EDT) steve tell <[EMAIL PROTECTED]> wrote: > > The phenomenon appears and disappeares at random positions of the avi > and stays > > for a sequence of frames (sometimes seconds or minutes). When I > recapture the > > movie the changes (problem on/off) appear at different places, but they > appear. > > > This sounds similar to a problem I have with an LML33 (also zoran-based) > card. Sometimes the association of fields into frames would is wrong in > captured video, and piping through "yuvcorrect -T BOTT_FORWARD | > yuvcorrect -T LINE_SWITCH" would fix it. > > But I found that once capture is started, whatever field-frame state the > card started in it would continue solidly for hours. So my workaround is > this: > > - modify lavrec to display the captured video on-screen while recording > - just keep killing and restarting lavec until it starts up correctly > > The right test pattern makes it easy to detect this problem. I found that > the boxy font in the on-screen display of a Horita VITC generator was > perfect. So I enable the display, restart lavrec until its clean, disable > the display and record away. > > I'm always using a stable video source, either directly from a camera or > a surplus industrial TBC in front of an SVHS player. > > Steve
Hi, Steve, Hi Ronald,
Thanks for the answer.
I also tried to readadjust the field-pairing with BOTT_FORWARD+LINE_SWITCH.
It mends the phenomenon, but as I see the phenomenon reappear after some
random time this implies the possibility that we are observing field-drops
here. Not frame-drops, but silent field-drops. When a single field is dropped,
the field-pairing would change. I do not know the driver internals well enough
to know wether silent field-drops are possible.
Ronald, what do you think about this? To me it sounds plausible. The
phenomenon would be the same. Frames composed of incomplete field sequences
like
0123456789 -> 01,23,45,67,89
012.456.89 -> 01,24,56,89
would appear as "2nd field shifted by one line", and after the next field-drop
it would look OK again. (and lavrec maybe inserting one frame for AV-sync?)
Also the temporal sequence of the fields would appear to be right, as I
checked on a video with horizontal motion. It also would explain why I have
been a bit unsure if it is really the 2nd field which shifts. After each 2nd
field-drop the following single frame would appear to be shifted in the 1st
field.
One question remains. Why could this be solved by xawtv as we found out in the
meantime? Maybe Ronald knows it.
Regards,
Ralf
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