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O2 Framedrops

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Kurt Volker Krieg

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Jan 27, 2002, 3:38:15 PM1/27/02
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Hi,

I've just upgraded my O2 with an A/V Board.
When I record a movie with dmrecord or mediarecorder via composite in, it
occasionally drops 1 or two frames. Sometimes it seems like that it looses
sync on the video signal, so that within the movie it seems that 2 frames
are shown simultaniously. This is when capturing from a VCR. Works like a
charm with a signal coming from a satelite receiver.

Any ideas?

SkyWriter

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Jan 27, 2002, 4:05:46 PM1/27/02
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Kurt Volker Krieg wrote:

> Hi,
>
> I've just upgraded my O2 with an A/V Board.
> When I record a movie with dmrecord or mediarecorder via composite in, it
> occasionally drops 1 or two frames. Sometimes it seems like that it looses
> sync on the video signal, so that within the movie it seems that 2 frames
> are shown simultaniously.

I believe that when it does drop a frame it duplicates the previous frame.

> This is when capturing from a VCR. Works like a
> charm with a signal coming from a satelite receiver.

try less quality when capturing.

>
> Any ideas?

Avi Bercovich

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Jan 28, 2002, 1:44:42 AM1/28/02
to

Nope, but I;d like to add that I've seen similir things happen on my
O2's (but r5k and r10k) when recording from VHS VCR tapes. No problems
what so ever when using a DVD player. (other than the known 6.5.14
(m)jpeg issues)

ttfn,

avi

Michael Rice

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Jan 27, 2002, 4:49:12 PM1/27/02
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Kurt Volker Krieg wrote:

The issue of dropping frames is addressed in the mediarecorded(1) man
page. It specifically mentions that recording from a VHS may degrade the
video signal enough to cause frame drops. It also offers some potential
solutions.

When a frame is dropped, the previous video frames are repeated. So you
end up with a slight (and hopefully very short) loss of motion when
you playback the recording.

Michael Rice

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Jan 27, 2002, 4:54:55 PM1/27/02
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Michael Rice wrote:
<snip>

>
> The issue of dropping frames is addressed in the mediarecorded(1) man

Should be "... mediarecorder(1) man..."

mike

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Jan 27, 2002, 10:46:34 PM1/27/02
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Avi Bercovich wrote:

Same problem here - recording from VCR seems to give me many problems - either
the tape is old and jerky in a few spots and always results in dropped frames
(for example - me trying to capture old gijoe cartoon movies from VCR tapes
that are like 20 years old) or there was a spot where the screen turned white
from dark real quick - for example - a recording of my band playing a club
(dark lighting) where people where using flash photography - always dropped
frames in the same spot of great flashes.
same results if I use dmrecord or mediaplayer. I can not capture anything if
the frames are dropped - once a frame drops, the rest of the movie/caputre is
basically ruined - I see two frames interposed together for the rest of the
movie, or I see strange horizontal lines transposed through out the rest of the
movie. This seems to happen 99% of the time after a frame is dropped and I
keep recording. I thought I might have a bad A/V module - but now I dunno...
(I was planning on making a web site about capturing video with o2's and
various ways around these problems... I still might do that).

There seems to be two solutions to recording from VCR that I havent tried. One
would be to use a device called a TBC, (time based correction ?) which would
help the o2 capture video with a stabilized sync.
The other method that might work is plug up another video device between the
VCR and the o2 (kinda like a TBC, but not a TBC) so even though the signal gets
degraded, the lower voltage might not mess up the o2 to the point where it
losses sync and drops a frame. I havent tried any of these two methods yet,
but any out there - please comment!! :)

I probably wont try a TBC because I hear they are too expensive for a hobbyist
like myself :)

cheers!
mike

Emmanuel Florac

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Jan 28, 2002, 5:03:38 AM1/28/02
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Dans l'article <3C54CE7F...@comcast.net>, mmil...@comcast.net a
dit...

>
> There seems to be two solutions to recording from VCR that I havent tried. One
> would be to use a device called a TBC, (time based correction ?) which would
> help the o2 capture video with a stabilized sync.

TBC = Time Base Corrector. It is intended to correct exactly this kind of
problems...

> The other method that might work is plug up another video device between the
> VCR and the o2 (kinda like a TBC, but not a TBC) so even though the signal gets
> degraded, the lower voltage might not mess up the o2 to the point where it
> losses sync and drops a frame. I havent tried any of these two methods yet,
> but any out there - please comment!! :)
>

Professional VTRs (Betacam SP BVW series...) have a built-in TBC, so
passing thru it corrects the signal. Some professional VHS VTRs from JVC
also have it.

--
-------------------------------------------------------------------------
Emmanuel Florac | Kreode technologies
-------------------------------------------------------------------------

Martin Slaney

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Jan 27, 2002, 7:32:37 PM1/27/02
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Avi Bercovich wrote:

Sure - thats to be expected. A VHS machine is likely to output some pretty wacky
unstable sync signals. If you play in the VHS via a TBC (time-base corrector)
you'll likely find its perfect .....

Alexis Cousein

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Jan 28, 2002, 6:15:41 AM1/28/02
to Kurt Volker Krieg
Kurt Volker Krieg wrote:

> This is when capturing from a VCR. Works like a
> charm with a signal coming from a satelite receiver.
>

That would suggest you need a timebase corrector to get a clean

signal from the source that doesn't work.

Incidentally, try to see if changing the "VTR mode" and "Auto Gain"
buttons on the Video Control Panel's Svideo Input-Signal panel
helps (sometimes changing aperture and bandpass freq. helps, too).

--
<these messages express my own views, not those of my employer>
Alexis Cousein Senior Systems Engineer
SGI Belgium and Luxemburg a...@brussels.sgi.com

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