Replacing DVD player time synch / Slow Motion

[Scarfie]

I'm looking for a way to play back DVD video in precise slow motion. The
regular slow motion settings are OK but our needs are more precise.

We use DVD to record video for film. When a scene is filmed in slow motion
we need to replicate the look and feel in the video playback. IE - the
film camera may be overcranked to 36fps instead of 24fps. This will make
the resulting picture play at .67 regular speed. The video we record will
be regular 30 fps (29.97) but we have to play it back with the same
percentage of slow motion. The frame rates used in film vary widely and we
need to match them.

I've already looked into a computer emitting several Frame Advance remote
contol commands per second but it looks like the best we can expect to
achieve is 12 frames per second given the limitations of the remote control
protocol.

My next idea, and the reason I am posting here, is to see if it is possible
to 'hack' into the decks synch generator to feed it time synch from an
outside source. A mini jack or 1/4" jack could be added to the back panel
to input the source synch.

The outside source would be any computer (laptop, specially programmed PIC,
etc) that could modulate the time so the player thinks a second is longer
than a second really is.

Anyone know if this is feasible? I'm willing to offer up a player for
experimentation if anyone can even say it may be possible.

 

[Scarfie]

"Electric dabbler" <no.spam@microsoft.com> wrote in
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"Scarfie" <chris@csmediapro.com> wrote in message
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Rich Grise <null@example.net> wrote in
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What you require is almost certainly possible, you would need to find
a way to modify the way the MPEG decoder behaves so that it repeats
frames many times until you are ready for the next one, thereby
creating a slow motion effect. Of course the servo would need to be
controlled also to keep the read buffer topped up . If you can find a
consumer DVD player that uses a chipset that is documented by the
semiconductor manufacturer
it might just be possible but quite extensive knowledge of programming
would be required.

I think the more I look into it, the more I'm leaning toward building a
simple capture/playback box that can do the slow motion independent of
the DVD Recorder/Player. I'd love to have all the functionality in one
deck but if I have to do it this way, I can make it small and light
enough to haul around.

Another option might be to use a DVD player that is based around a PC
DVD-ROM drive, these were quite common in the early days of DVD, it
might be possible to modify the control data going to the IDE
interface so that frames are repeated, I suspect that the MPEG decoder
would get upset about this
simplistic approach.

What about an 'industrial' DVD player with RS232 control?

http://www.colinbroad.com/cbsoft/manuals/p2DVD.pdf

Just a few thoughts,

Philip

Good thought but those decks are too pricey, heavy, and bulky for us to
cart around. The beauty of the $300 DVD Recorders is that they are
pretty good with wear and tear and if one does crap out, replacing it is
inexpensive compared to the $2500 hard drive system we were using before.

Thanks for helping out on this.

 

[Tam/WB2TT]

"Scarfie" <chris@csmediapro.com> wrote in message
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"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in
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"Scarfie" <chris@csmediapro.com> wrote in message
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Rich Grise <null@example.net> wrote in
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Just a thought, but if you can identify the remote control decoder,
you might be able to identify the output that causes a frame advance.
If you put the DVD in freeze frame mode, and then feed it frame
advance pulses(?) from an external source, that might work. Forget
about changing the master oscillator, that would result in a video
signal that won't play on any TV known to man.

Tam

This was my first thought and I've done quite a bit of digging on the
subject. Turns out the remote protocol will only allow somewhere around
twelve commands per second...at best.

I didn't mean to hack the remote unit. Do it to the decoder output inside
the DVD player, at the point after the protocol.

Tam

The protocol requires that a command signal be sent five times before the
device will accept it. Add in the millisecond delays between the start
and
stop bits and the bits of code, it all adds up. Unfortunately it won't
allow up to 30 commands per second.

Unless someone has a second opinion on this, I'll be trying to come up
with
another solution. Thanks for the reply.