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.

 

[Rich Grise]

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.

How does that "TIVO" work? That is the one, isn't it? Where you can pause
real-time TV and catch up later? I'd think this same technology could be
adapted - what I'm thinking is put the whole shot in memory, and pick and
choose frames at your leisure, although there's a very good chance that I'm
blowing smoke out my ears.

Cheers!
Rich

 

[Scarfie]

How does that "TIVO" work? That is the one, isn't it? Where you can
pause real-time TV and catch up later? I'd think this same technology
could be adapted - what I'm thinking is put the whole shot in memory,
and pick and choose frames at your leisure, although there's a very
good chance that I'm blowing smoke out my ears.

Cheers!
Rich

Smoke is better than nothing...thanks for the reply.

Our old system used MJPEG based hard drive system - it was made for video
professionals with more bells and whistles than Tivo at about ten times the
price (didn't need or want the TV tuner/programming of Tivo). Someone
wrote a control application for it that did the slow motion.

Keep in mind we're hauling this equipment in a cart to all sorts of
locations. It gets pretty cumbersome with multiple hard drive units,
monitors, etc. We recently started using DVD Recorders and LCD monitors
which has lightened the load considerably. Now if we could get the slow
motion capabilities out of the DVD Recorder playback, we would never have
to lug the hard drive system on set again (plus we can spend approx $2000
less on a system with the DVD recorders).

Bypassing the system synch clock of the recorder and inputing our own
signal has to work! A little prog on a PDA or PIC could send the new synch
signal. Would be lightweight and efficient.

Any ideas?

 

[Rich Grise]

Smoke is better than nothing...thanks for the reply.

Our old system used MJPEG based hard drive system - it was made for video
professionals with more bells and whistles than Tivo at about ten times
the
price (didn't need or want the TV tuner/programming of Tivo). Someone
wrote a control application for it that did the slow motion.

Keep in mind we're hauling this equipment in a cart to all sorts of
locations. It gets pretty cumbersome with multiple hard drive units,
monitors, etc. We recently started using DVD Recorders and LCD monitors
which has lightened the load considerably. Now if we could get the slow
motion capabilities out of the DVD Recorder playback, we would never have
to lug the hard drive system on set again (plus we can spend approx $2000
less on a system with the DVD recorders).

Bypassing the system synch clock of the recorder and inputing our own
signal has to work! A little prog on a PDA or PIC could send the new
synch
signal. Would be lightweight and efficient.

Any ideas?

Well, I have no idea how a DVD works, but if it's a data storage medium,
the data can be got out any way you want it, depending how much hacking
you want to do.

First, I need to drag my headbone into the 21st century - isn't a DVD
pretty much just a CD with an order of magnitude or so more storage?

Thanks,
Rich

 

[Scarfie]

Well, I have no idea how a DVD works, but if it's a data storage
medium, the data can be got out any way you want it, depending how
much hacking you want to do.

First, I need to drag my headbone into the 21st century - isn't a DVD
pretty much just a CD with an order of magnitude or so more storage?

Thanks,
Rich

Pretty much the same as CD. The only problem with getting the data out the
way we want it is hacking into the deck's OS or hardware to make it do what
it needs to do.

The system clock...the system clock...just need to override it with another
clock signal...

 

[Electric dabbler]

Pretty much the same as CD. The only problem with getting the data out the
way we want it is hacking into the deck's OS or hardware to make it do what
it needs to do.

The system clock...the system clock...just need to override it with another
clock signal...

Hi,

Sadly this wont be so easy on a DVD player, with CD players it IS possible
to alter the system clock and to some extent alter the
pitch of the audio since the data is clocked off the disc at the same rate
everything is locked to one crystal. So long as the frequency
change wasn't that much the CD player could continue to work just at the
wrong speed!

DVD players also have a master clock, usually about 27MHz (for the PAL
system), the problem is that altering this will alter all the timing in
the player, since the DVD player has to produce a correctly synchronised TV
picture the timing pulses for this will change too...

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.

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

 

[Tam/WB2TT]

Pretty much the same as CD. The only problem with getting the data out
the
way we want it is hacking into the deck's OS or hardware to make it do
what
it needs to do.

The system clock...the system clock...just need to override it with
another
clock signal...

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

 

[Scarfie]

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.

 

[Scarfie]

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.

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.

 

[Tam/WB2TT]

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

 

[Jim Meyer]

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.

Do it all in software like Microsoft does. I've included a URL below.
You may need to cut-n-paste to get it into your browser though.

http://www.microsoft.com/windowsxp/...sing/productdoc/en/toplayadvdinslowmotion.asp

Jim

 

[Electric dabbler]

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

Good point Tam.

This might be the best approach - most DVD players have a 'front panel'
micro which deals with local keyboard and decodes IR commands - this data is
then sent serially to a more complex DVD system processor (very often
combined with the MPEG decoder). Analysing the signals between the two chips
might reveal the control code that you will need to mimic.

Philip