GPI specs

[Tony Lorentzen]

Does anyone know if there's any speed limitation on the GPI? What I'm asking is - could I set up an external mechanism to trigger the camera 24 times per second.

Also - what kind of delay is there between triggering the pin and the camera actually recording the frame.

What are the viewing possibilities when using the GPI - could the monitor be set up to show the last recorded frame?

 

[wedowee]

And why doesn't variable speed go up to 120fps when ramping in camera?

 

[Tony Lorentzen]

Could someone from RED please respond to this question. This is a question I'd like to be able to answer for a client.

 

[Stuart English]

External Trigger

External Trigger

An external trigger won't run the camera at anywhere near 24 fps as the GPIO has a fair amount of latency.

I'd guess more like 6 to 12 fps using that technique.

The camera always displays what its looking at - not the recorded frame - unless its in playback mode.

 

[CVB]

Hey Stuart, is it in the cards to have it work faster in the future?

 

[wedowee]

I see the ViewFactor guy chiming in. I was looking for an answer to this question before purchasing the Origo by ViewFactor. Is it a camera limitation of about 6 to 12 fps on ramping, or a trigger cable limitation?

 

[Tony Lorentzen]

An external trigger won't run the camera at anywhere near 24 fps as the GPIO has a fair amount of latency.

I'd guess more like 6 to 12 fps using that technique.

The camera always displays what its looking at - not the recorded frame - unless its in playback mode.

Thanks Stuart. So in order to get the camera to sync up to "something external" I'd have to use the genlock interface?

 

[Andrew Young]

Hi Tony,

We've been doing extensive testing with my Red camera on one of DuArt's optical printers, using the printer to fire the Red when the film is in the correct position. Speed, of course, is one of our many concerns.

I'd guess more like 6 to 12 fps using that technique.

It would be fantastic if we got frame rates like those Stuart mentioned above. However, we have been unable to get reliable performance at more than 50 frames per minute. The trigger certainly does work faster than that but we have discovered that the latency is variable, so that for example, when shooting at 2 fps, in very minute or so of footage there will be a frame that fired late, ruining the transfer. So for critical sync, we've had to stick to speeds just below 1 fps, which is much slower then we had hoped. Maybe this is something that will improve in future builds, but we have not gotten any word from Red on this.

 

[CVB]

I see the ViewFactor guy chiming in. I was looking for an answer to this question before purchasing the Origo by ViewFactor. Is it a camera limitation of about 6 to 12 fps on ramping, or a trigger cable limitation?

The limitation is when you are using an external trigger to control the frame rate of the camera, ie sending 24 pulses per second to the camera to get 24 frames per second. This issue does not affect ramping capabilities as that is done internally by the camera.

 

[Tony Lorentzen]

Thanks for your feedback Andy. Have you considered trying to sync up the camera via Genlock instead of triggering the camera?

 

[electrodist]

Anymore news on this topic? I imagine the latency is caused by the recording media being to slow to keep up with the in/out demands of triggered capture.

 

[Axel Mertes]

Here is an excerpt of an email I got regarding the same topic:

> Here are the answers that I received from Stuart.
>
> Sean
> ------ Forwarded Message
> From: stuart <stuart@red.com>
> Date: Thu, 13 Mar 2008 12:54:28 -0700
> To: Sean Ruggeri <sean@red.com>
> Subject: Re: ------------- Urgent question on GPIO for tomorrow shooting
> ------------------
>
>> [...]
>> Further we would like to know if its technically possible to external
>> trigger up to the recording limits of the camera, ie. if it can
>> shoot 2K @
>> 120Hz, could we manage to trigger with an external up to 120Hz pulse
>> signal
>> a recording in 120Hz, or is there a technical reason that it would
>> not be
>> possible.
>
> No. But I have not tested the latency...


So in this Email we got the hope that it would be possible to go "near" realtime capabilities. But apparently this seem to be impossible now?

My question is:
Is that technically IMPOSSIBLE for the RED ONE, or would there be another chance to implement this, e.g. using the USB interface instead of that stupid GPIO?

Any insights from RED would be really helpful in this moment!

Regards,
Axel

 

[Axel Mertes]

One more point and one BIG wish:

We want to trigger strobo flash lights for extreme lighting situations using the camera as sync signal source.

We want to shoot with Varispeed, so anything between 1 to 120 Hz is thinkable.

As we see it would not work when the GPI isn't fast enough.

But would it be possible to add following function to a new firmware release:

- send a GPO signal flank per each frame shot by the RED ONE camera

Right now we get a GPO signal per each time the record button is pressed.
But we want a signal, perfectly in sync and with nearly no latency, that tells us when the RED ONE is exposing a frame (because otherwise the strobe flash would be out of sync).

Is that possible?

I am not aware that we can use any outputs for this right now.
The HD-SDI signals are reclocked, especially in Varispeed modes. So they are useless.
The Genlock is input only.

Stuart?

Anyone else?

Thanks,
Axel