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Optical Flow in Sony Vegas: How Does It Work?

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Jeremy Rasnic
Optical Flow in Sony Vegas: How Does It Work?
on Jan 3, 2011 at 3:13:35 pm

I have some footage of my son playing on his new power wheels four wheeler that was given to him by his "grand pappy". I was going to post his first time riding it online for family to see, but instead of a 20 minute video I wanted to speed it up.

I open optical flow from Borisfx and set my parameters (I actually only change it from a velocity of 100 to 500 and from upper to progressive for field order) and leave everything else as it is.

I see that my entire event is still on the timeline but the area that no longer exists is now just black frames with the audio still the same length. No problem really, I find the last frame where video still exists and I split the event at that point. I then realize that my video footage has been speed up yet again due to the split. This is not the desired effect I am going for and seeing how I am not using Premiere Pro or Final Cut, the help file doesn't really apply to me as a Vegas user so it is of no help concerning this issue.

Here are my questions:
1. How do I utilize optical flow to speed up a clip 5 fold and trim the resulting blank "slug"?
2. How do I get the audio to equal the length of the video event (like when you do a control drag from within Vegas)?

I know using optical flow is probably overkill for this particular home movie, but I wanted to try it out before I actually needed to use it on a real project... glad I did.

j razz

http://www.jrazzcreations.com


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peter mcauley
Re: Optical Flow in Sony Vegas: How Does It Work?
on Jan 3, 2011 at 8:21:00 pm

Hi Jeremy,

I think you must have an older version of the (BCC) software - download the latest (free) upgrade for BCC 7 from our website (borisfx.com/downloads) and install this and you should be able to use Optical Flow just as you describe with the expected result.

Cheers,

Peter.



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Jeremy Rasnic
Re: Optical Flow in Sony Vegas: How Does It Work?
on Jan 3, 2011 at 8:30:51 pm

Hi Peter. Thanks for the response. I have version BCC704OFX_32Bit_Release and the 64 bit one. Are these not most current?

Also, has the help file been updated (the pdf)?

j razz

http://www.jrazzcreations.com


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peter mcauley
Re: Optical Flow in Sony Vegas: How Does It Work?
on Jan 3, 2011 at 8:34:07 pm

I just tried BCC 704 32 OFX with Sony vegas Pro and it worked fine. Are you using Vegas Pro 10b or 10a? I'm using 10b - maybe that's the difference.

Cheers,

Peter.



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Jeremy Rasnic
Re: Optical Flow in Sony Vegas: How Does It Work?
on Jan 3, 2011 at 11:03:17 pm

Sorry I didn't answer the basics. I know that is forum posting 101.

I am using Sony Vegas Pro 10b (32 and 64). I am runing a dual boot machine with both Vista ultimate 64 and Windows 7 64. I have 8 gigs of ram and two quad core processors running the machine.

I think I have the most up-to-date version, it more than likely is that I don't know how to use the effect properly as the pdf help file is not tailored to Vegas.

Perhaps you could tell me what you are doing to make it work or detail for me how the functionality is to work within Sony Vegas?

Thanks.

j razz

http://www.jrazzcreations.com


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peter mcauley
Re: Optical Flow in Sony Vegas: How Does It Work?
on Jan 4, 2011 at 2:54:15 pm

Hi Jeremy,

So here's how I am using the BCC Optical Flow filter in Sony Vegas Pro 10b:

• Locate the BCC Optical Flow filter in the Video FX directory and drag it onto the clip that you wish to retime
• Set the Velocity parameter to the value that you want the clip to use

Note that you will see black frames at the end of the clip (if you speed it up) where there is no more image data to work with, ie, if you have a 5 second clip and set the velocity to 500 percent then you will have 1 second of video followed by 4 seconds of black frames. If you use the filter to slow down a clip, Optical Flow will generate synthetic inter-frames to produce the slow motion effect.

Velocity values between 0 and 100 will slow down the filtered clip, while values in excess of 100 will speed up the filtered clip.

Cheers,

Peter.



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Jeremy Rasnic
Re: Optical Flow in Sony Vegas: How Does It Work?
on Jan 4, 2011 at 4:41:02 pm

Okay, we are doing the same thing. However, what happens when you split the clip where the black frames start and the "optically flowed" media ends? What happens on my end is that the optical flow fx does the math yet again and shortens the clip by the same amount resulting in an even shorter clip and more black frames.

How do you effectively remove the black frames without having to render out that portion of your timeline? It would seem logical that you could split the clip and it retain the effect without doing the math again unless you change parameters in the OFX window. I have not found this to be true.

So again, what happens once you split your clip with Optical Flow applied? If you get the same results as I do how should one's workflow look when using this effect within Sony Vegas?

Thanks again for staying with me on this.

j razz

http://www.jrazzcreations.com


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peter mcauley
Re: Optical Flow in Sony Vegas: How Does It Work?
on Jan 4, 2011 at 5:12:30 pm

Okay - I understand what you are trying to do.

To trim away the black frames I think you need to create a nesting and then trim or cut back the nested sequence instead of directly cutting the filtered clip. Does that make sense? If so, can you try that to see if it works?

Cheers,

Peter.



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Jeremy Rasnic
Re: Optical Flow in Sony Vegas: How Does It Work?
on Jan 6, 2011 at 2:59:10 am

Hi Peter,

Thanks again for hanging with me on this one. I understand what you are saying about the nested veg file, but surely this was never the intention of the BorisFX team as a method of implementation. I would think this to be more of a work around.

Regardless, I have a question in with one of the guys who works with them and am waiting a response on the intended workflow. It could just be that the limitations of Vegas do not allow for the straight-forward workflow of this particular unit.

j razz

http://www.jrazzcreations.com


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Dirk de Jong
Re: Optical Flow in Sony Vegas: How Does It Work?
on Jan 6, 2011 at 6:54:39 pm

I spent some time looking at it yesterday and agree that it's a bug. We're investigating to see if it's something that can be fixed from the plugin side or not (we hope so). In the meantime the status (as you've seen) is basically that time effects that result in a duration shorter than the original source clip are unexpectedly truncated (with black frames) if the clip is trimmed shorter than it's original duration. The workaround at this point seems to be to apply such an effect to the untrimmed source, then either prerender (render to another track for example) or use it through a nested sequence saved as its own (.veg file) which can be imported into the larger sequence and trimmed to the desired length. We hope to offer a better solution (hopefully to be included in a BCC 7 for Vegas point update)

_________________

Dirk de Jong
BorisFX
dirkd@borisfx.com



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Dirk de Jong
Re: Optical Flow in Sony Vegas: How Does It Work?
on Jan 6, 2011 at 7:30:45 pm

It occurred to me that another workaround in some cases might be to do such time effects on a lower video track applied to the full duration source clip and positioning successive shots on the track above such that they obscure the black frames that occur as a result of speeding up the original source clip. Obviously there would be cases where this might not be a feasible workaround at all, but in some cases it actually might be preferable to the other 2 possible workarounds mentioned in the previous post. Again, we are investigating and hope to be able to offer a better solution in an update of possible



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Jeremy Rasnic
Re: Optical Flow in Sony Vegas: How Does It Work?
on Jan 7, 2011 at 2:56:29 am

Thanks Dirk. I look forward to a better workflow using this tool as I think it will prove to be invaluable for footage that needs to be slowed down or sped up.

As for your second post on this thread, that would work okay as long as audio was not attached to the clip. If it is, you would have to do the math to get it to sync up correctly if CTRL+Drag's range was exceeded.

j razz

http://www.jrazzcreations.com


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