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Old 15th March 2013, 12:30   #1  |  Link
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Matching two videos with different FPS

Hi, I screen captured my laptop screen in Camstudio at 60 FPS, any lower than this and it looked too jerky. I recorded myself on my PAL DV camcorder which records at 50i. I recorded myself DJing and used the softwares internal audio recorder so I also have a seperate audio file. I want to sync the videos and audio together and upload to YouTube which will have to be 25 or 30FPS.

CamStudio's codec doesn't seem to be compatible with Sony Vegas, so i'll use VirtulDub to create a Lagarith lossless file.

I don't know at what stage I should change the FPS and to what number.

Do I change the screen capture video from 60 FPS to 50, 30 or even 25 before I put it in Sony Vegas?

Do I change the DV video to 60i, 50P or deinterlace to 30 or 25 FPS before I put it in Vegas?

Do I Render The Sony Vegas Project to 50/60 FPS and let Youtube half it or half it myself and render to 25/30FPS?

I also don't know what script to use to change the FPS in Avisynth?


Last edited by Jonaldinho; 15th March 2013 at 12:53.
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Old 15th March 2013, 13:45   #2  |  Link
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I believe anything Youtube gets its hands on gets re-encoded to 30fps, so its best to render your final file at that target. This really sucks for recorded PC footage, but there is no way around it since Youtube doesn't want to keep up with advances (seriously, 1080p and 3D but you can't give us 60fps even at 720p, or even color spaces higher than 4:2:0 ?)

For any real life footage, you can probably get away with a using a very good motion blur filter in Vegas, but for the PC capture footage, you are really going to be hard pressed to find a good way to downsample the frame rate while keeping the fluidity of motion you get with 60fps. You could try adding some motion blur to the PC footage, but it will probably be very finnicky and may not come out good even with the best looking setting you can find.

I've tried to figure out a way around the problem myself, but don't really know of one.. The only idea I've ever come up with, but wouldn't know where to start is: Try using a slow-motion / time warp effect on your footage, to slow it way the hell down.. This should leave you with lots of frames (interpolated but, meh) which you could use to change the FPS so it plays back at a faster speed. That -might- give you fluidity of motion but would cost you huge in file size and bitrate. Assuming you could find a way to slow it down, then speed it back up so it plays "normal" at 30 fps in the first place.
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Old 15th March 2013, 13:50   #3  |  Link
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OK thanks, I was just watching a video on how you apply Motion Blur, do I apply Motion Blur on the original 60 FPS footage then render to 30 FPS or do I convert to 30 FPS first and then apply Motion Blur?
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Old 17th March 2013, 02:19   #4  |  Link
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That's a good question.. I honestly have no idea.

Try doing both on a small sample range of frames to see which looks best?
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Old 20th March 2013, 08:32   #5  |  Link
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Unless things have changed recently, YouTube will honour the original FPS up to 30 fps, but anything beyond that will get converted. So 25 fps is also an option, if it is useful in your case. If you have roughly 50% of video and 50% of screen capture, it depends on which you can convert more pleasingly to the other format. My instinct would say to go with 30fps for the screen captured footage and convert the 50i video to 30fps to go with it. If you provide samples, people can give their opinion.
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Old 20th March 2013, 10:51   #6  |  Link
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I think you need 30fps project in Vegas and render it to 30fps in progressive scan. Quality is going to be good for upload in mainconcept avc with modified Internet HD 1080p preset. I prefer 20M bitrate with max bitrate of 28M and 30,000 fps (same as project).
General rule for fps - do not change fps in Vegas unless you know what you are doing. In case you need to change computer footage inside Vegas fps, use "disable resample" option in videoevent settings. This way you'll have perfect stills and on true 30/60 fps you'll mostly never notice the difference. The other way (smart/forced resample) produces blending here and there and at least you'll text doubled=>unreadable.
For the sake of slow/fast motion import 60fps footage into Vegas. It will give the possibility to choose better aligned frame in situation of 150% speed, for example. If it will look jerky to you, change fps outside of Vegas.

As for DV, Vegas works with 50i mostly without problems. At first I'd suggest to import such files directly into Vegas, just don't forget to set up deinterlace method in project settings.

One more thing. Don't forget to tune video levels according to your rendering options.
For Mainconcept AVC you need studio RGB (RGB values in 16-235 range). It might be applicable to CG and might be applicable to DV. Use histogram (Ctrl+Alt+2) to check what you have and apply color correction filters or Levels filter as necessary.
For avi uncompressed or wmv you need computer RGB levels. Computer footage might be in this range already, but DV might need correction.

Also, when you encode into Lagarith (prior to Vegas), stick to RGB mode to avoid complications with RGB<->YUV conversion on both encoder and decoder sides. Vegas naturally works in BGRA and in 8-bit projects imports avi RGB without color conversions.
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avisynth, match fps, multi camera, screen capture, sync

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