Set your frame rate either for either the fastest of your source files, or the one you use the most of, or match whatever output frame rate you want. Personally i prefer the last choice, though the second choice has a lot of merit.

Vegas will work as best as it can and will certainly make some output from each input file. How it does so may or may not give wonderful results, but it will give a viewable result. As musicvid10 mentions, you can either duplicate/drop frames, or interpolate. Interpolate (resample) works by blending adjacent frames together. Since this results in output frames being created from two input frames most of the time you can see fuzzy, doubled images. This is the price of trying to maintain smooth movement.

The other option is to disable interpolation (resampling). Vegas then simply uses the one frame from the input file closest to the time of the current output frame. If the source frame rate is slower than the output then Vegas will end up repeating the frame as many times as necessary to fill the longer output frame. If the source frame rate is faster then Vegas will have to skip over some source frames, dropping them from the output. The result is clear and sharp without the doubling, but the movement can be jerky. You should try both ways and see which you find less objectionable.

Resampling is controlled in each individual clip (actually event) on the timeline one at a time. Right-mouse-button click on the clip on the timeline and from the popup menu that appears choose disable resample to turn off interpolation, or smart or force resample to turn it on. Sadly there's no global setting, so experiment on a short project with just a clip or two from each frame rate to see what it's going to look like before you do a long project.

I’m doing a music video and received a video from a singer who used 1080p @ 50fps. I need to record the video for his duet partner and where they're singing together I need to do a split screen. I haven't bought a camcorder yet to do this project and really don't' want to spend more than $100.

Since I haven't done the 2nd video yet I can choose a camcorder and a format that will be the most compatible. I assume a 50fps camera will be too expensive. I've noticed that several cameras I'm interested in can do 1080 @ 15 fps or 720 @30fps. I'm not seeing 25fps, which I would think would work better with the 50fps. If a camcorder can do 30fps, will it also be able to do 25fps? Or will it list 25fps in it’s specs if it’s able to do that?

Considering this situation should I record at 720 @ 30fps instead of 15fps at 1080? I’m not sure whether 1080 for a YouTube video will be any better than 720. It’s seems to me that avoiding jerkiness and fuzzy images would be far more important than whether it’s HD or even SD. What do you think?

I suppose another option is to convert the 1080 @ 50 fps to a more compatible format. Are there any free or 30 day trial programs that will do a conversion? I’m concerned about the split screen with his video and my video with different formats. Please give me some advice on this and thanks for all the help so far.

Under $100 is REALLY limiting your choices a lot. You're not going to get much better than a "webcam" quality machine for that price, so good luck! That part considered, you're going to be introducing probably substandard quality video on your end so i wouldn't worry too much about any other limitations.

25/50fps is common in Europe, which used the PAL 25fps system instead of the 29.97/30fps NTSC used here in North America. Definitely record at 30 (actually 29.97). You would notice and be bothered by the lack of frame rate far more than the lower resolution. It's also a closer match to the 50 from the other camera.

You can use Vegas to convert the 50fps video, but don't bother doing it as a separate step. Just put that video and yours on separate tracks, one above and one below the other. I'd probably pick 29.97 for the project and output frame rate. Set up the split screen as you wish, and then on the 50fps video experiment with turning resampling on or off to see which way you like it better. Vegas will do the necessary conversions on the fly.

Thanks for your suggestions. It sounds like good advice. I have an audio recording studio and the Artist is from overseas, which explains the 50fps. He got a video student to do the video and it’s just a video of him playing guitar and singing his song and it doesn’t look that good. Which is not a reflection of the quality of the camera, but the lighting and real basic approach.

So it’s not like I’m trying to compete with some movie studio with wonderful quality. This will be a YouTUbe sort of video and 99% will view it only on their computer, so it seems to me HD is pretty much overkill and likely to not really make a difference. Do I choose the output to be 720 and 30fps?

Is there a conversion when mixing the 1080 and 720 resolutions? Do I need to set the output for either 720 or 1080? Or are those resolutions ok to coexist in Vegas? Please let me know if any of my assumptions seem off base to you or not reasonable for this sort of project.

There are many camcorders in my price range that can handle 720 @ 30fps, but not 1080 @ 30fps. It seems the ones that use 1080 want to use the 15 fps. If I choose 30fps as the output, won’t that mean that my video 720 @ 30fps will not be altered? Only the 50fps video will be altered.

It seems to me that it would be better for Vegas to drop some frames to match the 30fps, instead of resampling. 50fps seems overkill to me and as long as Vegas can drop frames in a smart way, shouldn't that work fine? So if I turn off resampling, will that mean Vegas will drop frames to solve the conversion problem? If I get Vegas to convert the 50fps video to 30fps, would that make the computer work better as far as viewing the video, since it wouldn't’ have to work so hard converting on the fly?

Keep in mind neither my video or the 50fps video have any fast movements, just people lip syncing the song, so wouldn't that mean I’d likely not have problems with a jerky video? I definitely don’t’ want jerky or fuzzy videos. I think the lower resolution won’t be a problem.
I apologies I’m such a newbie on this video stuff and I really appreciate excellent advice I’ve already gotten.

Vegas resizes video frames to match the output size automatically. You probably don't need to worry about any of the details unless you're also converting interlaced to progressive.

There's no need to convert the 50fps 1080 to 30fps 720 before putting it in your project. Vegas will do it on the fly while you are editing and rendering. In fact, it's preferable not to, since converting it first will end up in it being processed twice, once for the conversion and once for the final render. Using the original video will result in it being processed only once. As far as extra effort involved in doing the conversion on the fly, any computer produced in the last few years should be able to handle it just fine. Your preview frame rate MAY drop a little while you are previewing, but probably not enough to interfere with the editing process. Vegas will be doing more work to put the two separate videos together side by side in the frame than doing the conversion. If you absolutely need full frame rate playback while editing to check that an edit is exactly right you can highlight a few seconds' worth around the edit point and press shift-B to do a RAM prerender, which will then play that section back at full frame rate.

I agree with dropping frames to get from 50 to 30. The motion won't be completely smooth, but i doubt anyone would notice the difference over native 30 unless they knew to look for it and were utterly bored by the music in the video.