Variable Frame Rate vs 29.97 Fixed vs 30 Fixed

stevefoobar2 wrote on 12/22/2024, 5:46 PM

Hello everyone. I've been editing videos and using Vegas for many years as an amateur/hobbyist since the days of 640 x 480 video. One question that I never got a satisfactory answer about or fully understood is frame rate, especially how it relates to video editing and rendering.

These days, 98% of my videos are shot on a smartphone with the stock Android camera where I have no control over the frame rate. I always specify "30" or "60" fps in the camera app but of course, it does what it wants to in terms of a variable frame rate that is just "close" to the frame rate I asked for. I always play these videos back on computers or upload them where people play them back on computers. They are never broadcast anywhere. I never write to media like DVD or Blu-ray discs, etc.

When I import them into Vegas and accept the "Set the project to the video..." message, it always sets the frame rate at some odd value like 30.046 for example, if I chose "30" in the phone camera app.

  1. Does anyone know where this value comes from? Is it the average frame rate the camera shot with?
  2. Given my explanation of the way I use these videos, are there advantages or disadvantages to forcing the Project Properties Frame Rate to a fixed 30 fps or 29.97 fps?
  3. These days, with everything digital as I explained in my use, is there even a reason to use 29.97 fps anymore over 30 fps? Are there pros and cons between these two frame rates?
  4. If I have the Project Properties frame rate set to one thing (e.g. 30.046) but then render to 30 fps, is that OK or does it cause potential problems?

Thanks a lot.

Comments

EricLNZ wrote on 12/22/2024, 5:55 PM

Good questions which probably affect many these days.

Q1 - I suspect it's the average possibly obtained by dividing the total time by the total recorded frames

As for the other questions I'd use 30 fps for your project if that is what you set your camera to record to.

 

DMT3 wrote on 12/22/2024, 10:22 PM

Most low cost or phone cameras do not have an aperture to control the light coming in. Cameras will vary the frame rate to compensate. You can test this by shooting low light and see if the frame rate is slower than a bright day shot. 30fps should work most of the time. 29.97 is still a viable frame rate but is based on the old standard of 60hz electricity. In normal 29.97 interlaced TV, originally in B&W there were 30fps divided into 60 fields. (half frames basically). When color was introduced the frame rate had to be slowed down to allow for the color information, thus 29.97. These aren't issues anymore, but I believe the FCC still requires that broadcast TV be compatible with old and new TVs.