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How to Convert Frame Rates

We're going to show you how to successfully convert from one frame rate to another using footage interpretation and pitch shifting.

Video Transcript

Well, you're about ready to edit and you realize that you have footage shot at different frame rates in the mix. Now what? Well don't panic; we're going to show you how to successfully convert from one frame rate to another using footage interpretation and pitch shifting. And just like a sharp new outfit, all your footage will match and come together, to help your project look its very best.

Video is nothing more than a series of still images played back in succession, giving the appearance of motion. Each of these images is called a frame and the rate at which they are played is referred to as the frame rate. In a perfect world all footage would be the same rate and we wouldn't need to know about such things, but then, we know better right? In reality, we might find ourselves with footage from a multi-camera shoot where the cameras were inadvertently left to capture at different frame rates. Or, we may have just gotten a foreign distribution deal for our independent film and need to convert it to the European PAL standard of 25 frames per second. Let's see how this works.

Begin by opening your editing software. We'll be showing you the process using Adobe's Premiere Pro CS5 but most common editing programs should have similar functions. Import the files whose frame rates you wish to change. This first piece of footage is a video-only clip with no audio attached. Double-click to open it in the "Source window" and play it to get a sense of its motion. Notice its properties that appear to the right of the preview window. Among other things this tells us that its frame rate is 23.976 frames per second. This was shot on a 24P DSLR camera and will be part of a television commercial, therefore it needs to be converted to the NTSC broadcast standard of 29.97 frames per second. Right-click on the clip in the Project window, go to Modify and click Interpret Footage. The Interpret Footage dialogue window appears. The first section, entitled Frame Rate, will allow us to either keep the existing rate or change it. In the text box at the right of Assume this frame rate enter 29.97. While the "Pixel Aspect Ratio" and "Field Order" can be adjusted we want them to pull this data from the file itself and so we'll keep their default settings. Click "OK" and notice again the clip's properties to the right of the preview window. We see now that the frame rate has changed to 29.97. As a result in this side-by-side comparison we can see that the higher frame rate looks a bit smoother than the lower one.

Now all this works fine if you're working with video footage that has no audio component. But what happens when you're working with linked audio? This is our completed television commercial at its original frame rate of 23.976 . As before, change the clip's frame rate to 29.97 then place it in the timeline. Let's listen again. While the audio portion remains synchronized with the video, it's pitch has become significantly distorted. To correct this, go to the "Effects window" and open the "Audio Effects" folder. Since ours is a stereo file, we'll open the "Stereo" folder. Scroll down and find the "PitchShifter" effect. Click and drag it onto the clip's audio track. Now with the clip selected, open the Effect Controls window. Go down to the "PitchShifter" effect and twirl it open to reveal its properties. "Bypass" allows you to toggle the effect on and off while previewing in order to monitor your progress. Opening "Custom Setup" reveals a pair of dials for adjusting "Pitch and Fine Tuning" and a checkbox labeled "Formant Preserve." Twirling open "Individual Parameters" allows you to make the same adjustments using sliders. We'll be using the "Custom Setup." To adjust the pitch of your audio track, go down to the bottom of the "Effect Controls" window and click the "Toggle looping audio playback" button. It looks like an arrow folded back on itself. Click the "Play only the audio for this clip" button next to it. This will loop the audio while making adjustments, allowing you to hear the changes you are making. This is a CPU intensive process and depending on your system you may experience the audio dropping out as you adjust the parameters. If this happens click the "Play only the audio for this clip" button to stop looping, pause a moment then try it again. Shifting the "Pitch" dial to the left will lower the pitch. Get it close, then use the "Fine Tune" dial to get it just right. The "Formant Preserve" checkbox is intended to prevent the all-too-common "Mickey Mouse voice." Click it on and off to see if it helps. There you have it. Your frame rates are all matched up for distribution and your audio is synchronized and properly pitched to people pleasing perfection. Here's the before and after comparison.

Frame rates that match each other, as well as their distribution requirements, will keep both your audience and your clients happy. And using the techniques we've shown you, you'll be able to deliver your future projects that look and sound their very best.

Comments

reyve's picture

I'm using Magix Video Pro 17. I know it's consumer. I have been mixing footage that are 29.97 and 23.97 into one file and when I select the output, whether it was 29.97 or 23.97, it seems smooth both ways. Does the rendering automatically Interpret Footage? Or is my just untrained? Also, in this video, since the original was 23.97, why is that less smooth than the 29.97 version?
burchdc's picture

Your Magix Video Pro is probably adding a 3:2 pulldown to the 23.976 footage, which is why it looks smooth. Every time you see a movie on broadcast TV (except for newer, 1080p cable and satellite services), this is what you are seeing. Essentially, a field is duplicated at regular intervals, creating frames at appear to be interlaced (every other frame, to be exact). When viewed on an interlaced monitor, frames that have temporal difference between fields look smooth because of the way the monitor displays the image. On a progressive monitor like an LCD, this shows up as motion blur, which in turn creates the illusion of smoother motion. Native 24p footage should not have looked as jumpy as what was shown on the video. I believe what we are seeing there is an artifact of the difference between the frame rates of the source video and the actual video being played back on this web site. That is, the video we are watching is probably 30p, and the 24p source was improperly converted before being shown in the split screen. This will cause the video to appear "jumpy", because the frames don't line up. If you were to watch the 24p source on your own monitor, it would look just fine. Again, this is the frame rate that movies are shot in.
remofiore's picture

Hi great tutorial, something most of us newcomers don't know about is frame rates. Although I already knew about this. there is one thing however, Is there some kind of chart that I can refer to for frame rate standards ? Some kind of reference that guides me through the general standards for etc. I'd like to know more about this technical aspect. Thanx for you help Rem (^_^)
burchdc's picture

Remo, I'm not sure if they're actual standards, but here are the most common frame rates (at least for NTSC): 23.976 progressive (what most people call '24p') 29.97 interlaced 30 progressive 59.98 progressive (also known as 60p) PAL video runs at 25 fps interlaced; I'm afraid I don't know anything about their progressive standards. I would assume they also use 60p and 24p (although I believe the resolutions are different in PAL, at least for standard definition). There is such thing as actual 24 fps video as well, but this is rarely used, unless your destination is film out. Most professional and "prosumer" HD cameras today will shoot in either 720p, 1080i, or 1080p. Usually, the 720p resolution allows for 24p, 30p, and 60p frame rates. 1080i runs at 29.97 interlaced (the same as standard definition NTSC) or 25 fps (in PAL), and 1080p usually allows for either 24p or 30p. Hope that helps.
remofiore's picture

Hi David thanks for the advice, it's helped me tremendously. I live and work in Italy so obviously I woprk in Pal but it pretty much works the same way thanks agian and I'm so sorry it took me so long to reply. However have subscribed to hard copy of the mag no doubt there will be plenty more there to help me. Have a good day Na dgood work ! Rem
burchdc's picture

I'm sorry, but this is horrible advice. First of all, using this technique will speed your video up (which may not be a bad thing if that's the effect you're going for, but is catastrophic if timing is critical). Second, I would ONLY use a pitch-shifting tool as a last resort. These kinds of tools introduce all sorts of audio problems, especially when using music. Instead, in the case presented in the video, a much better approach would be to use a 3:2 pulldown. This essentially duplicates a field every 3rd field in the sequence, so that 24p video plays back at 30 fps. Incidentally, this is what DVD players do when playing back a 24p movie on an interlaced TV, and is the same technique that has been used for decades to translate film to video (before the advent of digital video that is capable of playing at a native frame rate of 24 fps). A much tricker conversion would be to go from 29.97 fps to 24p. In my experience, the best way to do this (and avoid unnecessary flicker) is to first convert the footage to 60p. This will de-interlace the footage and provide more frames to work with when converting to 24 fps. I've found that Adobe After Effects does a pretty good job at this. Once you have your footage in 60p, most NLE software today will allow you to place it in a 24 fps timeline and do the rest of the conversion for you. Of course, most NLE software today will allow you to do this with 29.97 fps interlaced footage as well, but I have yet to see one that does this well. If your software won't allow mixed frame rates, then you can convert your 60 fps footage to 24p using software like Compressor or Adobe Media Encoder. In either case, I wouldn't touch the audio with pitch-shifting tools. I only use a conform function if I purposely want to speed up or slow down my footage (such as conforming 60p to 24 for a nice, smooth 'over crank' effect).
radsonpro's picture

this is new to me and I love this technic. As for me i normaly have to export the the clip to a movie file and change the frame rate and then inport it to my project. Any way there are many ways to go to heaven.
reyve's picture

Question on Burning DVD and Blu-ray's: What are the frame rates of DVD and Bluray's? Are they both 24p/23.97 all the time? Or can they be burned at 30fps/29.97?
Barry's picture

While I find Videomaker videos very helpful. The title of this is very misleading. HOW TO CONVERT FRAME RATES. That's not what this is. It's HOW TO CONVERT 23.976 TO 29.97! Or HOW TO CONVERT ONE LOWER FRAME RATE TO A HIGHER ONE. I think most people want to know how to convert it the other way around. If that is possible. Please title your videos more carefully
guyroth's picture

Great toturial. It shows how to convert clips in Adobe CS. The question is how to do similar action in PowerDirector. I'd like to edit a movie with clips from 2 different sources. One has 25FPS and the second has  30FPS. So I'd like to convert one of them to the second so both of them will fit the project's Frame rate settings. otherwise it looks bad in the output produced video. 

Does anyone know how to do it? Is it possible at all in Cyberlink PowerDirector. Or this is an advantage of Adobe Premier only?