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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.