As you're editing dialog, effects, ambiences, and even music cues in Pro Tools, you'll probably find a need for time stretching, where you want to shorten their length in a region without altering its pitch, or actual pitch shifting where you do want to raise or lower the pitch of a sound without stretching the region in time. X-Form is an AudioSuite plug-in for high quality time compression/expansion and formant correct pitch-shifting. It's part of complete production toolkit too. In this movie we'll explore some effective uses of the plug-in. So here in our Timeline we have an ambience track that might be a bit too short.
We have the track soloed and let's hear what it sounds like. (White noise) So it's the background sound of a race, but you can see it doesn't extend far enough into the scene. It ends here. Now normally we would try to take the Trimmer tool, F6, and pull it out, but as you can see that's the end of the region. That's all we have recorded. So we're going to have to use time compression/expansion to lengthen the size of this clip and we don't want to pitch shift it as we do that. So let's go up into the X-Form plug- in. AudioSuite > Pitch Shift > X-Form.
So here's the X-Form plug-in. Audio Type is the type of content you wish to process. There's a couple of settings in here. We have Polyphonic, Monophonic, and Polyphonic with a Faster setting. Polyphonic uses a different algorithm for more harmonically complex sounds. Pro Tools gives the example of a multipart musical section. Monophonic is for-- in Pro Tools words-- it's monophonic sound such as a vocal melody. And Polyphonic (Faster) is a simplified polyphonic algorithm that takes less time and a trade-off of lower quality.
Since the sound we're working on is neither, let's start with Polyphonic and we're just going to have to do a trial- and-error and see if it sounds good this way or with Monophonic. Below this section, we have our Time. So this is the way we can assess how much longer or shorter we're going to affect this particular region. We can change the Unit here to Time Code, which would make sense since we're working in video. And let's make a selection across the track to see how long we need this section to be. So we wanted to go to about here, a little bit over that section so we can crossfade it out.
And if I look up in my main counters here, I can see the length is a little over 13 seconds. So with that information, we need to actually select the region I'm going to affect, so select that region, then go in here, and I'm going to type in 14, and go into the next field and I'll type 00. So here we go. 14 seconds. It'll expand this region from its original length of 10 seconds to a total length of 14 seconds. Let's preview it for audio quality. (White noise) Okay, that sounds pretty good.
Let's actually check out what that would sound like for the Monophonic setting. (White noise) Okay, that sounds worse to my ears, but notice that in the Monophonic setting, we have a Window setting that's active, so we can actually increase this window. Window is a fine-tuning control basically. Smaller window sizes will be good for drums and percussion and larger window sizes will be good for longer sounds like we have here. So let's increase the Window and see if it helps it all. (White noise) It helps a little bit, but I'm going to go back to the Polyphonic setting and listen to how that works.
So when we're in the Polyphonic setting, Transient Sensitivity is active and the Window is grayed out. So in this case, Transient can be adjusted. You want a lower Sensitivity setting when you're working with rhythmic material and maybe a slightly higher setting when you're working with less rhythmic material. I'm going to bring up the Sensitivity a little bit here. Again, it's kind of a trial-and-error thing. I'm going to preview it and see how it sounds. (White noise) Okay, so out of all the settings I'm going to go with that one.
We still have our time set in there, so we'll hit Process and the region will be lengthened. Okay. So as you can see, our region got lengthened and its appropriate length now. Take a listen to it. (White noise) That's it by itself, but let's put it in the context of the session and we can hear what it sounds like. (Vietnamese dialogue) So that sounds pretty good as a background race and we'll probably want to do just a quick crossfade out as we get out of that scene.
So the next thing we're going to do with X-Form is not a time
compression/expansion, but rather a pitch shift. So it's kind of the inverse
of what we're doing.
I'm going to click on
So here we're able to take this knob and lower it down and then we have Semitone, which is a musical increment, but we also have Percentage. So if I take it down say little over 3 semitones, that means that we are 80% lower in pitch than the original sound. X-Form also does allow for something formant pitch shifting, and this feature is to be used when you're pitching a voice or some other instrument that you want it to sound as natural as possible. Basically, it takes into account the harmonic series, which makes it more natural sounding. But in this case, the whoosh sound isn't as complex as a voice, so we're going to leave Formant off.
I've had some bugs when I hit Preview in the Pitch Shift area, so I'm going to stay away from that for now. We're going to process it and if we don't like it, we can undo it and redo it later. So here we're going to go process and pitch shift it out and let's take a listen. (Whoosh) So I've here the original and the newly pitch shifted one. (Whoosh) As you heard, the first one was a little higher pitched, the second one was a little lower in pitch, and that gives just enough variation, just what I wanted. So one more thing you can do with the X-Form plug-in is you can set it as your default time compression/expansion tool.
So if I go up to Pro Tools > Preferences, here under Processing we have the TC/E Plug-in. Now here we can go in and Digidesign X- Form will show up as the tool we want to use as opposed to just the regular Digidesign Time Compression/Expansion, and since X-Form is a higher-quality plug-in, I would like to set it up as our default TC/E plug-in. And what this means for us is back in Pro Tools, when I take the Trimmer tool in the TC/E mode where it actually allows you to trim out a region and lengthen or shorten it, Pro Tools will be using the algorithm from X-Form to do that processing.
So the X-Form plug-in is a real valuable tool in your bag of tricks. If you use it correctly, it can allow you for some effective and seamless audio stretching or some dramatic pitch shifting, and it'll give you a lot of options and flexibility in your audio for video project.
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