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Modifying Clips

Sooner or later, footage will be captured incorrectly, imported wrong, or just plain need modification. There will be lots of times when you’ll need to break the rules (such as when dealing with overcranked footage). This section explains exactly how to make important changes to how your footage plays back and is used.

Adjusting Audio Channels

As you learned in Chapter 3, “Setting Up a Project,” Adobe Premiere Pro has four track types: Standard, Mono, 5.1 and Adaptive. A standard track is a single track where you’d put a mono clip (like narration) or a stereo clip (like music).

You may be familiar with other editorial tools that use a pair of tracks to handle stereo (usually a pair of mono tracks). A cool feature of Adobe Premiere Pro is that you’re able to handle the audio easier because it’s a single element. Prior to CS6, it was crucial to understand how to modify audio channels in a clip, but it’s a skill that is nearly no longer necessary.

Switching incorrectly set stereo elements

If an imported stereo clip was incorrectly interpreted as a pair of mono tracks, it’s possible to fix it pretty quickly.

In the 04_getting_started project, we intentionally imported the Mono music.mp3 clip by forcing it to be a pair of mono clips in the Audio preferences by setting the Default audio tracks (on import) to be Mono. If this clip was dragged to a Timeline, it’d take up two tracks.

To fix it, all you have to do is choose Clip > Modify > Audio Channels and choose the Stereo preset (Figure 4.18). If you then drag the clip to a Timeline, it will take up only one track.

Figure 4.18

Figure 4.18. Choose Clip > Modify > Audio Channels to change the audio information. Just remember that if the audio clip is already used in a Timeline, that version of it won’t be changed.

Forcing an audio track override

When you import audio, Adobe Premiere Pro uses the default interpretation based on the clip. This happens based on the Audio preferences. You can resolve 99 percent of improper audio imports by setting the Adobe Premiere Pro Preferences correctly.

  1. Choose Premiere Pro > Preferences > Audio (Mac) or Edit > Preferences > Audio (Windows).
  2. The default is Use File. If desired, adjust the setting to your needs.

    In situations in which you’re bringing in audio with multiple mono tracks, such as an interview where each person has a microphone, it might be warranted to override a stereo recording to be interpreted as a pair of mono tracks.

Interpreting Footage

There are some very good reasons for reinterpreting your footage. They include graphic files or footage that is missing a flag for pixel aspect ratio correction or correctly removing extra frames from 24p material.

Of course, any time you monkey with the way Adobe Premiere Pro interprets the footage, you’re taking the chance that your footage might not look right. Choose the wrong setting and your alpha channel may be reversed or a video file won’t play back because of an incorrect frame rate.

But sometimes you’ll have to tweak these settings, if, for whatever reason, they were interpreted incorrectly.

For this section, you’ll be looking at the footage in Lessons and Media > Lesson 04 > 04_getting_started.

Assigning a frame rate

The footage frame rate is set in the camera, but the sequence frame rate is set by you when you create it. You can of course cut footage of differing frame rates together into the same sequence, and Adobe Premiere Pro will automatically blend the frames so the proper speed is maintained.

But what if that’s not what you want? Perhaps you shot footage at 60 frames per second to conform it to play back at 30 frames per second. This technique works only with cameras that have a high frame rate (like 720p60 cameras). Otherwise, your best bet is to choose Clip > Speed/Duration to change the speed of the clip, which is mentioned in Chapter 7. With this technique, you’ll get a nice, slow-motion effect.

Let’s slow down a clip that has been shot at 60 frames per second.

  1. Open Sequence 01 Frame Rate.
  2. Play back the footage and observe the speed of the woman walking through the frame (Clip 0097SJ_60.mp4).
  3. In the Clips to be Adjusted bin, select 0097SJ_60.mp4, and choose Clip > Modify > Interpret Footage (Figure 4.19).
    Figure 4.19

    Figure 4.19. It’s possible to reinterpet the frame rate, pixel aspect ratio, field order, and alpha channel.

  4. Select the “Assume this frame rate” option, enter 29.97 frames per second, and click OK.
  5. Drag the right edge of the clip to extend the shot.
  6. Play back the sequence and watch it to see the impact of the frame rate change.

Interpreting pixel aspect ratio

There are headaches and then there are Headaches. When your files have the wrong pixel aspect ratio, they will look distorted. Computers have square pixels; the height and width are the same. Video pixels are often non-square; that is to say, they have a different width than height. Being able to interpret non-square pixels correctly is a technical necessity because so many cameras can shoot multiple sizes and frame rates (while preserving affordable recording options).

You’ll see non-square pixel aspect ratios most often in standard-definition files. Both wide-screen (16x9) and “normal” (4x3) video files have the same number of pixels. It’s the shape of the pixels that makes the difference. The 16x9 pixels are wider (and hence fill out the television frame).

The pixel aspect ratio information is stored in the raw media file. When interpreted incorrectly, it looks like Figure 4.20.

Figure 4.20

Figure 4.20. Both clips are the same video. The pixel aspect ratio of the one in the Source Monitor (left) is incorrectly interpreted, whereas the shot in the Program Monitor (right) is correct.

Let’s fix a clip that’s incorrectly flagged as square pixels.

  1. Open the sequence 02 Bad PAR. The sequence contains two clips. The red clip is being interpreted incorrectly as being D1/DV NTSC (0.9091).
  2. Play the sequence and compare the frame sizes.
  3. Right-click the Red clip, and choose Reveal in Project.
  4. Choose Clip > Modify > Interpret Footage. Click the Pixel Aspect Ratio Conform To button, and choose the D1/DV NTSC Widescreen 16:9 (1.2121) option.
  5. Click OK. The footage conforms to the correct pixel aspect ratio and fills the frame.
  6. Watch your sequence to see the impact of the change.

Field order

Video can be recorded in fields, usually 1/60 or 1/50 of a second apart. They’re stored together as a single frame. The term for this is interlacing. Although interlacing is a depreciating technology, you’ll still encounter it.

Should Adobe Premiere Pro store the field order (and retrieve it) as the first field, the top field? Or should the field order be retrieved by the second field (lower field) first? Some cameras shoot progressive where both fields are shot at the same time and stored together to make up a frame.

Generally, unless you’re shooting progressive, high definition is generally upper field first. Video is generally lower field for standard definition. If you see “tearing” or “sawtooths” when you play back the video, that may be a sign of a field problem. It’s easiest to see when the video is output on a broadcast monitor and jitters oddly during playback.

If you need to fix a clip that’s incorrectly flagged with the wrong field order, follow these steps:

  1. Select the clip
  2. Choose Clip > Modify > Interpret Footage.
  3. Select the Field Order Conform radio button and choose the appropriate field choice (Figure 4.21)
Figure 4.21

Figure 4.21. There are three different options for field choices: Progressive, Upper Field First, and Lower Field First.

Alpha channels

Alpha channels determine the visibility of parts of a clip. However, transparency can be confusing because of how the term alpha channel is used. The term alpha channel is used when it’s on a clip, but when you view only the alpha channel, it’s typically called a matte.

Two alpha channel settings are available in Adobe Premiere Pro.

  • Ignore. This option disables the alpha channel (meaning no transparency).
  • Invert. This option can be used if the transparency is reversed; you’ll see the background, not the foreground (Figure 4.22).
Figure 4.22

Figure 4.22. When the alpha channel is reversed, as in this example (a figure is animated on a gold matte background), you see the background, not the element.

Let’s fix a clip that has its alpha channel incorrectly inverted.

  1. Open the Sequence 04 Bad Alpha. Go to frame 25;11.

    The sequence contains two clips. The top clip is being interpreted incorrectly over a gold matte.

  2. Right-click the top clip (Bad Alpha), and choose Reveal in Project.
  3. Choose Clip > Modify > Interpret Footage. Select the Alpha Channel option, and deselect the Invert Alpha Channel option.
  4. Click OK. The footage shows the correct areas of transparency.
  5. Watch your sequence to see the impact of the change.

Modifying Timecode

Modifying the timecode means the clip will no longer line up with the original media it was sourced from, making it nearly impossible to retransfer or recapture. So, be careful when you do this.

However, you might want to modify timecode for a couple of reasons: to sync by time-code or to assign timecode to a clip like a DSLR clip or an audio track meant to be used in multicamera editing.

To modify the timecode, follow these steps:

  1. Select any clip in the Project panel.
  2. Choose Clip > Modify > Timecode.
  3. Enter the new timecode, and then select Set at Beginning or Set at Current Frame (Figure 4.23).
    Figure 4.23

    Figure 4.23. The Timecode adjustment window. Be aware that when you modify the timecode, you may be causing a mismatch if you ever need to relink to the nonmodified original source.

  4. Click OK to make your adjustment.
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