Using Quicktime Video
With Audio Workstations
Keeping Everything, Including the Kitchen, in Sync.
In previous articles, we spoke in depth about using the Aurora Fuse card for video playback. Recently, music editor Michael Jay e-mailed me with an important concern for those of you who use that card with Pro Tools.
As he pointed out, when Pro Tools plays back QuickTime video through the Fuse card, the video plays back at the Macs internal clock rate, not at the rate that the Pro Tools system is locked to. The result is a slight drift between the video and the Pro Tools session. Every time you play, youll start out in perfect sync, but as time goes on, the drift will increase. After about 10 minutes, you could be out as much as two to four frames.
Fortunately, if you stop and press play again, youll be back in sync. As a result, this is really only a problem when you are doing long continuous playbacks without stopping. When editing, however, youre generally scrubbing, stopping and playing back short sections. In such cases, the drift is not a concern.
For longer playbacks, though, there are workarounds to the drift issue. One is to use the composite video out of the Fuse card itself as the video sync source fed to your MIDI Time Piece AV, Video Slave Driver or Universal Slave Driver, which are used to lock Pro Tools to house video sync. If you do, Pro Tools will run at the same rate as the Fuse and the Mac, and you will be able to do continuous playbacks with the Fuse card without drift.
Another way to eliminate the drift issue is to move up from a Fuse card to the Aurora Igniter card. These are a bit more expensive, but they can be genlocked to an external reference. If you genlock your Igniter and Pro Tools to the same external reference, you will have no drift.
Dont Let Drift Issues Weigh You Down Get Lite!
To facilitate this, Aurora just introduced the Igniter LT, also known as Igniter Lite. Its a stripped-down economy version of their popular Igniter line of capture cards. While more expensive than the $500 Fuse card $999 list, with an expected street price of around $850 it has a few additional features. First, as mentioned above, it can be genlocked, so you can eliminate the drift issues. Second, unlike the Fuse card, it has its own audio inputs, which sample at 48KHz.
These inputs are significant because the newest Mac G4s do not have any audio inputs. This means that if youre using a Fuse card on a new G4, and you want to digitize audio into Final Cut Pro, Adobe Premiere or other video editing application that doesnt support Pro Tools hardware, youll need a USB or FireWire audio device. The Igniter cards, including the LT version, provide two audio inputs. (For most people using the Fuse with Pro Tools, though, youll want to capture your guide track directly into Pro Tools, and not through Final Cut Pro, anyway.)
Farewell to the Fuse Card
In researching this article, I spoke with Daryl Hock of Aurora Video Systems, who mentioned that the company is planning to discontinue the Fuse card within the next year. This is partly due to supply issues with some of the components that make up the Fuse, but it is also a response to Apples decision to eliminate the built-in audio on G4s. In addition, it is likely that Fuse drivers will not be available for use with Mac OS X. Daryl expects that the new Igniter LT will be an effective replacement for the Fuse.
The Igniter works at different resolutions than the Fuse card. For example, the full-resolution setting for NTSC on an Igniter card is 720x486, while on a Fuse card, it is 640x480. Both the Igniter and the Fuse use the Aurora MJPEG codec, though, so you can play Fuse-digitized material through an Igniter card. Because of the differences in pixel size, though, the image may be slightly elongated from side to side, but this should not be a concern when using the video as a reference for cutting sound. (The reverse is not possible you cant play higher-resolution Igniter-digitized material back through a Fuse.)
Does Your Video St-st-stutter on Playback?
Because of a bug in the way Pro Tools 5.1 handles QuickTime video, you may notice some jerky, stuttery playback. While Digidesign knows about the bug and plans to address it in future releases, you can do some things now to minimize the problem:
- Make sure you are capturing from a stable video source. While most consumer VHS decks should work, a few are just too jittery and unstable, and the result is corrupt video that will not play back smoothly. (In some cases, it could even crash your Mac!) If you are getting black frames or garbage frames, try digitizing from a different deck, or run the signal through a time base corrector.
- Lower your data rate to less than 800K per second, and perhaps even as low as 500K per second. At these low data rates, youll want to be at a low resolution, such as 320x240.
- Use only single field mode when capturing. If you are working at 320x240, this should be automatic. To make sure, select Options in the Compression Setting window of the Capture, Sequence, or Export Settings Preference in Final Cut Pro or Premiere (Figure 1). Instead of Automatic, set this to Manual and One Field.
- If your video gets stuttery while playing, stop, then play again. This should clear it up. If this doesnt help, try deleting the movie track in Pro Tools, and re-import the movie file.
More on Working with Pulldown
In the last issue, I briefly discussed a problem using digital Quicktime video in a pulled-down Pro Tools session. Unfortunately, the solution was not presented correctly you need to select a 30 fps rate when exporting, not when capturing. Let me clarify the procedure I use to prepare video for a pulled-down session.
If you are working with a Pro Tools project, and you are in pull-down or 30-fps mode (i.e. 29.97 with the pull-down button checked, or 30 fps without a pull-up), then your QuickTime video as captured will not play back in sync. This is because when you set a Pro Tools session to "Pulldown", it will slow the playback of the Quicktime video by .1%. If youre using normal, 29.97 Quicktime video, it will be slowed to a non-standard speed. To get around this, we fool Quicktime into thinking that the movie should be played at 30-fps. Then, when Pro Tools slows it down, it will run at a proper 29.97.
To do this, we export the movie from Final Cut Pro (either as a reference movie, or self-contained) at 30-fps. You can then import this movie into a pulled-down session, and the video will play back in proper sync.
To do this, select Export > Final Cut Pro Movie. Then set the export settings to 30 fps (Figure 1). If you dont select "Make Movie Self Contained," you will have a "reference movie" that will point back to the QuickTime video that you captured at 29.97. But, dont worry, it will play back correctly in the pulled-down Pro Tools project. Remember that with a reference movie, you should not delete the original media that you captured, because the reference movie contains no video of its own.
Go to Part Four