Final Cut Pro: How to Calibrate Serial Timecode

Unless you're capturing a DV or HD video format via FireWire, the timecode and audio/video signals are received separately by Final Cut Pro. Timecode is captured via the serial device control cable (using RS- 422 format in most cases), while audio/video is captured via the cable connected to the video capture interface (composite, S-video, component, or SDI). Because the signals are separate, they can possibly arrive at different times, causing the wrong timecode number to be recorded onto captured video frames. In the case of formats captured over FireWire, the FireWire cable is used for both.

You can calibrate your timecode and video capture setup by adjusting the number of frames that timecode signals are offset from video input by using the Capture Offset field. Apple-qualified video capture devices include software with pre-configured Easy Setups. The supplied Easy Setups will set the Capture Offset to a correct value for that device and media format when using many VTRs and configurations.

If timecode is an important part of your workflow, it's a good idea to check the calibration prior to beginning a project (see steps below). After the initial accuracy of the timecode is verified, there are a number of factors that might require adjustment of the Capture Offset value:

• Capturing media acquired with unknown or known faulty equipment (for instance, if you did not shoot the video yourself, or if it is otherwise of unknown origin).
• Changes in the type of timecode used during captures (i.e. LTC, VITC, etc.).
• Changing from one make and/or model deck to another.
• Even between two decks of the same make and model, if one is programmed with a different firmware version than the other, there may be slight differences requiring calibration. Many higher end and multi-format capable decks are programmed with firmware that can be updated as revisions are made available. You should consult the literature that accompanied the deck or contact the manufacturer to determine how to identify and update the firmware versions.
• Using a serial device control switcher or router.
• Switching from one port to another.

If you find you are impacted by any of these factors that are causing variance in timecode accuracy, it's a good idea to create separate device control presets, with different Capture Offsets for each configuration. The pre-calibrated presets let you quickly change configurations without having to go though the whole calibration procedure again. For more information the topics covered in this document, see the Final Cut Pro User's Manual.

Note: The Final Cut Pro User Manual suggests that you need to calibrate the video and timecode signal every time you change decks or cables. While it's a good idea to calibrate for different decks, changing cables alone is not likely to affect timecode accuracy.

Determining and Entering the Timecode Offset
You can easily determine if there is a difference between the timecode and video signals by capturing test footage that has timecode "burned in" to the video picture information. By comparing the numbers in the timecode track to the timecode numbers in the video picture, you can determine the offset between them.

If there is an offset, you can calibrate your timecode and video capture setup by entering the number of frames by which the timecode signals are offset from the video in the Capture Offset field of the current device control preset.

To determine the timecode offset:

1. Do one of the following:
   • Create a window-burn (or window dub) test tape for timecode offset testing. You can do this by transferring a tape with timecode to another tape of the same format, making sure you connect an output that can display timecode information visually.
   • Connect the monitor out (or super out) output of your VTR to the input of your video interface. A monitor output is a dedicated output for displaying VTR status information such as a timecode counter superimposed (or "burned-in") over the video information. Some VTRs don't have a separate monitor output, but instead have an option for turning on the deck status display and timecode information on the main output. Enable this option.
2. Capture a clip of video from a tape with LTC (Longitudinal TimeCode) or VITC (Vertical Interval TimeCode) timecode on it.
3. Compare the timecode value recorded in the captured media file (in the Current Timecode field) with the burned-in timecode on the video frame.
   If both timecode values match, then there is no offset, so no adjustment is necessary. If the timecode values do not match, there's an offset and you'll need to compensate for this to capture your video properly.

To enter a timecode offset:

1. Choose Final Cut Pro > Audio/Video Settings.
2. Click the Device Control Presets tab.
3. Make sure your current method of device control is checked, then click Edit.
   If you're using a locked preset, a new copy of the preset is created.
4. Enter a new name and description for this device control preset indicating which camcorder or deck it is calibrated for.
5. Enter a number of frames in the Capture Offset field, then click OK.

Enter a negative number if the clip's timecode track has higher numbers than the burned-in timecode. For example, if the clip's Media Start timecode is 01:00:00:04, and the first video frame has a burned-in timecode number of 01:00:00:00, enter -4 in the Capture Offset field.

After entering the timecode offset, it's a good idea to capture a few more clips and compare the timecode track numbers with the burned-in timecode to determine if the timecode offset you entered is correct.

Some devices may require fractional offsets to maintain accuracy over long batch captures. For example, if in a single clip capture an offset of 2 yields the desired results, but a 10 clip batch capture shows some clips accurate and others not, try an offset of 2.5. You may wish to consult the device documentation for specific tips on which offsets to use.