Calibrating the timecode signal input

Transcription

1 Chapter 5 Calibrating the timecode signal input Computer hardware can introduce an offset between the timecode signal and the video signal, which causes the timecode and video to be offset when they are captured. If the timecode you capture doesn t match the timecode on your video deck, you ll need to set a timecode offset. To do this, you ll need a test tape with timecode visible in the frame (a window dub), or you ll need a deck or camcorder with a timecode display option. To calibrate timecode: 1. Capture video from the window dub test tape or from another tape with the timecode display option for your deck turned on (Figure 5a.1). 2. In the first frame of your test capture clip, compare the burned-in timecode visible in the video frame with the timecode value that appears in the Viewer s Current Timecode field (Figure 5a.2). (If you use the display option, the number will appear in your camera s viewfinder or on your external monitor.) 3. Calculate the duration of the offset by subtracting the Current Timecode field s value from the burned-in timecode value (Figure 5a.3). If the timecode value in the Current Timecode field is less than the burned-in timecode value, you should get a positive number for the offset duration. If the Current Timecode field s value is greater than the burned-in timecode value, you should get a negative number. Figure 5a.1 Capture a test clip. Figure 5a.2 Compare the burned-in timecode visible in the video frame with the timecode value in the Viewer s Current Timecode field. Figure 5a.3 The burned-in timecode minus the Current Timecode value equals the duration of the offset. 5-1

2 Capturing Video 4. You ll need to edit your Device Control preset to enter the timecode offset. Choose Edit > Audio/Video Settings; then click the Device Control Presets tab. 5. On the Device Control Presets tab, select your current Capture preset (it should be checked); then click Edit. 6. In the Device Control Preset Editor window, enter the calculated duration of the offset in the Capture Offset field; then click OK (Figure 5a.4). 7. Repeat the test to double-check your work. Tip You should recheck your timecode calibration every time you switch video decks or cables! If you regularly switch between a couple of decks, you can incorporate each deck s timecode offset into a customized Easy Setup. Simply switch Easy Setups when you switch decks. It s that simple. Figure 5a.4 In the Device Control Preset Editor window, enter the calculated duration of the offset in the Capture Offset field. 5-2

3 Chapter 5 Calibrating capture settings with color bars and audio tone When you capture video that is already in a digital format (such as DV), FCP makes a straight digital-to-digital transfer, so you won t be able to adjust color and brightness on digital video in the log and capture process. That s why the adjustment sliders on the Clip Settings tab are disabled when a DV Capture preset is selected. Once your material has been captured, however, you can use FCP s excellent color correction filters to tweak the image to your (or your client s) satisfaction. See Using Color Correction Filters in Chapter 16 for more information. If you are capturing video from an analog video format or using an analog-to-digital capture card with FCP, your setup procedure should include the calibration of your capture settings using color bars and an audio tone from your source videotape. Calibrating a tape to color bars and an audio tone matches the color and audio level settings for a whole tape to the settings present when that tape was recorded. The settings you make are saved with each logged clip and applied when you capture the clip. FCP Protocol: Luminance Measurement Analog vs. Digital Avideo image s luminance (brightness) is measured differently in the analog video domain, where it s measured in IRE units, and in Final Cut Pro s digital domain, which is governed by the International Telecommunications Union (ITU) standard for digital video. When you use FCP s waveform monitor and vectorscope to examine your analog video s luminance levels, keep in mind that the FCP waveform displays the luminance level as a percentage; it does not display luminance levels in the analog video scale of IRE units. Your analog capture device will determine the black IRE level of its output (a switch on the device should allow you to select a black level of 7.5 IRE or 0 IRE). Whether your analog video input is set to output a black level of 7.5 IRE or 0 IRE, black is always represented on FCP s digital waveform scale as 0 percent, and white is represented as 100 percent. (That s percentage not IRE units.) When it s time to output your video to an analog video device, the IRE settings of the analog video device that s converting your digital video back to analog will control the final IRE black level. Confusing? You bet. If your analog video levels are critical to your project, you ll need to monitor them after they ve been converted to analog with an external hardware waveform monitor inserted at the analog output of your video device or capture card. There is much more to be learned about analog-to-digital video capture. See page III-535 of Apple s Final Cut Pro User Manual PDF, and take a look at Final Cut Pro: About Luminance (article ID 60864) at the Apple Support site: www/info.apple.com/kbnum/n

4 Capturing Video Figure 5a.5 Use the Log and Capture window s transport controls to play the color bar portion of your tape. Figure 5a.6 Click the Video Scopes button. Asingle calibration operation per tape may be enough, but if you need to, you can also use the Clip Settings tab in the Log and Capture window to customize settings for individual clips. Customized clip settings will be saved with that clip. Final Cut Pro includes a waveform monitor and a vectorscope that let you see adjustments and examine the quality of the incoming signal. You make these adjustments on the Clip Settings tab. This procedure will be easier if you record at least 30 seconds of standard color bars on each tape to use when making baseline adjustments. To adjust clip settings with bars and tone (non-dv only): 1. Choose File > Log and Capture. 2. In the Log and Capture window, use the transport controls to play the color bar portion of your tape (Figure 5a.5). The tape must be playing for the measurements in the waveform and vectorscope to be accurate. 3. Click the Clip Settings tab to open it. 4. On the Clip Settings tab, click the Video Scopes button (Figure 5a.6). The waveform monitor will be updated only while the Log and Capture window is active. continues on next page 5-4

5 Chapter 5 5. Use the Waveform Monitor and Vectorscope window (Figure 5a.7) to review and calibrate the following: Adjust the black level so that the black reference bar in the waveform monitor is at the desired level. The waveform monitor displays the luminance and chrominance values of the incoming signal. The vertical axis displays the dynamic range of the signal from black at the bottom (0 percent) to white at the top (100 percent). If black level and white level controls are not available, use the brightness and contrast controls. Adjust the white level so that the white reference bar in the waveform monitor is at the desired level (100 IRE for a 100 percent white reference bar). Adjust the hue so that the ends of the lines in the vectorscope are as near the color target boxes as possible. The diagonal line marker FT is the flesh tone target. All flesh tones should center around this line. The vectorscope displays the hue and saturation values of the incoming signal. The hue is represented by the angle of a line within the circle (its radial position). The saturation is represented by the length of the line from the circle s center point. The vectorscope displays targets for the optimal values for the six primary colors (red, green, blue, yellow, magenta, and cyan) in a standard color bar pattern. Adjust the saturation so that the ends of the lines in the vectorscope are as close as possible to the center of the target boxes. Use the transport controls to shuttle the tape to a portion with a 1 khz audio reference tone; then use the Gain slider to adjust the audio signal to 0 db or so that it does not peak into the red areas of the audio meters. 6. After you ve adjusted your settings, close the Waveform Monitor and Vectorscope window before capturing. Figure 5a.7 Use the Waveform Monitor and Vectorscope window to review and calibrate image-quality parameters. This procedure is for analog-to-digital captures only. 5-5