Capturing Video to an AVI File

After inserting the videotape in the Digital Betacam and adjusting the video parameters if necessary, open the capture program, configure it, and then start the capture. Contoso will use Amcap or Windows Media 9 Capture because they capture AVI version 2.0 files, which permit file captures exceeding 2 GB. Keep this in mind if you choose another capture program. However, you will find the same types of settings on any capture card.

To capture video, the operator starts the capture program and follows these steps to configure a session:

1. On the File menu, click the Set Capture File command to specify the name and path of the capture AVI file to be created.

2. Select the audio and video capture device sources. The video capture card can be the source for both, or you could capture audio from a separate sound card.

3. Select Preview to display the source video in the capture program. You use preview to configure the video settings on the capture card. During capture, this displays the image that is being recorded. However, preview does not have to be enabled in order to capture.

4. On the Options menu, click Video Format to display the driver properties. These are the settings that affect the capture card directly. The settings are configured as described in the following steps.

5. On the Source tab, the following settings affect the incoming video:

   • For Input, select SDI. The capture card inputs video from the SDI connector, which is connected to the Digital Betacam. Because Contoso is sourcing a digital signal, the capture card does not have to do as much processing (such as color correction). Therefore, some settings are not available. The SDI input can also carry embedded audio. However, Contoso will use the digital audio input. To source from the S-VHS deck, select Composite or S-video.

   • For Video Settings, select Bypass color correction. Color correction processing on the capture card is bypassed because the video signal is digital. Even with bypass turned off, the settings you make to brightness, contrast, and saturation on the driver will not affect the captured video. If you are capturing from a composite or S-video source, you will need to configure these settings. For more information about configuring an analog source, see chapter 15.

   • For Video Standard, select NTSC-M. This is the video standard used in North America. You would select PAL-BDGHI if your source video is formatted using the PAL or SECAM standards.

6. On the Format tab, the following settings affect the video leaving the capture card:

   • For Color Format, select YUV12 planar (I420). This is the standard color format used by Windows Media. The color format of digital video determines the arrangement of the digital information that describes the pixels that make up the images. The RGB32 format reproduces the most accurate image, but the size of a video file created with RGB32 is larger and the bit rate of the video stream is higher. Because Windows Media Encoder will convert the color format to YUV12 planar anyway, there is no point in capturing with a higher-resolution color format. For more information about color formats, see the pixel format sidebar in chapter 1.

   • For Proportions, select CCIR601, which reproduces the image with the same pixel proportions that are in the original Digital Betacam video, known as nonsquare pixels. Standard proportions create square pixels. If you use standard proportions with the Digital Betacam video, the image will appear squeezed horizontally. You should use standard proportions when capturing analog video.

   • For Video Size, select Full, which reproduces a full-size image with nonsquare pixels at 720 x 480 resolution. To cut file size in half, you can capture at 360 x 480 by entering the settings in the Custom Size boxes. This method produces an image that is squeezed to half its width. However, when you create the final Windows Media file, the encoder stretches the image back to normal width. The disadvantage is that image resolution is also cut in half, but often this method of reducing file size produces an image that is acceptable, and the height of 480 pixels enables you to enhance the quality using deinterlacing or inverse telecine, which are described in chapter 2. If file size and bit rate are still too high, you can capture at half size (360 x 240).

     The other tabs of the driver dialog box provide additional settings. However, the Contoso staff will leave the default settings. For more information about these settings, see the documentation provided with the driver or video capture card.

     After making the settings on the Source and Format tabs, close the dialog box.

7. On the Options menu, select Audio Format. The format is configured for PCM audio, 48,000 kHz, 16-bit, Stereo. Uncompressed audio will be captured, with the same sampling rate, bit depth, and number of channels as the digital tape. For analog tape, you can use any setting. However, for the best quality, you should not use a setting lower than 44,100 kHz, 16-bit.

8. Open the mixer by double-clicking the speaker icon in the taskbar or from the Sounds and Audio Devices dialog box. In the mixer properties, open the Recording mixer for the video capture card and make sure the AES/EBU digital audio input is selected. Notice that, when you select the digital input, the volume controls are disabled. As with the video, you cannot make audio level adjustments to an audio signal that is being captured digitally, because you are essentially copying the data from the tape to your hard drive. For analog tape, select analog Line in.

9. On the Capture menu, click Set Frame Rate and make sure the
   Use Frame Rate check box is not selected. Video will be captured at the same rate as the source video.

10. On the Capture menu, click Start Capture. The Ready to Capture dialog box opens. At this point the operator presses the Play button on the Digital Betacam deck. Two to four seconds prior to the start of video, she clicks OK to start the capture. It is easier to delete a second or two of black from the beginning of a capture than to have to recapture a movie because the first few frames were cut off.

11. To stop the capture, press the ESC key. The Contoso operator then renames or moves the capture file, if necessary. If you do not rename or move the file, the capture program will record over it the next time you capture, unless you set a new default capture file name.

During the capture, keep an eye on the capture program status bar. It should display the number of frames captured, elapsed capture time, and the number of frames dropped. If frames are being dropped regularly, stop the capture and troubleshoot the computer. Remember, the capture program drops frames if any part of the data flow chain in the computer is not processing or transferring data fast enough. If computer specifications are adequate, you follow all the guidelines in this chapter, and the computer is operating correctly, the computer should not cause these problems.

You can check the performance of the computer during a capture by opening the Performance Monitor and watching for CPU and memory overload. Dropped frames in a digital capture can also occur if there is a problem with the videotape or VCR. If you suspect that, try capturing through the composite or S-video input.

Amcap and Windows Media 9 Capture were designed to capture uncompressed audio and video quickly and efficiently. If you want to add compression as you capture, you can use another capture program, such as Vidcap32. The Windows operating system comes with a number of codecs that you can apply to data during a capture. Keep in mind, however, that applying compression makes files smaller and bit rates lower, but will require more processing power and can result in more dropped frames.

Also, your capture utility must support capturing files larger than 2 GB, because even a compressed movie will require far more than 2 GB of storage. Vidcap32 does not support files larger than 2 GB.

If you use a capture card and utility that provides hardware compression, keep in mind that you will only be able to play back a hardware-compressed file on a computer on which that model of card is installed. Also, make sure the encoder supports that system of compression before investing in the card.

When the capture is complete, play the file in Windows Media Player and check for quality. Because Contoso is not using compression, the video images should appear with the same resolution and color as they did in the preview window. Also, they should not see any video or audio artifacts, such as blockiness and inconsistency in colors.

The main quality you should look for when checking an uncompressed capture is smoothness of motion. Any jerkiness or stuttering in the motion can be caused by dropped frames. If the number of dropped frames is high, you may want to capture the video again after checking to make sure unnecessary programs and services are closed and the computer is running smoothly. Keep in mind, however, that the video may not play back evenly because of the high bit rate of the uncompressed video.

After Contoso has captured the uncompressed AVI file successfully, they use Windows Media Encoder to compress and encode a new file.