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cartTutorials a Safe Harbor blogLive Capture using Matrox MXO2 Mini
Today’s handheld HD camcorders offer amazing quality for their cost and size, but there is a price to be paid for the portability - the video is captured using compression. Without compression, the video files would be so large that the camera’s recording capacity would be used up in a matter of minutes! There are several types of compression that can be applied to reduce the overall size of the video file. The first thing to go is color resolution. When all the color information is kept in a digital video file, it is referred to as having 4:4:4 color. Depending on the HD recording format, color info may be reduced to 4:2:2 or 4:2:0, and the human eye doesn’t readily discern the difference. 4:2:2 color is an acceptable compromise for most work and is better than 4:2:0 color. Next, some formats actually reduce the horizontal resolution of the signal before compression. HDV reduces 1080 HD video from 1920 x 1080 to 1440 x 1080 pixels, while DVCPRO HD reduces the signal down to 1280 x 1080! The average viewer may not miss the extra pixels, but for broadcast work, it is preferable to maintain full-raster HD whenever possible. After reducing the color resolution and possibly the horizontal resolution as well, the remaining signal is further compressed, with MPEG-2 used for HDV and XDCAM EX, or H.264 for AVCHD formats. Compression uses a complex mathematical formula to get rid of redundant info in the video, reducing file size. If a large part of a scene has blue sky for instance, each of the blue pixels doesn’t have to be represented individually – they can be lumped together, as in "this whole area is blue". That’s a greatly simplified explanation, but that is basically what happens with compression. While the casual viewer may not notice that the color space is reduced or the image compressed, your editing software certainly will! While color grading, you may encounter banding in the blue sky, where the shade of the sky changes in large steps rather than finer gradations. For green screen work, you may have a hard time getting a clean edge on your key to separate the talent from the background. For instance, a Canon 1080i HDV camera might have a 1920 x 1080 image sensor, but only 1440 x 1080 pixels get recorded to tape, and that’s after the color space is reduced to 4:2:0 and the entire image is encoded to lossy Long-GOP MPEG-2 at a data rate of just 25Mbps.
Recording direct from the live camera to the computer using the MXO2 Mini not only provides a higher quality, but will also save you the time normally required for ingest of material from the camera tape or memory card. It’s important to realize that the higher quality uncompressed feed from the camera’s HDMI output is only available live during the shoot. Once material is recorded in the camera, any video played out the HDMI port has already been compressed at that point. I should also note that the MXO2 Mini is capable of up, down and cross-convert on capture, so maybe you’re filming with a 720p camcorder but need to deliver 1080p. Just set up the MXO2 Mini to convert the incoming video using the 10-bit dedicated hardware scaler to record as full-raster 1920 x 1080 to your hard drive. Besides its flexible capture options, the MXO2 Mini also provides an HDMI output for LCD monitoring while editing, and includes a color calibration utility for reliable color grading even on inexpensive displays. Analog i/o is also included, and the MXO2 Mini with the MAX option provides greatly accelerated H.264 encoding. Whether in the studio or on location, Mac or PC, laptop or desktop, the MXO2 Mini can increase the quality of your productions and offers flexible workflow options to help you get the job done – on a budget you can live with. 0 responses to "Live Capture using Matrox MXO2 Mini"
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