ELSA WINNER 2000/Office, User Manual

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All About Graphics
WINNER 2000/Office
37
Video Formats: Compressors At Work
Recording videos on your hard disk can quickly take up a great deal of its capacity. The
amount of space required depends directly on the resolution and on the data format. The
Video for Windows driver support the formats RGB16 and YVU9. Especially noteworthy
is the video compression technique developed by ELSA.
RGB16
This data format works in RGB color space. 5 bits/pixel are required for each of the three
color components red, green and blue, and another 1 bit/pixel is required for the filling.
This means that a total of 16 bits/pixel, or 2 bytes/pixel, are required for storing one
frame of video. The color resolution of RGB16 pictures is similar to RealColor under Win-
dows. The advantage of RGB16 is that this format can be directly “understood” by Win-
dows. The disadvantage is the large amount of storage space required. With a
resolution of 320x240 pixels, a single picture takes up 150 kilobytes, and with a resolu-
tion of 640x480 pixels, four times the capacity, or 600 KB per image, is required.
YVU9
YVU9 requires less space with 9 bits/pixel. This format works in YVU color space and
provides 256 gray shades per pixel in comparison with just 32 gray shades with RGB16.
The compression of these files is achieved by reducing the color resolution. The human
eye is more sensitive to differences in brightness than to differences in color, which
means that the compressed YVU images are, qualitatively, no different to those which
are not compressed. A YVU9 picture at 320x240 resolution takes up about 84 KB. A
YVU9 picture with a resolution of 640x480 pixels requires four times the capacity, or 336
KB per image.
When processing YVU9 video you should use the 'MainActor' program. Other video pro-
cessing programs frequently do not support this format.
ELSA Compression
The ELSA video compression technique reduces the data quantity even further. A special
process stores just 3 to 5 bits per pixel. Like YVU9, the ELSA video compression works
in YVU color space. The compression rate depends on the type of images being com-
pressed. Images clean of interference can be better compressed than noisy ones. Large
unchanging areas, uniform brightness and low color variation also enable a better com-
pressed than with complex images. A frame with 320x240 pixels compressed with the
ELSA technique takes up about 48 KB. A frame with 640x480 pixels generally reaches a
higher rate of compression than with 320x240 pixels, and takes up approximately 120 KB.
Your computer carries out the ELSA video compression in real time while you record the
video. Utilizing the ELSA compression presents you with several advantages: