Ulead MEDIASTUDIO PRO 7, Руководство пользователя

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APPENDIX 401
low compression ratios, such as 2:1 (every one original frame can be
resized down by half). Once you get up to higher ratios such as 10:1 or
even 100:1, noticeable degradation occurs and you would be better off
using another scheme such as MPEG.
MPEG
MPEG has grown out of JPEG but added more sophisticated interframe
techniques to save only the differences between key frames
– called I
frames. Currently there are two standards: MPEG-1 and MPEG-2. MPEG-
1 is designed to produce ½ screen (352x240) 24-bit color, 30 frames per
second video running at approximately 170kbps. MPEG-2 is designed for
full screen (720x480) 24-bit color, 60 field video running at anywhere
between 500kbps to 2mbps. MPEG-2 is set to become the standard for
high quality video playback, particularly over the newer DVD discs.
MPEG.Now
The MPEG.Now software codec promotes superior quality transcoding and
real-time encoding for MPEG 1 and 2. It supports real-time features (e.g.,
direct MPEG capture from IEEE-1394 interfaces).
Aspect Ratio
Aspect ratio is the relative horizontal and vertical sizes of the screen or
image (usually expressed as width:height). If an image has an aspect ratio of
4:3, it means that it is wider than it is tall (which, of course, is mostly the
case for television). It is best to maintain the image’s aspect ratio when
adjusting its size to avoid distortion. It could also be used to represent the
dimensions of a particular image’s display resolution (e.g., if we have a
resolution of 800x600, the aspect ratio is 4:3, or if we have a resolution of
720x480, then the aspect ratio is 16:9). The standard aspect ratio for
traditional television sets and computer monitors is 4:3 while the aspect ratio
for high-definition, wide-screen digital systems is 16:9. More systems can
read 4:3. For the sake of general viewership, 4:3 would be the most advis-
able display aspect ratio to use.