Analog display devices reproduce each frame in the same way, effectively doubling the frame rate as far as perceptible overall flicker is concerned. When the picture capture tool acquires the fields after the other, than dividing up a complete frame after it is captured, the frame rate for motion is effectively doubled as well, leading to smoother, more lifelike reproduction (although with halved detail) of quickly moving parts of the picture when viewed on an interlaced CRT display, but the display of such a signal on a progressive scan tool is problematic.
Video can be interlaced or progressive. Interlacing was invented as a way to reduce flicker in early mechanical & CRT video displays without increasing the number of complete frames per second, which would have sacrificed picture detail to stay within the limitations of a narrow bandwidth. The horizontal scan lines of each complete frame are treated as if numbered consecutively, & captured as fields: an odd field (upper field) consisting of the odd-numbered lines & an even field (lower field) consisting of the even-numbered lines.
In progressive scan systems, each refresh period updates all scan lines in each frame in sequence. When displaying a natively progressive broadcast or recorded signal, the result is optimum spatial resolution of both the stationary & moving parts of the picture. When displaying a natively interlaced signal, however, overall spatial resolution is degraded by simple line doubling�artifacts such as flickering or "comb" effects in moving parts of the picture appear unless special signal processing eliminates them. A procedure known as deinterlacing can optimize the display of an interlaced video signal from an analog, DVD or satellite source on a progressive scan tool such as an LCD Tv, digital video projector or plasma panel. Deinterlacing cannot, however, produce video quality that is equivalent to true progressive scan source material.
NTSC, PAL & SECAM are interlaced formats. Abbreviated video resolution specifications often include an i to indicate interlacing. For example, PAL video format is often specified as 576i50, where 576 indicates the total number of horizontal scan lines, i indicates interlacing, & 50 indicates 50 fields (half-frames) per second.
Video can be interlaced or progressive. Interlacing was invented as a way to reduce flicker in early mechanical & CRT video displays without increasing the number of complete frames per second, which would have sacrificed picture detail to stay within the limitations of a narrow bandwidth. The horizontal scan lines of each complete frame are treated as if numbered consecutively, & captured as fields: an odd field (upper field) consisting of the odd-numbered lines & an even field (lower field) consisting of the even-numbered lines.
In progressive scan systems, each refresh period updates all scan lines in each frame in sequence. When displaying a natively progressive broadcast or recorded signal, the result is optimum spatial resolution of both the stationary & moving parts of the picture. When displaying a natively interlaced signal, however, overall spatial resolution is degraded by simple line doubling�artifacts such as flickering or "comb" effects in moving parts of the picture appear unless special signal processing eliminates them. A procedure known as deinterlacing can optimize the display of an interlaced video signal from an analog, DVD or satellite source on a progressive scan tool such as an LCD Tv, digital video projector or plasma panel. Deinterlacing cannot, however, produce video quality that is equivalent to true progressive scan source material.
NTSC, PAL & SECAM are interlaced formats. Abbreviated video resolution specifications often include an i to indicate interlacing. For example, PAL video format is often specified as 576i50, where 576 indicates the total number of horizontal scan lines, i indicates interlacing, & 50 indicates 50 fields (half-frames) per second.
No comments:
Post a Comment