TABLE OF CONTENTS In addition to encoding and decoding MPEG, NTSC/PAL and many other types of video, a typical system usually requires considerable additional video processing.
Since many consumer displays, and most computer displays, are progressive (noninterlaced) , interlaced video must be converted to progressive ("deinterlaced"). Progressive video must be converted to interlaced to drive a conventional analog VCR or TV, requiring noninterlaced-to-interlaced conversion.
Many computer displays have a vertical refresh rate of about 75 Hz, whereas consumer video has a vertical refresh rate of 25 or 29.97 (30/1.001) frames per second. For DVD and DTV, source material may only be 24 frames per second. Thus, some form of frame rate conversion must be done.
Another not-so-subtle problem includes video scaling. SDTV and HDTV support multiple resolutions, yet the display may be a single, fixed resolution.
Alpha mixing and chroma keying are used to mix multiple video signals or video with computer-generated text and graphics. Alpha mixing ensures a smooth crossover between sources, allows subpixel positioning of text, and limits source transition bandwidths to simplify eventual encoding to composite video signals.
Since no source is perfect, even digital sources, user controls for adjustable brightness, contrast, saturation, and hue are always desirable.
When two 8-bit values are multiplied together, a 16-bit result is generated. At some point, a result must be rounded to some lower precision (for example, 16 bits to 8 bits or 32 bits to 16 bits) in order to realize a cost-effective hardware implementation. There are several rounding...
