Facsimile and static presentation processing – Facsimile – Specific signal processing circuitry
Patent
1991-08-12
1994-01-11
Groody, James J.
Facsimile and static presentation processing
Facsimile
Specific signal processing circuitry
358142, 358147, H04N 7087
Patent
active
052786498
ABSTRACT:
The black level of the NTSC portion of an EDTV broadcast signal is set to a level N, typically twice as high as the normal 7.5 IRE units. This signal characteristic motivates the viewer or the automatic black level circuits of the NTSC receiver to raise the receiver's black level to about the same N IRE units for optimum reception of the transmitted signal. EDTV enhancement signals are transmitted in the range of +N to -N (for example, +15 to -15) IRE units. Since the NTSC receiver is adjusted to blank all signals below N IRE, the EDTV enhancement signals between +N and -N IRE levels do not trigger the display in the NTSC receiver, thereby maintaining the upper and lower band areas at a uniform black level without unwarranted speckles or other interference.
REFERENCES:
patent: 5075773 (1991-12-01), Pullen et al.
Groody James J.
Harvey David E.
Matsushita Electric Corporation of America
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