1, group when delay lack fidelity
Group when delay lack fidelity belong to a kind of linear lack fidelity, it basically is introduced by filter. This kind lack fidelity will cause undesirable effect to TV picture quality. If be in program of transmission monochrome television, what can make the image picture that return produces edge and relief effect is excessive and lack fidelity; In program of transmission colour television, will create the appearance with luminance signal and chroma signal bad coincide, the chromatically in be just as color to presswork forbids in that way lack fidelity.
Alleged when delaying is the transmission time that shows signal passes transmission passageway place to need.
The mathematical expression of amplitude modulation wave is: U=u (1+m*cos ω 1t) 2+ ω of ω of 2t+1/2m*u[cos(of Cos ω 2t=u*cos ω 1)] of ω of 1)t+cos(ω 2- among them M is modulation coefficient, ω 1 it is frequency of modulation signal horn, ω 2 it is frequency of horn of carrier wave signal.
The mathematical expression after carrying transmission network is: ψ of Δ of U=k*u[1+m*cos(ω 1t- ) ] ψ of *cos(ω 2t- )
ψ of =k*u*cos(ω 1t- ) + 2+ ω of 1/2m*k*u{cos[(ω 1)t-(ψ + Δ ψ ) ] + ψ of 1)t-(of ω of Cos[(ω 2- - Δ ψ ) ] }
=k*u*cos(t- ψ / ψ of 2(t- of ω 2)+1/2m*k*u{cos[ω / ψ of Δ of 1(t- of ω 2)+ ω / ψ of 2(t- of ω 1)]+cos[ω / ψ of Δ of 1(t- of ω 2)- ω / ω 1)]}
K is the transmission coefficient of the network, ψ , (ψ - Δ ψ ) , (ψ + Δ ψ ) the phase shift after be carrier frequency and fluctuation Bian Pin to carry a network respectively; ψ / ω 2 be carrier frequency heft when delay; ψ / ω is delayed when the 1 sth resembling a net that it is a bag, if pursue,Q-1 place is shown.
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This shows, when amplitude modulation wave carries a network, appeared carrier frequency and bag sth resembling a net two when planting, delay. But, as close as picture quality relationship is not phasic when delay, when including sth resembling a net however, delay. Of the signal content that because bag sth resembling a net is report,transmits. If the network is in 2 ± of ω phasic character is linear inside 1 limits of ω , so although produced a package,delay when subsidiary channels in the human body through which vital energy, but error is not extended when occurrence bag sth resembling a net. But actually, the phasic frequency character of the network always is nonlinear, if pursue,Q-2 place is shown. Similar ground regards phasic character small paragraph is linear can be in only at this moment inside very narrow frequency range, paragraphs of this are small linear slope is equal to the transmission time of the signal inside limits of a paragraph of small frequency, mathematical expression is: ψ of τ = Δ (ω of ω 2)/ Δ 2 → of 2 ω extraction Δ the limit of 0, :
2 → of ω of Δ of τ =lim 0[Δ ψ (ψ of 2]=d of ω of ω 2)/ Δ (ω 2)/d ω 2 at this moment τ expresses with ω 2 for the center infinite inside narrow frequency band, signal synthesizes the bag sth resembling a net of wave to pass the transmission time of the network. Because bag sth resembling a net is You Qunpin,normally signal comprises, when including sth resembling a net so, delay call again group when delay.
Apparent, by D ψ (ω 2)/d ω 2 affirmatory group when delay τ , it is the slope that the curve nods the phasic frequency character that graph Q-2 place shows each, and the function that is frequency. The slope of the curve of phasic frequency character with different frequency corresponding place is different, namely group when delay a cost unequal. As a result of this kind of reason, caused place to occupy each frequency inside frequency band group when extend the error between numerical value. Error is bigger, those who make reproduce image group when delay lack fidelity bigger. So, what we say group when delay lack fidelity point to namely this kind group when the deviation cost that delay. Thinking draft
- 2, differential and phasic: Differential and phasic it is to show the luminance signal extent that concerns with chroma changes the phasic change of the heft of chromatic carrier wave that causes. In NTSC system, the change of horn of chromatic signal vector represented tonal change, differential is so phasic it is very serious to the influence of signal. And because PAL system was used pour photograph technology line by line, so oneself compensation action makes the change of coloring degree of saturation replaced tonal change. As a whole, differential and phasic it is the extent variation that uses descriptive luminance signal a parameter of tonal to color influence. Thinking draft
- 3, differential gain: Differential gain is to show the extent change of chroma signal follows the function concern that changes about luminance signal extent, it is the change of chromatic degree of saturation to the influence of image. Say simply: The metabolic to chromatic degree of saturation influence that differential gain is luminance signal amplitude.
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