For high sampling rate in Gs/s of scope passing data to fpga ,interpolation will be used , for a 8 bit ADC , multiple and sum in sinc interpolation will result in 16 bit data . 255 pixel of lcd is representing 8 bit data,but after interpolation 16 bit is comes out , how to put this 16 bit into 8 bit "heights" ?
but the number represent +32768 to -32768 , 8 bit number is +128 to -127 , just use the higher 8 bits is an easy job, how to understand its meaning ? can kripacharya give me an example ?
Did you check the effect of sinc interpolation on real oscilloscope signals? In my view it's rather a theorectical concept than a practical method for presentation of time domain data. I remember an early digital oscilloscope from HP that actually performed sinc interpolation of display sampled data. As a result, you got funny oscillations with monotonous steps. The presentation of the new instrument caused big laughter in the audience.
Sinc interpolation corresponds to a low-pass filter with rectangular shape. This "ideal" filter may be appropriate for small band signals, but it's rarely useable for wide band signals analyzed in time domain. A CIC filter in contrast has a wide transition band and may introduce an unwanted bandwidth reduction. What you probably want is something similar to a bessel or butterworth filter with no or little overshooth in step response. I wonder if recent oscillocopes are using interpolation filters or e.g. spline interpolation of the waveforms?