Many DSP algorithms introduce delay (ie. think about simple FIR digital filters, like a running averager). They are literally using a "tapped delay line" to pe

Many DSP algorithms introduce delay (ie. think about simple FIR digital filters, like a running averager). They are literally using a "tapped delay line" to perform the computation. There is a tradeoff between the amount of delay you're willing to accept and the "sharpness" of your filters' frequency response. I'm not an expert in TV systems, but this gives the general gist.