DSP Blockset

Sample Rate and Frame Rate Concepts

The input frame period (T_fi) of a frame-based signal is the time interval between consecutive vector or matrix inputs to a block. This interval is what the Probe block displays when you connect it to a frame-based input line. Similarly, the output frame period (T_fo) is the time interval at which the block updates the frame-based vector or matrix value at the output port. This interval is what the Probe block displays when you connect it to a frame-based output line. (See Inspecting Sample Rates and Frame Rates for more about using the Probe block.)

In contrast, the sample period, T_s, is the time interval between individual samples in a frame, which is necessarily shorter than the frame period when the frame size is greater than 1. The sample period of a frame-based signal is the quotient of the frame period and the frame size, M:

More specifically, the sample periods of inputs (T_si) and outputs (T_so) are related to their respective frame periods by

where M_i and M_o are the input and output frame sizes, respectively.

The illustration below shows a one-channel frame-based signal with a frame size (M_i) of 4 and a frame period (T_fi) of 1. The sample period, T_si, is therefore 1/4, or 0.25 second. A Probe block connected to this signal would display the frame period T_fi = 1.

In most cases, the sequence sample period T_si is of primary interest, while the frame rate is simply a consequence of the frame size that you choose for the signal. For a sequence with a given sample period, a larger frame size corresponds to a slower frame rate, and vice versa.

For information on converting a signal from one sample rate or frame rate to another, see Converting Sample Rates and Frame Rates.

Sample Rates and Frame Rates

Inspecting Sample Rates and Frame Rates