2024-01-22 Multimedia Systems

CS576 Multimedia Design

To capture everything, you need to sample at twice the maximum frequency.

The bit rate is how many bits go out per second. It's samples per second times bits per sample, and it ties directly to network throughput.

Take CD audio. It samples at 44.1 KHz with 16-bit quantization, so the bit rate comes out to 705.6 Kb/s per channel. Raise the sampling rate and the bit rate goes up. Use more quantization bits and it goes up too.

Linear Time Invariant

Say we have a multimedia system $x(t) \rightarrow f \rightarrow y(t)$.

If $y_1 = f(x_1)$ and $y_2 = f(x_2)$, then $f(c_1x_1 + c_2x_2) = c_1y_1 + c_2y_2$

Fourier Transform

The Fourier Transform $X(f)$ of a signal $x(t)$ tells you how the energy of $x(t)$ spreads across frequencies $f$. If the highest frequency in $X(f)$ is $B$, we say $x(t)$ is Band-Limited to $B$.

A filter is an operator you can describe by its frequency response $H(f)$. The output's transform is $Y(f) = H(f)X(f)$, so the band $B_y$ of $y(t)$ can't be wider than the filter's band $B_h$. Filters come as low-pass, band-pass, or high-pass.

Spatial Aliasing

• Moire lines

Temporal Aliasing

• Helicopter Blades