All of the unbalanced analog and digital video standards, from RF to SDI, use 75 ohm coaxial cables. Even an s-video cable is just a round jacket over two miniature coaxes, one carrying luminance (brightness) and the other chrominance (colour).
DVI and HDMI run high-bit-rate parallel digital video through a set of 100 ohm (+/- 10%) twisted-pair balanced lines.
SCSI, IEEE1394, USB and TOSLINK cables are used for video and audio connections often within the PC environment.
Cables used for audio signals use a diverse range of cables that include figure-8 audio cables, balanced XLR cables, coaxial cables, IEEE1394 cables, OFC speaker cables, TOSLINK cables, and cat-5 cables.
A cable's primary function is to get an electrical signal from point A to point B without meaningful alteration. A "perfect" cable would be able to pass a signal from one end to the other without any alteration to that signal. The extent to which a cable deviates from this ideal is directly related to the physical structure of the cable (and its connectors). All cables do three things to a signal - they (1) attenuate the signal, (2) contribute their own inductive and capacitive reactance and (3) expose the signal to electromagnetic energy from other sources which pollute the signal with noise.
Attenuation of the signal is directly related to the nature and configuration of the conductors. Inductive and capacitive reactance result from the structure of the conductors themselves, their placement in relation to one another, and the nature of the material placed between them. Exposure to outside electromagnetic fields is heavily influenced by the extent and type of shielding provided by the cable.
A well-insulated, well-shielded, physically durable cable, terminated with correctly-shielded, impedance-matched connectors that make sound electrical contact with both the cable and the jack will provide satisfactory performance. Better quality cables will deliver cleaner signals.
Use our audio/video interconnect reference page identify the type of connectors commonly used to terminate a particular cable. Our suggested color code for audio/video interconnects that identifies the role of a particular cable, is based on common industry practice. Our signals reference page explains the different audio/video signal protocols in common use.