A digital film is created from a series of static images played at a high speed. Digital films are usually around 24 frames per second but can be anything up to around 100 frames per second or more.
Films have a frame rate per second (fps). This is similar to sample rate. HD film is normally 50 or 60 fps. This can also be measured in frequency (Hz). TV and computer screens have a specification in Hz to indicate the frame rate they support.
Digital films also have a bit rate that accounts for the total audio and image data processed every second.
Videos are compressed in order to:
Data lost during the compression process can cause poor picture quality or even random coloured blocks that appear and disappear on the screen. These blocks are called artefacts.