Picture Quality Analysis of Digital TV Signals - Digital Video and Audio Broadcasting Technology - page 200

cedure. It is then attempted to reproduce these subjective methods by
means of objective methods in a test instrument by performing picture
analyses on the macroblocks and using adaptation algorithms.
12.1.1 Subjective Picture Quality Analysis
In subjective picture quality analysis, a group of test persons assesses an
image sequence (SSCQE - Single Stimulus Continual Quality Scale
Method, Fig. 12.2.) or compares an image sequence after compression
with the original (DSCQS - Double Stimulus Continual Quality Scale
Method) and issues marks on a quality scale from 0 (Bad) to 100 (Excel-
lent) by means of a sliding control. The positions of the sliding controls are
detected by a computer connected to them which continually determines
(e.g. every 0.5 sec) a mean value of all the marks issued by the test per-
sons.
Fig. 12.2. Subjective Picture Quality Analysis
A video sequence will then provide a picture quality value versus time,
i.e. a quality profile of the video sequence.