With Digital Video Quality Analyser R&S DVQ, the assessment of picture quality according to subjective criteria becomes an objective realtime measurement method. Picture quality is assessed from artefacts produced by digital compression. The method is based on the analysis of video data and can thus also be used where no reference video material is available. To this end, the optional PC software Quality Explorer™ is available, allowing complete display and analysis of all coding data as well as convenient remote control of DVQ and display of the recorded quality data.
The increasing use of digital, data-compressed TV signals calls for monitoring and assessment of the picture quality. Picture quality assessment is very strongly influenced by the subjective perception of the human eye.
The unique combination of realtime capability and independence from a reference signal make DVQ an indispensable tool in the quality assessment of digital, DCT-coded video sequences.
DVQ is a tool that ideally satisfies both requirements. It determines the picture quality in relation to digital compression and evaluates the results according to the subjective criteria of visual perception.
The method adopted for determining the quality is based on the analysis of DCT-coded video data applied to DVQ in a MPEG2 transport stream. The additional SDI input also allows evaluation of decompressed video data.
Another important feature is quality analysis being performed in realtime so that any potential quality degradation can immediately be recognized and remedied. Moreover, this method allows long-term recording, monitoring and evaluation of picture quality.
Representation of quality levels
The intermediate values determined by video data analysis are differentiated according to luminance (Y) and chrominance (C b and C r) (DVQL-U). In a further automatic processing step the quality values are assessed according to the subjective masking effects produced by high temporal and/or spatial activities of the picture. The result of analysis is a reproducible quality level (DVQL-W) from “excellent” (100) to “bad” (0) on a SSCQE scale (see box) that is optimally adapted to the subjective picture perception.
Quality scale for single-ended (SSCQE) subjective assessment of picture sequences
The four parameters obtained can be read out in the following display modes:
- Bargraph (see front view of DVQ)
- Numeric display
- Long-term profile (FIG 3a)
- Histogram (FIG 3b)
For long-term recording of the quality levels, a time between 5 seconds and 5 hours can be selected.