Frequently Asked Questions
What is "J.341"?
J.341 is the new ITU-T standard for Objective perceptual multimedia video quality measurement of HDTV for digital cable television in the presence of a full reference.
This Recommendation provides a perceptual video quality measurement method for use in high definition television (HDTV) non-interactive applications when the full reference (FR) measurement method can be used. The full reference measurement method can be used when the unimpaired reference video signal is readily available at the measurement point, as may be the case of measurements on individual equipment or a chain in the laboratory or in a closed environment such as a cable television head end. The estimation method includes both calibration and objective video quality estimations.
The new J.341 standard was developed by leading industry experts and selected in a competition carried out by the Video Quality Expert Group (VQEG) and was adopted by ITU-T SG9. The core of the standard, the perceptual measurement algorithm, was developed by SwissQual AG between 2008 and 2010.Back to top >
How does J.341 measure quality?
The measurement method used in J.341 estimates the visual quality of a test video sequence with respect to its unimpaired reference.
This full reference measurement method can be used when the unimpaired reference video signal is readily available at the measurement point, as may be the case of measurements on individual equipment or a chain in the laboratory or in a closed environment such as a cable television head-end.Back to top >
Is J.341 currently the only standard for HD TV?
J.341 is the only full-reference approach that has official ITU-T approval. Although some vendors might claim an equivalent standard, those approaches are not recognized as standard by the international community.Back to top >
What are the typical applications for J.341?
There are four major areas where this standard can have impact:
- Potentially real-time, in-service quality monitoring at the source;
- Remote destination quality monitoring when a copy of the source is available at the point of measurement;
- Quality measurement for monitoring of a storage or transmission system that utilizes video compression and decompression techniques, either a single pass or a concatenation of such techniques;
- Lab testing of video systems.
Which video formats are covered by J.341?
The model is tested on a wide variety of different frame-rates as used TV applications (29.97fps and 25fps), in interlaced and progressive mode at the resolution 1080 x 1920. content of 720 x 1280 was included in testing by up-sampling it to 1080 x 1920, as this is the typical case for most consumer applications.
Content with 24fps was included in testing but re-played at 25fps.Back to top >
Which types of video encoding can be handled by J.341?
Videos encoded by H.264 (MPEG4 part 10) using either high or main profile, or MPEG2. Supported video bit rates are 1 – 30 Mbps.Back to top >
Which types of transmission errors can be handled by J.341?
The types of errors handled by J.341 include packet errors (both IP and Transport Stream) such as packet loss, packet delay variation, jitter, overflow and underflow, bit errors, and over-the-air transmission errors.Back to top >
What is the difference between J.341 and VQUAD-HD™ or other models available commercially?
J.341 is the only full-reference approach that has official ITU-T approval.
The model used in J.341 is based solely on the already commercially available, model known as VQUAD-HD from SwissQual AG.
No other model was able to achieve equivalent testing scores in all tested categories during comparison by VQEG, and hence the new ITU J.341 standard is based on the VQUAD-HD model provided by SwissQual AG only.Back to top >
What is output of J.341
It is Objective Mean Opinion Score MOS_obj mapped to scale 1 bad to 5 excellent quality.Back to top >