(modified former Question 2/9)
ITU-T has adopted several Recommendations for the transmission of digital
television signals for contribution, primary distribution and secondary
distribution applications. However, a number of issues related to the
measurement, monitoring and control of digital and mixed analogue-digital
television transmission chains still remain to be solved.
- ITU-R has recommended methods for the subjective assessment of picture
quality (see for instance Recommendation BT.500-11). There is a need to confirm
that those subjective assessment methods are equally applicable to the case of
television transmission on digital or mixed analogue-digital chains.
- In the digital domain, ITU-R SG 6 and ITU-T SG 12 and SG 9 have been also
studying together, in a Video Quality Experts Group, the identification of
appropriate parameters and algorithms that are representative of digital picture
quality, as well as the correlation of the objective measurement of those
parameters to the subjective picture quality. This work has resulted in
Recommendations J.143, J.144 and J.247.
- Concerning the measurement of the overall Quality of Experience (QoE), it
includes not only a single impairment of each mono-media but also inter-media
relation and response time of user operation. There is a need to identify the
group of parameters that can provide objective measurement of the overall QoE
and continuous in-service monitoring and control of it along the transmission
chain for digital and for mixed analogue-digital television transmission.
- Concerning transmission of digital signals, MPEG-2 Transport Streams may be
subject to degradation in signal quality (particularly jitter) after transport
over telecommunication networks. This degradation may be caused by inherent
effects of telecommunication networks such as stuffing jitter in PDH networks,
stuffing jitter and pointer actions in SDH networks, or cell delay variation in
ATM-based networks. In order to ensure reliable limits for these effects on
MPEG-2 Transport Streams, enabling safe operation of terminals and equipment at
the end of the chain (e.g. modulators for digital television transmitters if
using SFN networks), standardized templates for maximum permitted signal
deviations are required.
- Another digital video transmission uses packet oriented data format. The
packets may be transmitted not only over IP networks but also SDH by direct
encapsulation and cable networks using cable-modem. It will include packet
transmission delay jitter, packet loss, packet duplication, and packet disorder.
In order to ensure reliable limits for these effects on packet video data,
enabling safe operation of terminals and equipment at the end of the chain (e.g.
buffer verification of video decoders), standardized templates for maximum
permitted signal deviations are required.
- For some objective video quality models to operate effectively, the source and
processed video sequences need to be aligned in the spatial and temporal
dimensions. (In some cases such video registration can be treated separately
from objective perceptual video quality assessment). Furthermore, in order to
test processed video sequences to see if they meet validation test requirements
(e.g., maximum spatial and temporal shifts), reliable methods to measure video
registration are required. Therefore, it would be helpful and necessary to
develop methods for video registration.
- Sometimes there is also a need for calibration methods in order to identify
any modifications introduced into the video signals (e.g. gain and offset).
Study items to be considered include, but are not limited to:
- Are the methods recommended or studied by ITU-R Study Group 6 for
subjective assessment of digital picture quality also applicable to the area of
activity of Study Group 9?
- If they are not, should any different or additional methods for picture
quality assessment be recommended by Study Group 9, as specifically applicable
to impairments introduced by digital or mixed analogue-digital television
- How should the methods developed by ITU-R SG 6, or extended by SG 9, for
subjective assessment be applied to digital or mixed analogue-digital
- Which parameters and algorithms are representative of digital picture quality
and how does the objective measurement of them correlate to subjective picture
quality? (This work is to be carried out in cooperation with the Video Quality
- How should the objective measurement of impairments introduced by digital or
mixed analogue-digital transmission networks be carried out?
- Which network parameters should be used to provide objective measurement of
the overall QoE and should be the basis for continuous in-service monitoring
along the transmission chain both for digital and for mixed analogue-digital
- Which network parameters can be dynamically adjusted for the supervision and
control of the overall QoE in digital television transmission networks and how
can such supervision and control be implemented in operation?
- What are the appropriate jitter/wander values for MPEG-Transport Streams and
packet video demapped from telecommunication networks and what parameter
tolerances need to be specified?
- What methods can be used for video registration of source and processed
sequences for use in objective video quality assessment?
- What methods can be used for video calibration?
- What are the necessary test materials and test signals required for video
registration and calibration?
- What trade-offs are inherent in different registration and calibration methods
with respect to such factors as speed, accuracy and complexity and what are the
effects on accuracy when limited information is available for video registration
- What enhancements to existing Recommendations are required to provide energy
savings directly or indirectly in Information and Communication Technologies (ICTs)
or in other industries? What enhancements to developing or new Recommendations
are required to provide such energy savings?
Tasks include, but are not limited to:
New draft Recommendations should be ready before the end of 2012.
An up-to-date status of work under this Question is contained in the
SG 9 Work Programme.
- J-series, P-series, ITU-R BT-series