Conformance
The following information is intended to assist companies wishing to introduce DTT products into the UK market. The requirements are based on:
- The DTG D Book, Chapter 22, “Receiver Requirements” *
- The MHEG-5 UK Profile Specification v1.06 *
- The BERR Digital Tick logo quality requirements
- DTG Functional Specification for Digital TV Recorders v1.1 *
Items marked * are available from the DTG Publications page by email. Registration is required.
The receiver testing carried out by DTG Testing Ltd is based on these requirements.
Please address any queries concerning this information to DTG Testing Ltd: testing@dtg.org.uk
Summary Table
| Test Suite | Current Version | Notes |
|---|---|---|
| RF performance table | As D-Book v5 | Target performance figures determined by DTG RF Sub-group |
| UK DTT SI/PSI | 1.5 | Revised mandatory requirements under consideration by DTG SI Test Suite Group |
| MHEG-5 | 3.0.2 | Conformance with v3.0.2 test suite required from August 2008 |
| Digital TV Recorder | 1.6 | Group 2 functionality is now required for Freeview Plus trade mark licence (9/2007) |
| Time exclusive services | 1.0 | |
| AFD | 1.0 | Test Card M can be used as an alternative |
| Basic subtitles | 1.0 |
RF Performance
RF performance is crucial to satisfactory operation of a receiver and the following performance figures should be met or exceeded by all DTT products. There are two sets of performance figures: one set applies to measurements made on bit error rate (BER) and the other applies when the measurements are made using the criterion of the onset of visible picture impairments as the failure point. Since we are concerned with the viewer experience, it is the latter set of performance figures that are used.
A method for making the RF performance measurements is contained in the D Book.
DTG Performance Targets: Onset of picture failure
| Parameter | 2K | 8K | ||
|---|---|---|---|---|
| 64Q 2/3 | 16Q 3/4 | 64Q 2/3 | 16Q 3/4 | |
| RF Sensitivity: CH 21 | - 79.2 dBm | - 83.4 dBm | - 79.2 dBm | - 83.4 dBm |
| RF Sensitivity: CH 45 | - 79.2 dBm | - 83.4 dBm | - 79.2 dBm | - 83.4 dBm |
| RF Sensitivity: CH 68 | - 79.2 dBm | - 83.4 dBm | - 79.2 dBm | - 83.4 dBm |
| Performance with AWGN | 17.9 dB | 13.8 dB | 17.9 dB | 13.8 dB |
| Protection ratio for co-channel PAL | + 2.0 dB | - 2.0 dB | + 2.0 dB | - 2.0 dB |
| Protection ratio for N+1 adjacent channel PAL | - 37.0 dB | - 39.0 dB | - 37.0 dB | - 39.0 dB |
| Protection ratio for N-1 adjacent channel PAL | - 37.0 dB | - 39.0 dB | - 37.0 dB | - 39.0 dB |
| Protection ratio for Image channel PAL | - 48.0 dB | -.52.0 dB | - 48.0 dB | -.52.0 dB |
| Protection ratio for N+1 adjacent channel DVB-T | - 28.3 dB | - 30.3 dB | - 28.3 dB | - 30.3 dB |
| Protection ratio for N-1 adjacent channel DVB-T | - 28.3 dB | - 30.3 dB | - 28.3 dB | - 30.3 dB |
| Performance with short delay echoes | < 22.2 dB | < 19.5 dB | < 22.2 dB | < 19.5 dB |
| Performance with long delay echoes | < 22.2 dB | < 18.0 dB | < 22.2 dB | < 18.0 dB |
| Performance with a single echo | < 23.0 dB | < 22.0 dB | < 23.0 dB | < 22.0 dB |
SI Performance
The DTG SI/PSI Test Suite is used to determine conformance with the D Book requirements for SI and PSI processing in a DTT receiver, as set out in Section 8 of the D Book.
The current version of the SI/PSI Test Suite is v1.5 and the associated documentation is also v1.5.
Copies of v1.5 have been sent to existing licensees: if your organisation is a licensee and you have not received a copy, please contact DTG Testing immediately.
Work currently in progress in the DTG SI Test Suite Support Group is expected to lead to a clear definition of the criteria for acceptable performance. In accordance with its Terms of Reference, the DTG SI Test Group has determined a minimum set of functions that a receiver must support in order to be considered to meet the performance standard for the grant of the Digital Tick logo licence. The results template in the SI/PSI test suite will reflects this.
As this is a new development, manufacturers have asked for a transition period in which to modify their product software to meet these functional requirements. It has been agreed that the date on which meeting at least the minimum requirements become mandatory will be announced shortly but will be no sooner than 1st April 2008.
In the meantime, the results presented in product reports from DTG Testing should be regarded as advisory. They indicate what mandatory functions are, or are not, being implemented correctly in the product. The report template is being modified to make this clear.
MHEG-5
For demonstrating the conformance of the MHEG-5 engine in a DTT receiver to the MHEG-5 UK Profile v1.06 (which has been a requirement since September 2006), the DTG MHEG-5 Test Suite v3.0.2 is used. 100% conformance is required.
Existing licensees of the MHEG-5 test suite should have received, and be using, the upgraded test suite as copies have been sent to the address registered with DTG Testing Ltd in the End User Licence Agreement. If your company does not have the upgrade, please email David Bradshaw at dbradshaw@dtg.org.uk for a copy.
Manufacturers and product developers not yet licensed to use the test suite should contact David Bradshaw for further information.
Widescreen Switching and Active Format Descriptors
Receivers must conform to section 3.4 and 3.4.2 of the D Book. This can be demonstrated through the use of:
- the appropriate video streams in Test Card M or
- the DTG AFD test suite.
In the latter case, a results sheet obtainable from DTG Testing should be used.
A new DTG AFD test suite is under development and is expected to be available from DTG Testing early in 2009. For further information, please contact David Bradshaw at dbradshaw@dtg.org.uk.
Time Exclusive Services
Receivers must handle the transition between the active and inactive states of a time exclusive service in an orderly fashion, presenting clean transitions into and out of video, audio and MHEG streams without presentation of any content or application not intended for the selected service. Conformance can be demonstrated by use of the DTG Time Exclusive Services test suite v1.0.
Subtitles
At the present time a basic subtitle test stream is available. This tests the colour look-up table, the positioning of subtitle rows on the screen and the timing offset between video and subtitle channels.