Introduction to the DMB-TH Digital TV Standard Adopted for China:
The DMB-TH or DTMB (GB 20600-2006) is the digital terrestrial television (DTT) standard that is currently applied and used in the People's Republic of China (PRC), including Hong Kong and Macau territories. This mandatory standard will cover both fixed and mobile terminals and will eventually serve more than half of the television viewers in the greater China, especially those in suburban and rural areas.
The standard is being officially called Digital Terrestrial Multimedia Broadcast (abbreviated as DTMB. The standard was formerly named as Digital Multimedia Broadcast-Terrestrial/Handheld and in short DMB-TH). DTMB is an outgrowth of work started and carried out at Jiaotong University (developed ADTB-T, similar to ATSC, which coexists with DVB-T) in Shanghai and Tsinghua University (who developed DMB-T) in Beijing, each of which had hoped to provide the sole technology – but neither of which had the technical or political muscle to achieve that goal, the final decision was to opt for a dual standard and fuse with the TiMi 3 standard, as a direct result of backward compatibility as the exploitation of ADTB-T, DMB-T and DVB-T for HDTV transmission via set-top decoder boxes occurred prior to the final draft of the standard, thus making DTMB a fusion of the two aforementioned standards, the ADTB-T and DMB-T.
The data transmission methodology implemented by the standard is the TDS-OFDM (which stands for "Time Domain Synchronuous-Orthogonal frequency-division multiplexing"), which mainly is a multiple-carrier modulation technology, supporting both single-carrier and dual-carrier modulation schemes. The standard, according to the co-developer of the DMB-T standard with Tsing Hua University, is capable of transmitting "acceptable" signal qualities for the HDTV receiver to be moving at 200 km/h speed. The standard also has the support of mobile digital TV service for handhelds which is absent from typical digital TV implementations in Europe and America. In addition to these, the radius of the area with signal coverage using the DTMB standard is 10 km longer than the European implementation norm., the DVB-T standard. The standard also has the advantages of all the three standards, DVB-T, ADTB-T and TiMi 3 as the DTMB standard is the fusion of three standards.
Despite these advantages, there are also short comings of this standard (as expected with any standard). As the standard supports both, single-carrier and dual-carrier modulation schemes as well as not defining the default video encoding standards, the research and development cost and complexity of the chip IC for this standard will be high, leading to more expensive receiver production. But this is likely to change as production increases and more and more of the population of greater China have reception to such DTT signals. In addition, TV programs bought from overseas which are broadcast in digital TV format may have to do a signal conversion that suits the DTMB environment, as the DTMB standard is slightly different than the original DVB-T and ATSC standards, and is less cost effective.
It is worth noting that in spite of the data transmission methodology of the standard being set, the standard itself does not restrict broadcasters to the use of the certain number of video codecs in transmitting digital TV signals, that means each individual broadcaster will have discretion to utilize any type of video codec provided that the codec in question supports high-definition video, the standard also provides as well for providing subtitles, Electronic Programme Guides (EPG) and interactive features.
The Victor VDA-801 is a DMB-TH (GB 206600-2006 China Standard) DTT HDTV Set Top Box Decoder Tuner for the Hong Kong, Macau and China market. In Hong Kong it is currently selling for HK$1,300 - 1,400. Digital broadcasts in Hong Kong began at 7 p.m. on December 31, 2007. One of the free-to-air television broadcasters.
The Victor VDA-801 DBM-TH HDTV Tuner Technical specifications:
("His Master's Voice")Tuner Section:
Input Frequency Range: 48-862 MHz
Input Level: -25 ~ +20dBm
Input Impedance: 75 Ohms
Demodulation:
DTT Standard: China Digital TV Standard DMB-TH (GB 206000-2006)\
Demodulation: OFDM (TDS-OFDM)
Bandwidth: 6M/ 7M / 8M
Video Decoding:
Standard: MP@HL/ML, H.264 HD/SD
Aspect Ratio: 4:3, 16:9
Video Resolution: PAL/NTSC Auto
Audio Decoding:
Standard: ISO/IEC 131818-3 TR101154
Decoding: MPEG-1 & MPEG-2 layer I and II, AC-3
Output Modes: Left, Right, Stereo
Volume Level: 32 steps
High Definition Output:
Output Format: 1080i, 720p, 576p
High Def. Ports: HDMI / YPbPr / RCA
Digital Audio: S/PDIF output
Ports: S- Video, Audio L & R, Composite Video, RS-232, USB, Ethernet.
Voltage: AC 100 ~ 240V, 50/60Hz 20 Watts consumption
Other Features:
- Dolby AC-3 Audio Decoding;
- Down-mixes 5.1 AC-3 to two channels encoded with Dolby Prologic Surround;
- YPbPr Output - 1080i/720p/576p - 576i;
- HDMI Output - 1080i/720p/576p -576i;
- Simultaneous HD/SD Output (HDMI, YPbPr, CVBS);
- 7 Day Electronic Progeam Guide (EPG);
- Sofware upgradeabole via RS-232 serial port;
- 32 bit colors on screen display (OSD) supported;
- USB 2.0 (Host) connectivity for digital devices;
- Digital Audio Output S/P DIF
HDTV Channels in Hong Kong (as at 29/08/2008):
ATV Channels:
11 Home (Simulcast) 576i (720X576) 16:9 MPEG-2 Entertainment M 1
12 News&Business Channel 3 H.264 News and financial information
13 His TV 3 Sports
14 Her TV 3 Fashion
15 Plus TV 3 Culture and nature
16 World (Simulcast) MPEG-2 Entertainment M 1
17 CCTV-4 4:3 H.264 Mandarin entertainment 37
19 aTV HD 3 1080i (1920X1080) 16:9 Entertainment
SD: 576i (720 x 576), HD: 1080i (1920 x 1080) Aspect Ratio: 4:3 & 16:9
Frequency Range: 598-606 MHz
TVB Channels:
81 Jade (Simulcast) 576i (720X576) 16:9 MPEG-2 Entertainment M 1
82 J2 3 H.264 Youth entertainment
83 2 Interactive Info. Channel 3 Interactive news and financial information
84 Pearl (Simulcast) MPEG-2 Entertainment M 1
85 HD Jade 3 1080i (1920X1080) H.264 Entertainment
SD: 576i (720 x 576), HD: 1080i (1920 x 1080), Aspect Ratios: 4:3 & 16:9
Frequency Range: 582-590 MHz
Below: Bar graph showing the average HDTV reception quality to date around Hong Kong
Being located in Fanling in the northern part of Hong Kong I have an added bonus of receiving 6 additional digital TV stations from nearby China, which other people in the urbanized areas are unable to receive, the stations are:-
Channel: Station:
903 SZTV-1
904 GDTV
905 CCTV-4
906 GD
907 CCTV-1
908 SZTV-2
For my digital source playback, one of my digital to analog converters is the Lite Audio DAC-60 which is a 24bit Vacuum Tube DAC. This is another product which is made in China and I purchased this many years ago when I purchased the u3i phono stage. The sound stage, depth, clarity, timbre and details are unsurpassed and the upper and lower harmonics are hard to beat. This was money well spent for a DAC of Hi-End calibre.
