Digital Television
Digital TV replaced analog broadcasts with compressed video signals.
Why Digital TV?
Analog TV allocated 6, 7, or 8 MHz channels with significant interference and ghosting. Digital TV uses compression (MPEG-2, later H.264/AVC, H.265/HEVC) to pack multiple HD channels into one channel stream. The result: pristine pictures, no ghosts, and room for data services.
Worldwide DTT Standards Overview
Four major digital terrestrial television (DTT) standards compete globally. Each was developed by different regional consortia and reflects the technical requirements of different regulatory environments.
Standard Regions Channels Modulation Key Feature ───────────────────────────────────────────────────────────────────────────────────────────── ATSC USA, Canada, Mexico, Korea 6 MHz 8-VSB Legacy NTSC channel plan DVB-T/T2 Europe, Africa, Asia 8 MHz COFDM Single-frequency networks ISDB-T Japan, South America 6 MHz BST-OFDM Hierarchical, mobile seg DTMB China, HK, Cuba, Laos 8 MHz TDS-OFDM Time-domain sync
ITU Region Channel Bandwidths
Television channel bandwidth is determined by the ITU region and country, not by the digital standard. Analog channel widths were carried forward into the digital era for backward compatibility with existing spectrum plans.
Region Countries Channel Width
────────────────────────────────────────────────────────────────────
ITU-1 Europe, Africa, Middle East 8 MHz
ITU-2 Americas, Greenland 6 MHz
ITU-3 Asia, Oceania 6 MHz (Japan, Korea)
Australia 7 MHz (VHF), 7 MHz (UHF)
China 8 MHz
India 6 MHz (metro), 7 MHz (others)ATSC (North America / South Korea)
The Advanced Television Systems Committee developed the US digital standard, adopted in the United States, Canada, Mexico, and South Korea. The US completed its analog shutdown in June 2009.
- Modulation: 8-VSB (8-level Vestigial Sideband). Maps 3 bits per symbol using 8 amplitude levels (±7V, ±5V, ±3V, ±1V). The VSB pilot carrier is inserted at 0.3 dB above the suppressed carrier level for coherent demodulation.
- Channel width: 6 MHz (matching US NTSC plan)
- Symbol rate: 10.76 Msymbols/s. Each symbol carries 3 bits (8 levels), yielding a raw bit rate of 32.28 Mbps before FEC overhead.
- Data rate: 19.4 Mbps in a 6 MHz channel (after Trellis Coded Modulation + Reed-Solomon FEC). This carries one 1080i HD stream or up to 6 SD subchannels.
- FEC: Trellis Coded Modulation (rate 2/3) concatenated with Reed-Solomon (207, 188) outer code. The RS code can correct up to 10 symbol errors per 188-byte packet.
- MPEG-2 Transport Stream: 188-byte packets with 4-byte header (sync byte 0x47, PID, continuity counter). The transport stream multiplexes video, audio, and data PIDs.
- Resolution: Up to 1080i (1920x1080 interlaced) or 720p (1280x720 progressive). Legacy NTSC channels carry SD (480i/480p).
US TV Channel Frequencies
All US TV channels are 6 MHz wide. Channel 6 audio carrier at 87.75 MHz overlaps the FM broadcast band — some LPTV stations use this for "Franken FM" radio broadcasts.
VHF Low Band (54-88 MHz)
| Channel | Video Carrier (MHz) | Audio Carrier (MHz) | Band |
|---|---|---|---|
| 2 | 55.25 | 59.75 | 54-60 MHz |
| 3 | 61.25 | 65.75 | 60-66 MHz |
| 4 | 67.25 | 71.75 | 66-72 MHz |
| 5 | 77.25 | 81.75 | 76-82 MHz |
| 6 | 83.25 | 87.75 | 82-88 MHz |
VHF High Band (174-216 MHz)
| Channel | Video Carrier (MHz) | Audio Carrier (MHz) | Band |
|---|---|---|---|
| 7 | 175.25 | 179.75 | 174-180 MHz |
| 8 | 181.25 | 185.75 | 180-186 MHz |
| 9 | 187.25 | 191.75 | 186-192 MHz |
| 10 | 193.25 | 197.75 | 192-198 MHz |
| 11 | 199.25 | 203.75 | 198-204 MHz |
| 12 | 205.25 | 209.75 | 204-210 MHz |
| 13 | 211.25 | 215.75 | 210-216 MHz |
UHF Band (470-890 MHz)
| Channel | Lower Edge (MHz) | Center (MHz) | Upper Edge (MHz) | Notes |
|---|---|---|---|---|
| 14-36 | 470-602 | 473-605 | 476-608 | Standard UHF |
| 37 | 608 | 611 | 614 | Reserved (radio astronomy) |
| 38-51 | 614-698 | 617-695 | 620-702 | 700 MHz band (reallocated) |
| 52-69 | 698-806 | 701-809 | 704-812 | 700 MHz band (reallocated) |
| 70-83 | 806-884 | 809-887 | 812-890 | Public safety |
DVB-T and DVB-T2 (Europe, Africa, Asia, Australasia)
Digital Video Broadcasting became the dominant global standard, used across Europe, Africa, most of Asia, Australia, and New Zealand. DVB-T uses COFDM modulation; DVB-T2 provides 30-50% more capacity through improved FEC and larger FFT sizes.
European UHF Channel Plan (8 MHz)
Most European countries use 8 MHz channels in the UHF band.
Band Channels Frequency Range Channel Width ────────────────────────────────────────────────────────── VHF III 5-12 174-230 MHz 7 MHz UHF IV 21-37 470-606 MHz 8 MHz UHF V 38-68 606-854 MHz 8 MHz
DVB-T Technical Parameters
- Modulation: COFDM (Coded OFDM) with QPSK, 16-QAM, or 64-QAM constellation
- Subcarriers: 1705 (2K mode) or 6817 (8K mode) for DVB-T
- Guard interval: 1/4, 1/8, 1/16, or 1/32 of symbol duration (enables SFN operation)
- FEC: Convolutional coding (rate 1/2, 2/3, 3/4, 5/6, 7/8)
- Data rate: 5-32 Mbps depending on modulation, code rate, and guard interval
DVB-T2 Technical Parameters
- FFT sizes: 1K, 2K, 4K, 8K, 16K, 32K (vs 2K/8K in DVB-T)
- Modulation: Up to 256-QAM (vs 64-QAM max in DVB-T)
- FEC: LDPC + BCH (vs convolutional + Reed-Solomon in DVB-T)
- Data rate: Up to 50 Mbps in 8 MHz channel
- Features: Time-frequency slicing, Multiple-PLP (Physical Layer Pipes)
DVB-T2 Data Rates (8 MHz Channel, 32K FFT, GI 1/128)
| Modulation | Code Rate | Bit Rate (Mbps) |
|---|---|---|
| QPSK | 1/2 | 7.4 |
| QPSK | 3/5 | 8.9 |
| QPSK | 2/3 | 9.9 |
| QPSK | 3/4 | 11.2 |
| QPSK | 5/6 | 12.5 |
| 16-QAM | 1/2 | 15.0 |
| 16-QAM | 3/5 | 18.1 |
| 16-QAM | 2/3 | 20.1 |
| 16-QAM | 3/4 | 22.6 |
| 64-QAM | 2/3 | 30.1 |
| 64-QAM | 3/4 | 33.8 |
| 64-QAM | 5/6 | 37.6 |
| 256-QAM | 3/5 | 36.1 |
| 256-QAM | 3/4 | 45.2 |
| 256-QAM | 4/5 | 48.3 |
| 256-QAM | 5/6 | 50.3 |
Australian Channel Plan (7 MHz)
Australia uses 7 MHz channel bandwidth for both VHF and UHF, reflecting its historical alignment with European standards but with a modified channel numbering scheme.
Band Channels Frequency Range Channel Width ────────────────────────────────────────────────────────── VHF 6-12 174-230 MHz 7 MHz UHF 28-69 520-820 MHz 7 MHz
ISDB-T (Japan, Brazil, South America)
Integrated Services Digital Broadcasting — Terrestrial (ISDB-T) was developed in Japan and adopted throughout most of South America, the Philippines, and Botswana/Angola in Africa. Its defining feature is hierarchical transmission with independent modulation per segment.
- Channel width: 6 MHz (Japan, Brazil)
- Segment structure: 13 segments x 432 kHz each = 5.6 MHz bandwidth within 6 MHz channel
- Hierarchical modes: Hierarchical transmission with up to 3 layers (A, B, C) using different modulations (DQPSK, QPSK, 16-QAM, 64-QAM)
- 1seg: The center segment (segment 0) is used for mobile/handheld reception at lower data rates, while segments 1-12 carry HD for fixed reception
- Audio: AAC-LC, HE-AAC v2 for mobile; MPEG-2 AAC for HD
- Codec: MPEG-2 video for Japan; H.264/AVC for ISDB-T International (Brazil variant)
ISDB-T Transmission Modes
| Mode | Segments | Bandwidth | Typical Use | Max Data Rate |
|---|---|---|---|---|
| Full-seg (HD) | 13 | 5.6 MHz | Fixed home reception | 23 Mbps |
| 1seg (mobile) | 1 | 432 kHz | Mobile/handheld | 416 kbps |
| 2seg | 2 | 864 kHz | Portable/mobile | 1.2 Mbps |
| 3seg | 3 | 1.3 MHz | Handheld HD | 1.8 Mbps |
ISDB-T Regional Variants
Variant Country/Region Video Codec Notes ────────────────────────────────────────────────────────────────────────────── ISDB-T Japan MPEG-2 Original ISDB-Tb Brazil, Argentina, Chile H.264 SBTVD variant ISDB-TInt Philippines, Botswana, Angola H.264 ISDB-T International
DTMB (China, Hong Kong, Cuba, Laos, Pakistan)
Digital Terrestrial Multimedia Broadcast (DTMB) is China's homegrown DTT standard, developed by merging three competing proposals (ADTB-T, DMB-T, and TiMi). It uses Time-Domain Synchronization OFDM (TDS-OFDM), which combines the training sequence with data in the guard interval, enabling faster acquisition and better Doppler performance than DVB-T.
- Channel width: 8 MHz (China), with support for 6 MHz and 7 MHz in export versions
- Modulation: QPSK, 16-QAM, 32-QAM, 64-QAM, and 128-QAM
- FFT sizes: 1 (C=1), 4 (C=3780), 2 (C=1890), 8 (C=945) with PN-sequence training
- FEC: LDPC (BCH outer code) — rates of 0.4, 0.6, 0.8
- Data rate: 4.813 to 32.486 Mbps depending on mode
- Features: Supports fixed, portable, and mobile reception; SFN and MFN networks; multi-level hierarchical modulation
Countries using DTMB: China (including Hong Kong and Macau), Cambodia, Cuba, East Timor (Timor-Leste), Laos, Pakistan, and Comoros.
T-DMB (South Korea — Digital Audio/Mobile TV)
Terrestrial Digital Multimedia Broadcasting (T-DMB) is a mobile terrestrial digital radio and video broadcasting technology derived from DAB (Eureka-147). It operates in Band III (174-240 MHz) and L-band (1452-1492 MHz), primarily for mobile TV and data services in South Korea.
- Modulation: OFDM with DQPSK (audio) or QPSK/16-QAM (video)
- Bandwidth: 1.536 MHz per channel (DAB ensemble)
- Audio codec: MPEG-4 HE-AAC v2
- Video codec: H.264/AVC
- Data rate: Up to 1.2 Mbps for video services
- Coverage: Indoor and mobile reception with SFN support
Compression Technologies
- MPEG-2: Original DTV standard, 19.4 Mbps in 6 MHz. Uses DCT macroblock coding with motion estimation. Supports 4:2:0 chroma subsampling and inter-frame prediction (I, P, B frames).
- H.264/AVC: Better compression, used for streaming and ISDB-T International. Achieves equivalent quality to MPEG-2 at roughly half the bitrate. Introduces variable block-size motion compensation (down to 4x4), multi-reference frame prediction, and CABAC entropy coding.
- H.265/HEVC: 50% more efficient than H.264, for 4K. Uses Coding Tree Units (CTUs) up to 64x64 with recursive quad-tree partitioning. Supports 10-bit color depth and Rec. 2020 color gamut.
- VVC/H.266: Next generation, for 8K and HDR. Further 40-50% bitrate reduction over HEVC with more flexible partitioning (binary and ternary splits).
ATSC 3.0 (NextGen TV — US, South Korea)
ATSC 3.0 is a ground-up redesign of US digital television, moving from 8-VSB to OFDM modulation and adopting IP-based transport:
- Modulation: OFDM with up to 138 subcarriers per segment. Supports QPSK, 16-QAM, 64-QAM, and 256-QAM. Bandwidth: 6 MHz with channel bonding possible.
- FEC: LDPC (Low-Density Parity-Check) + BCH codes, approaching the Shannon limit. Code rates from 2/15 to 13/15.
- Data rate: Up to 57 Mbps in a single 6 MHz channel (vs. 19.4 Mbps for ATSC 1.0). Enables 4K UHD HDR streaming.
- Transport: IP-based (replaces MPEG-2 TS). Uses ROUTE (Real-time Object delivery over Unidirectional Transport) and LMT (Layered Media Transport) protocols.
- Features: Mobile reception, 4K HDR (HLG, HDR10), immersive audio (Dolby AC-4, MPEG-H), hybrid broadcast-broadband, emergency alerting (EAS), and targeted advertising.
Countries Still Using Analog TV
Most countries completed analog switch-off between 2006 and 2015. A small number of countries still use analog terrestrial broadcasting:
Country Status ────────────────────────────────────────────────────── Afghanistan Analog ATV (limited rollout) Belarus Analog still in rural areas Eritrea No digital DTT deployment North Korea Analog Chosatong (experimental) Palau Analog still used Turkmenistan No digital DTT announced
Several countries have adopted digital standards but not yet completed analog switch-off, including small Pacific island nations and some African countries with limited infrastructure.
Analog Switch-Off Timeline by Region
Region First DTV Analog Off Standard ───────────────────────────────────────────────────────────── USA 1998 2009 ATSC UK 1998 2012 DVB-T Germany 2002 2009 DVB-T Japan 2003 2011 ISDB-T France 2005 2012 DVB-T Australia 2001 2013 DVB-T Brazil 2006 2018 ISDB-Tb China 2008 2015 DTMB India 2012 2019 DVB-T2 South Korea 2001 2012 ATSC/DVB-T
Modern TV Features
- HDR: High Dynamic Range (HDR10 static metadata, Dolby Vision dynamic metadata, HLG for broadcast). Peak brightness 1000-4000 nits, 10-bit color depth.
- 4K/8K: Ultra-high definition at 3840x2160 (4K) or 7680x4320 (8K). Requires HEVC/VVC codec and high-bandwidth delivery (25-100 Mbps for 8K).
- HbbTV: Hybrid broadcast broadband TV — combines DVB-T/S with IP-delivered content. Supports interactive overlays, catch-up TV, and on-demand.
- HDMI 2.1: Supports 4K120Hz, 8K60Hz, eARC, ALLM, VRR for gaming.
- DVB-I: IP-based service discovery for internet-delivered TV alongside broadcast, creating a unified experience.