DVB-T2

[Laurent]

Le standard de diffusion TV numérique terrestre DVB-T a aujourd'hui dix ans et le groupement DVB a commencé de s'interroger sur l'éventualité de lui trouver un successeur (un peu à la manière du DVB-S2 qui a pris le relais du "vieux" DVB-S dans le domaine de la diffusion satellite). L'organisme a ainsi mis en place en janvier 2006 une "mission d'étude" chargée de plancher sur la question. Les membres de cette mission d'étude, qui se sont réunis pour la première fois officiellement la semaine dernière sous l'égide de Nick Wells de la BBC, ont pour tâche d'évaluer "les possibilités techniques d'amélioration des schémas de modulation pour la diffusion TV numérique terrestre". Les conclusions du groupe d'experts devraient être connues d'ici à l'automne prochain. Ce n'est qu'alors que les travaux sur un éventuel standard DVB-T2 pourraient démarrer.

A l'occasion du salon NAB 2007, qui a ouvert ses portes lundi 16 avril à Las Vegas (Etats-Unis), le Forum DVB a annoncé la publication de de... Texte : A l'occasion du salon NAB 2007, qui a ouvert ses portes lundi 16 avril à Las Vegas (Etats-Unis), le Forum DVB a annoncé la publication de deux documents liés au futur standard de diffusion numérique terrestre DVB-T2. Destiné à compléter l'actuel DVB-T, le DVB-T2 sera en particulier adapté à la diffusion de programmes TVHD en permettant d'injecter dans un canal UHF de 8MHz un débit de 30% supérieur à celui autorisé par son aîné (24Mbit/s, selon les spécifications françaises actuelles). L'un des documents détaille les besoins commerciaux (Commercial Requirements) auxquels devra répondre la norme DVB-T2, tandis que le second est un appel à propositions techniques ad hoc. Celles-ci doivent être remises au Forum DVB d'ici au début du mois de juin. Un premier projet de standard pourrait voir le jour début 2008.

Source : Electronique International


Les docs officielles : le standard DVB-T2 sur le site DVB.org:
https://www.dvb.org/standards/dvb-t2

une explication succincte: fact sheet:
https://www.dvb.org/resources/public/factsheets/dvb-t2_factsheet.pdf

une autre explication rapide, cette fois en français.
voir page 131

Report ITU-R BT.2254, Frequency and network planning aspects of DVB-T2:
https://www.itu.int/dms_pub/itu-r/opb/rep/R-REP-BT.2254-2012-PDF-E.pdf

ETSI EN 302 755 V1.4.1 (2015-07): Frame structure channel coding and modulation for a second generation digital terrestrial broadcasting system (DVB-T2)
http://www.etsi.org/deliver/etsi_en/302700_302799/302755/01.02.01_40/en_302755v010201o.pdf

ETSI TS 102 831 V1.2.1 (2012-08): Implementation guidelines for a second generation digital terrestrial television broadcasting system (DVB-T2)
http://www.etsi.org/deliver/etsi_ts/102800_102899/102831/01.02.01_60/ts_102831v010201p.pdf

calcul du débit en fonction des différents paramettres de diffusion DVB
http://www.saschateichmann.de/dvb-t-hf.html

récapitulatif des caractéristiques du DVB-T2:
http://www.tvnt.net/forum/post579882.html#p579882

une documentation sur les streams de réference proposés par la BBC, et les streams de référence:
ftp://ftp.kw.bbc.co.uk/t2refs/
https://www.dvb.org/resources/public/documents_site/dvb-t2_referencestream-documentation.pdf

d'autres fils où l'on parle de DVB-T2 sur le forum:
Toutes les chaînes la TNT passeront en Mpeg4 en 2016
les clés USB DVB-T2 pour PC
Philips DTR 3000 - TNT HD DVBT2 PVR
La chaine UHD DVB-T2 en test sur la tour Eiffel
L'expérimentation DVB-T2 à Rennes

[brebis]

Salut !

Chez vous, en France, pour fin 2008, tous les matos vidéos (TV, récepteu(rs TNT, externes, graveurs DVD) devront être compatibles TNT HD (donc, avec tuner MPEG-2 et 4)... mais à la norme DVB-T.

Or, un premier projet de standard DVB-T2 devrait voir le jour en 2008.

Alors, finalement, y a-t-il un risque de posséder fin 2008 du matos TNT HD déjà considéré comme presque obsolète car à la norme DVB-T actuelle, alors que se profile déjà tout doucement la norme DVB-T2, qui je suppose, sera INCOMPATIBLE avec la norme DVB-T "tout court" ?

Bref, un peu comme si la France décidait, même pour vos chaînes gratuites, de supprimer pour la TNT dès 2008 le MPEG-2 pour passer uniquement au MPEG-4... alors que de très nombreux adaptateurs TNT seulement MPEG-2 ont déjà été vendus depuis mars 2005 (lors du lancement de la TNT chez vous), ce qui rendrait bon nombre de vos téléspectateurs "aveugles" devant leur TV (écran noir).

Autrement dit, on veut toujours forcer les gens à consommer le plus possible (donc, à renouveler le plus rapidement possible) au lieu de garder son matos pendant un certain nombre d'années !

[Laurent]

Update on the proposed DVB-T2 specification

Approval for the DVB-T2 specification is well underway. In late February, DVB's CM-AMT, the DVB group that developed the commercial requirements for the DVB-T2 specification, assessed the proposed DVB-T2 specification. While it raised a few concerns, CM-AMT is confident that the proposed technical specification meets with its commercial requirements.

As a next step, the proposed specification will need to be approved by the DVB Technical Module and endorsed by the Commercial Module before submission to the DVB Steering Board. Provided that the process runs smoothly, it can be expected that the Steering Board will approve the DVB-T2 specification on 24 April.

Agreed baseline features

The proposed DVB-T2 specification is expected to provide a capacity gain between of 30-50% in comparison with DVB-T. While commercial requirements call for a minimum gain of 30%, some in the broadcast industry have indicated that a 30% gain may not be sufficient to warrant the launch of the new standard. The specification is designed primarily for fixed reception to roof-top antennas and has the same frequency spectrum channel characteristics as DVB-T allowing for compatibility with Geneva 2006 Agreement.

The technical group responsible for developing the DVB-T2 specification put in place a base specification consisting of a set of "safe-proven" options against which alternative and more radical options can be measured. The set of features is rather flexible and avoids the need for multiple DVB-T2 profiles.

Some of the features of DVB-T2 baseline likely to be included:
• same FEC as DVB-S2 (rates 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6)
• compatible with DVB-S2 system layer (baseband frames)
• classical Guard Interval OFDM:
- FFT sizes 1K, 2K, 4K, 8K, 16K, 32K
- Guard Intervals 1/128, 1/32, 1/16, 19/256, 1/8, 5/32, 1/4
• 7 patterns of scattered pilots including a low-overhead pattern for use with CD3 (decision feedback equalisation)
• continual pilots for common phase error rejection
• Time Slicing at the physical layer (to enable power saving)- different Physical Layer Pipes (PLPs) can have different levels of robustness
• P1 symbol for frame sync and -T2 signal detection
• P2 symbol carrying frame construction data and PSI/SI
• Interleaving at three levels:
- bit interleaving
- time interleaving
- frequency interleaving
• MISO (Multiple Input Single Output) capability based on Alamouti transmit diversity
• Future Expansion Frames
• Constellation extensions to 256QAM and hybrid constellations
• Rotated Constellations (under study for performance and complexity)

As a next step, the baseline specification will be presented at the next Technical Module meeting in March for approval.

Time Frequency Slicing

An innovative feature proposed for the DVB-T2 specification, Time Frequency Slicing (TFS) creates a large multiplex by combining radio-frequency channels to make a single 'virtual' channel to allows for efficient statistical multiplexing. While initial thought to offer a 25-50% capacity gain, this value has since been scaled down to 10-13% across four radio-frequency channels.

However, not all of the details of TFS have yet to be confirmed and some technical concerns remain (will loss of one multiplex lead to the loss of all multiplexes, will channel estimation suffer?…). Some have estimated that the full implementation of TFS into the DVB-T2 specification would have delayed the completion of the specification by up to 2 years.

Not wanting to delay the release of the DVB-T2 specification but still interested in benefiting from TFS in the future, 'hooks' have been put in the specification to allow for the introduction of TFS at a later stage. The requirement of a second tuner will be included and is currently estimated at only 4% of the total bill of materials.

Adopting the new standard

At this stage, only the communications regulator in the United Kingdom, OFCOM, has officially presented a plan that calls for the use of the DVB-T2 specification in a national DTT multiplex.

According to OFCOM, the introduction of DVB-T2 could allow for the provision of 4-5 high-definition television services from a single multiplex. By introducing such services into frequencies already allocated to broadcasters, OFCOM has sidestepped the need to further allocate frequencies in bands IV/V for broadcast services. Some doubts remain, however, with the technical assumptions made in the OFCOM proposal.

Apart from the United Kingdom, no other country in Europe has issued clear plans for the introduction of DVB-T2 services although some have indicated interest.

There are fears that countries that have not yet launched DTT services using the DVB-T standard may choose to wait until DVB-T2 products become available. Doing so, however, will lead to a delay in the launch of DTT services and postpone the switch-off analogue services for a corresponding period.

Further fears have been raised that DVB-T2 may cause significant damage to the perception of DVB in South America where decisions on which digital television standard to adopt have not yet been made. Opponents to DVB have claimed that the need for a "second version" of the terrestrial standard must demonstrate the weakness of DVB-T. However, this has been consistently countered by the continual efforts of the DVB who can point to DVB-T's track record of success over the last ten years.

DigiTAG

[reslfj]

Update on the proposed DVB-T2 specification

Provided that the process runs smoothly, it can be expected that the Steering Board will approve the DVB-T2 specification on 24 April.

Agreed baseline features

Some of the features of DVB-T2 baseline likely to be included:
• same FEC as DVB-S2 (rates 1/4, 1/3, 2/5, 1/2, 3/5, 2/3, 3/4, 4/5, 5/6)
• compatible with DVB-S2 system layer (baseband frames)
• classical Guard Interval OFDM:
- FFT sizes 1K, 2K, 4K, 8K, 16K, 32K
- Guard Intervals 1/128, 1/32, 1/16, 19/256, 1/8, 5/32, 1/4
• 7 patterns of scattered pilots including a low-overhead pattern for use with CD3 (decision feedback equalisation)
• continual pilots for common phase error rejection
• Time Slicing at the physical layer (to enable power saving)- different Physical Layer Pipes (PLPs) can have different levels of robustness
• P1 symbol for frame sync and -T2 signal detection
• P2 symbol carrying frame construction data and PSI/SI
• Interleaving at three levels:
- bit interleaving
- time interleaving
- frequency interleaving
• MISO (Multiple Input Single Output) capability based on Alamouti transmit diversity
• Future Expansion Frames
• Constellation extensions to 256QAM and hybrid constellations
• Rotated Constellations (under study for performance and complexity)

As a next step, the baseline specification will be presented at the next Technical Module meeting in March for approval.

Are there any news about the status and dates ?

This presentation RAI on DVB-T2 listed some different values and some values are missing.

• code rates 1/4, 1/3 and 2/5 are missing ?
• the guard interval 19/128 ( and not 5/32 = 20/128) ?
• 8 pilot patterns are listed - not just 7 ?

What are "hybrid constellations" ?
Are "Rotated Constellations" allowed for all OFDM modes including 256QAM ?

Is there any info like ETSI EN 300 744 Annex A :
"Simulated system performance for 8 MHz channels" ?

Lars

[jeanphi73]

La BBC teste le DVB-T2:

http://www.digitalspy.co.uk/digitaltv/a ... sions.html

[Laurent]

Le 1er décodeur DVB-T2 sera montré en fonctionnement lors de l'IBC 2008 à Amsterdam.

[Franck Morin]

Le 1er décodeur DVB-T2 sera montré en fonctionnement lors de l'IBC 2008 à Amsterdam.

Cela veut donc dire que les anglais font des tests sur de prototypes uniquement ? Ou que les tests n'ont pas encore débutés ?

[Laurent]

http://www.dtg.org.uk/news/news.php?cla ... t2&id=3030
BBC begins DVB-T2 test transmissions

The BBC has begun DVB-T2 test transmissions from the Guildford transmitter southwest of London, in preparation for HD on Freeview. The transmission facilities are provided by National Grid Wireless and Arqiva as part of their support for the DVB standardisation process and the UK project for the launch of DVB-T2 services.

This follows the approval by the DVB Project of the DVB-T2 specification and this will be the first time signals compliant with the DVB-T2 specification will be broadcast. DVB-T2 is the next generation digital terrestrial transmission standard for new HDTV services on Freeview. Currently, Freeview services use the DVB-T standard which was defined more than 10 years ago. DVB-T2 can provide significantly more capacity and this will be essential for HDTV services to be launched on Freeview, currently planned for the end of 2009.

BBC Research & Innovation has been leading the work of the DVB group. In parallel, it has been developing a modulator/demodulator ("modem") compliant with the new specification.

Justin Mitchell, leader of the DVB-T2 modem development team at the BBC, said: "We are delighted that our team in collaboration with our partners has been able to deliver such a key piece of technology in such a short timescale. This is a big step forward in enabling the introduction of full HD terrestrial on Freeview by the end of 2009."

DTG Staff | 27.06.2008

[Laurent]

Le 1er décodeur DVB-T2 sera montré en fonctionnement lors de l'IBC 2008 à Amsterdam.

Cela veut donc dire que les anglais font des tests sur de prototypes uniquement ? Ou que les tests n'ont pas encore débutés ?

Oui, ce sont des prototypes, et au moins un fabricant européen fera des démonstrations à l'IBC, probablement avec un flux enregistré.

[Laurent]

http://www.dvb.org/news_events/dvbscene ... CENE27.pdf

Le DVB-T2 est préconisé dans les pays opérant le passage au tout numérique. Le Royaume Uni devrait être le 1er à le tester. Il est préconisé de diffuser simultanément DVB-T et T2 pendant quelques temps, avant de passer intégralement au T2.
L'Ofcom, office de régulation des télécoms UK, préconise la conversion d'un multiplexe en T2, incluant des chaînes HD, fin 2009.
La BBC a commencé des tests DVB-T2 de transmission depuis l'émetteur de Guildford au sud de Londres. Les moyens de transmissions sont fournis par Arqiva et National Grid Wireless.