Video: DVB and HbbTV Technologies in TV Systems

As the amount of video consumed on the internet continues to grow, technologies that unify over-the-air broadcast with internet delivery. Doing this should allow a seamless mix meaning viewers can choose a service without knowing how it’s arriving at their TV, mobile device or laptop. This is the principle behind DVB-I and HbbTV.

In this webinar, Peter MacAvock and Peter Lanigan join moderator Dr. Jörn Krieger to answer questions about how DVB-I works and how the two organisations work together. To set the scene, Peter Lanigan explains what DVB-I is and where it sits within DVB’s other technologies.

Famous for the widespread technologies of DVB-T, -S and -C which underpin much of the world’s broadcasting, DVB have recently developed a broadcast-focused version of MPEG DASH called DVB-DASH on which DVB-I is built. Where there -T in DVB-T is for terrestrial broadcast and the -S in DVB-S for satellite broadcast, the -I in DVB-I stands for internet. Built upon the DVB-DASH standard DVB-I delivers services over the Internet to devices with broadband access whether that’s raw internet or over operator-managed networks. Most importantly, this isn’t just about TVs, but any device.

DVB-I aims to offer a way unify over-the-air broadcast with internet delivery. The apps used to deliver services to smartphones, tablets and desktops tend to create segregation as each provider delivers their own app. However, there is a benefit to removing the need for each broadcaster needing to maintain their app on all the many platforms. By unifying delivery, DVB-I also makes life easier for manufacturers who can deliver a single, consistent experience. Finally, it opens up a market for more general apps which deliver a TV experience without being tied to one broadcaster opening up more business models and a route to independent innovation.

‘Service Lists’ are the fundamental currency of DVB-I. Service discovery is therefore a critical aspect of DVB-I which was first defined in 2019 and updated in 2020. Service discovery is a technical, commercial and legal problem all of which are addressed in the DVB-I Service Discovery and Programmed Metadata standard which provides ways in which clients can access Service Lists and Service List Registries.

Another important aspect of delivery is targetted advertising since advertising underpins the business model of many broadcasters. DVB-TA defines targetted advertising for linear TV and is now being updated to include DVB-I. With DVB-TA, adverts are delivered to the receiver/device over IP based on various criteria and then triggered at the appropriate time as specified by the A178-1 signalling spec.

Source: DVB

Ahead of the Q&A, Peter MacAvock introduces the HbbTV organisation explaining how and why it works closely with DVB to generate specifications that drive Hybrid TV forward. Also a member organisation, HbbTV and DVB share many interests but where the DVB’s remit within broadcast is wider than the device-centric HbbTV scope, HbbTV also has a wider scope than DVB since STBs and other devices are in use outside of broadcasting, for instance in retail. Importantly, HbbTV has replaced MHP as DVB’s hybrid TV solution. DVB and HbbTV are sharing the task of making DVB-DASH content and validation tools available to their members.

The Q&A covers controlling of the quality of delivery, getting around the internet’s different reliability compared to RF. They also address scalability with reference to DVB-ABR Multicast. There’s a question on avoiding illegal channels being included in service lists which both Peters acknowledge is a conversation ‘in progress’ for which the technical means exist, but speficially how to implement them is still in discussion a lot of which surrounds ways to establish trust between the device and the service list registars.

The Q&A finishes by discussing whether telcos/ISPs are interested in adopting DVB-ABR Muilticast, compatability between DVB-I and HbbTV as well as 5G broadcast mode.

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Download the DVB-I Presentation
Download the HbbTV Presentation

Speakers

Peter MacAvock Peter MacAvock
DVB Chairman
Head of Delivery, Platforms and Services, EBU Technology and Development
Peter Lanigan Peter Lanigan
Senior Manager, Standardisation,
TP Vision
Jörn Krieger Moderator: Jörn Krieger
Freelance Journalist

Video: DVB-I. Linear Television with Internet Technologies

Outside of computers, life is rarely binary. There’s no reason for all TV to be received online, like Netflix of iPlayer, or all over-the-air by satellite or DVB-T. In fact, by using a hybrid approach, broadcasters can reach more people and deliver more services than before including securing an easier path to higher definition or next-gen pop-up TV channels.

Paul Higgs explains the work DVB have been doing to standardise a way of delivering this promise: linear TV with internet technologies. DVB-I is split into three parts:

1. Service discovery

DVB-I lays out ways to find TV services including auto-discovery and recommendations. The A177 Bluebook provides a mechanism to find IP-based TV services. Service lists bring together channels and geographic information whereas service lists registries are specified to provide a place to go to in order to discover service lists.

2. Delivery
Internet delivery isn’t a reason for low-quality video. It should be as good or better than traditional methods because, at the end of the day, viewers don’t actually care which medium was used to receive the programmes. Streaming with DVB-I is based on MPEG DASH and defined by DVB-DASH (Bluebook A168). Moreover, DVB-I services can be simulcast so they are co-timed with broadcast channels. Viewers can, therefore, switch between broadcast and internet services.

 

 

3.Presentation
Naturally, a plethora of metadata can be delivered alongside the media for use in EPGs and on-screen displays thus including logos, banners, programme guide data and content protection information.

Ian explains that this is brought together with three tools: the DVB-I reference client player which works on Android and HbbTV, DVB-DASH reference streams and a DVB-DASH validator.

Finishing up, Ian adds that network operators can take advantage of the complementary DVB Multicast ABR specification to reduce bitrate into the home. DVB-I will be expanded in 2021 and beyond to include targetted advertising, home re-distribution and delivering video in IP but over traditional over-the-air broadcast networks.

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Speaker

Paul Higgs Paul Higgs
Chairman – TM-I Working Group, DVB Project
Vice President, Video Industry Development, Huawei

Video: DASH: from on-demand to large scale live for premium services

A bumper video here with 7 short talks from VideoLAN, Will Law and Hulu among others, all exploring the state of MPEG DASH today, the latest developments and the hot topics such as low latency, ad insertion, bandwidth prediction and one red letter feature of DASH – multi-DRM.

The first 10 minutes sets the scene introducing the DASH Industry Forum (DASH IF) and explaining who takes part and what it does. Thomas Stockhammer, who is chair of the Interoperability Working Group explains that DASH IF is made of companies, headline members including Google, Ericsson, Comcast and Thomas’ employer Qualcomm who are working to promote the adoption MPEG-DASH by working to imrove the specification, advise on how to put it into practice in real life, promote interoperability, and being a liaison point for other standards bodies. The remaining talks in this video exemplify the work which is being done by the group to push the technology forward.

Meeting Live Broadcast Requirements – the latest on DASH low latency!
Akamai’s Will Law takes to the mic next to look at the continuing push to make low-latency streaming available as a mainstream option for services to use. Will Law has spoken about about low latency at Demuxed 2019 when he discussed the three main file-based to deliver low latency DASH, LHLS and LL-HLS as well as his famous ‘Chunky Monkey’ talk where he explains how CMAF, an implementation of MPEG-DASH, works in light-hearted detail.

In today’s talk, Will sets out what ‘low latency’ is and revises how CMAF allows latencies of below 10 seconds to be achieved. A lot of people focus on the duration of the chunks in reducing latency and while it’s true that it’s hard to get low latency with 10 second chunk sizes, Will puts much more emphasis on the player buffer rather than the chunk size themselves in producing a low-latency stream. This is because even when you have very small chunk sizes, choosing when to start playing (immediately or waiting for the next chunk) can be an important part of keeping the latency down between live and your playback position. A common technique to manage that latency is to slightly increase and decrease playback speed in order to manage the gap without, hopefully, without the viewer noticing.

Chunk-based streaming protocols like HLS make Adaptive Bitrate (ABR) relatively easy whereby the player monitors the download of each chunk. If the, say, 5 second chunk arrives within 0.25 seconds, it knows it could safely choose a higher-bitrate chunk next time. If, however the chunk arrives in 4.8 seconds, it can choose to the next chunk to be lower-bitrate so as to receive the chunk with more headroom. With CMAF this is not easy to do since the segments all arrive in near real-time since the transferred files represent very small sections and are sent as soon as they are created. This problem is addressed in a later talk in this talk.

To finish off, Will talks about ‘Resync Elements’ which are a way of signalling mid-chunk IDRs. These help players find all the points which they can join a stream or switch bitrate which is important when some are not at the start of chunks. For live streams these are noted in the manifest file which Will walks through on screen.

Ad Insertion in Live Content:Pre-, Mid- and Post-rolling
Whilst not always a hit with viewers, ads are important to many services in terms of generating the revenue needed to continue delivering content to viewers. In order to provide targeted ads, to ensure they are available and to ensure that there is a record of which ads were played when, the ad-serving infrastructure is complex. Hulu’s Zachary Cava walks us through the parts of the infrastructure that are defined within DASH such as exchanging information on ‘Ad Decision Parameters’ and ad metadata.

In chunked streams, ads are inserted at chunk boundaries. This presents challenges in terms of making sure that certain parameters are maintained during this swap which is given the general name of ‘Content Splice Conditioning.’ This conditioning can align the first segment aligned with the period start time, for example. Zachary lays out the three options provided for this splice conditioning before finishing his talk covering prepared content recommendations, ad metadata and tracking.

Bandwidth Prediction for Multi-bitrate Streaming at Low Latency
Next up is Comcast’s Ali C. Begen who follows on from Will Law’s talk to cover bandwidth prediction when operating at low-latency. As an example of the problem, let’s look at HTTP/1.1 which allows us to download a file before it’s finished being written. This allows us to receive a 10-second chunk as it’s being written which means we’ll receive it at the same rate the live video is being encoded. As a consequence the time each chunk takes to arrive will be the same as the real-time chunk duration (in this example, 10 seconds.) When you are dealing with already-written chunks, your download time will be dependent on your bandwidth and therefore the time can be an indicator of whether your player should increase or decrease the bitrate of the stream it’s pulling. Getting back this indicator for low-latency streams is what Ali presents in this talk.

Based on this paper Ali co-authored with Christian Timmerer, he explains a way of looking at the idle time between consecutive chunks and using a sliding window to generate a bandwidth prediction.

Implementing DASH low latency in FFmpeg
Open-source developer Jean-Baptiste Kempf who is well known for his work on VLC discusses his work writing an MPEG-DASH implementation for FFmpeg called the DASH-LL. He explains how it works and who to use it with examples. You can copy and paste the examples from the pdf of his talk.

Managing multi-DRM with DASH
The final talk, ahead of Q&A is from NAGRA discussing the use of DRM within MPEG-DASH. MPEG-DASH uses Common Encryption (CENC) which allows the DASH protocol to use more than one DRM scheme and is typically seen to allow the use of ‘FairPlay’, ‘Widevine’ and ‘PlayReady’ encryption schemes on a single stream dependent on the OS of the receiver. There is complexity in having a single server which can talk to and negotiate signing licences with multiple DRM services which is the difficulty that Lauren Piron discusses in this final talk before the Q&A led by Ericsson’s VP of international standards, Per Fröjdh.

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Speakers

Thomas Stockhammer Thomas Stockhammer
Director of Technical Standards,
Qualcomm
Will Law Will Law
Chief Architect,
Akamai
Zachary Cava Zachary Cava
Software Architect,
Hulu
Ali C. Begen Ali C. Begen
Technical Consultant, Video Architecture, Strategy and Technology group,
Comcast
Jean-Baptiste Kempf Jean-Baptiste Kempf
President & Lead VLC Developer
VideoLAN
Laurent Piron Laurent Piron
Principal Solution Architect
NAGRA
Per Fröjdh Moderator: Per Fröjdh
VP International Standards,
Ericsson

Video: Encoding and packaging for DVB-I services

There are many ways of achieving a hybrid of OTT-delivered and broadcast-delivered content, but they are not necessarily interoperable. DVB aims to solve the interoperability issue, along with the problem of service discovery with DVB-I. This specification was developed to bring linear TV over the internet up to the standard of traditional broadcast in terms of both video quality and user experience.

DVB-I supports any device with a suitable internet connection and media player, including TV sets, smartphones, tablets and media streaming devices. The medium itself can still be satellite, cable or DTT, but services are encapsulated in IP. Where both broadband and broadcast connections are available, devices can present an integrated list of services and content, combining both streamed and broadcast services.

DVB-I standard relies on three components developed separately within DVB: the low latency operation, multicast streaming and advanced service discovery. In this webinar, Rufael Mekuria from Unified Streaming focuses on low latency distributed workflow for encoding and packaging.

 

The process starts with an ABR (adaptive bit rate) encoder responsible for producing streams with multiple bit rates and clear segmentation – this allows clients to automatically choose the best video quality depending on available bandwidth. Next step is packaging where streaming manifests are added and content encryption is applied, then data is distributed through origin servers and CDNs.

Rufael explains that low latency mode is based on an enhancement to the DVB-DASH streaming specification known as DVB Bluebook A168. This incorporates the chunked transfer encoding of the MPEG CMAF (Common Media Application Format), developed to enable co-existence between the two principle flavors of adaptive bit rate streaming: HLS and DASH. Chunked transfer encoding is a compromise between segment size and encoding efficiency (shorter segments make it harder for encoders to work efficiently). The encoder splits the segments into groups of frames none of which requires a frame from a later group to enable decoding. The DASH packager then puts each group of frames into a CMAF chunk and pushes it to the CDN. DVB claims this approach can cut end-to-end stream latency from a typical 20-30 seconds down to 3-4 seconds.

The other topics covered are: encryption (exhanging key parameters using CPIX), content insertion, metadata, supplemental descriptors, TTML subitles and MPD proxy.

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Download the slides.

Speaker

Rufael Mekuria Rufael Mekuria
Head of Research & Standardization
Unified Streaming