OTT and IPTV

Over-the-Top (OTT) and Internet Protocol Television (IPTV)

Over-the-Top (OTT) are also called internet TV.

A general definition of OTT and IPTV is video television content that, instead of being delivered through traditional broadcast and cable formats, is received by the viewer through the technologies used for computer networks.

Key Benefits of OTT and IPTV

End-users: personalization of services; subscribers can choose what to view and when to view.
Service providers: conserve the bandwidth used as the content is broadcasted only on the demand of the end-user based in the network.
Not only on TV but we can also watch them on desktop, laptop, mobiles, and tablets, etc.
Support features like music on-demand, pause TV, fast- forward TV, re-play TV, weather information and multimedia player, etc.
Advertising can also be done through IPTV, as Ad insertion is done in many videos we watch online and we can’t skip them completely, and we have to watch some part of it.

The Layered Architecture for OTT and IPTV

Data Transport layers is replaced by Containers
Does not need Modulation

Internet Protocol television (IPTV) vs OTT

Both are not delivered through traditional broadcasting networks

video over the Internet

IPTV is fundamentally different from OTT.

IPTV (telco TV): uses closed and controlled by an operator or telecom service provider
- E.g. Now TV, use the PCCW network
OTT: uses open internet, un-managed network, open ecosystem, exactly like the Web.
- E.g. Netflix, MyTVSuper

A Quick summary:

OTT even has user generated content, thus its program are only limited by imagination.

IPTV

Conventional TV content distribution uses satellite, cable and terrestrial broadcast system formats.

But in IPTV:

the broadcast of the television series by using the Internet via Internet Protocol (IP) networks.

IPTV is very popular nowadays because of its features that allow the subscribers to watch not only the TV shows on their favorite channels but also live broadcasts of their favorite shows, movies, live games like cricket, football, etc and even watching backdated shows of one’s favorite programs.

Multicast in IPTV networks

Multicast: the sender transmits content once regardless of the number of receivers.
Multicasting over point-to-point networks (e.g. wired Internet or IPTV) is more complex
- it requires additional protocol-level support to construct a multicast distribution tree spanning the sender (source) and the receivers (destinations).

Unicast: a form of network communication where the stream is sent multiple times directly to each receiver

the sender transmits the same content N times for N receivers in the absence of multicast technology, resulting in a significant load over the network infrastructure.

Multicast: a stream that is sent once but can be received by multiple receivers

the sender sends the content once for all receivers and the network replicates content only as many times is necessary to reach the final destinations.

Types of IPTV

Live Television

Live broadcast of television or live streaming videos/audio/games etc. with minimum latency
- multicast is used in order to save the bandwidth

Time-shifted television or Digital Video Recorder (DVR)

permits to watch TV shows that were originally broadcasted some hours before or some days before and replay of current ongoing shows. The users can view their favorite shows later and even if they miss the broadcast of them due to lack of time at the time of telecast on TV.
- Unicast is used, since point-to-point connection is needed

Video on Demand (VOD)

Each user will have a collection of different media files that are stored in his/her device and one can browse and watch them anytime just by selecting them.
- This feature of Internet Protocol TV uses the real-time streaming protocol for transmission as it deploys unicast mode of transmission. (since point-to-point connection is needed)

IPTV

IPTV carries both the video on demand (VOD) service which is a unicast and live TV which is multicast service.

Left side : Live TV

Right side : VOD

For residential users, IPTV is often provided in conjunction with Video on Demand and may be bundled with Internet services such as Web access and VoIP. The commercial bundling of IPTV, VoIP and Internet access is referred to as “Triple Play” service.

Transcoding

Decode and then Encode again
Used to support different user at different bit rate and resolution

DSL (Digital Subscriber)

DSL: Digital Subscriber Line. Users get a high speed bandwidth connection from a phone wall jack on an existing telephone network.

Push Vs Pull Systems

IPTV is a Push system
- will become less popular
- expensive to transmit, because it push the contents to all users but not all users are watching
OTT is a Pull system
- will become more popular
- only when requested by consumer

OTT

An OTT device is NOT a passive receiver that continuously receives every available video stream available to it. It must request a stream in order to receive it. This means that unicast is the dominant delivery method, which brings certain benefits such as personalized video services, but which also means the centralized video platforms must work well with network and caching infrastructure to deliver video at low latency.

Packet Loss in OTT

Video files and/or streams are broken down into small packets that form the unit of transportation.
These packets are independently routed over the network through a series of routers towards the destination.
- The intermediate routers have finite buffer size. When the traffic flowing into the buffer exceeds the traffic flowing out of the buffer, packets are dropped in the network.

Packet loss produce spatial and temporal error propagation
- Loss of packets degrades the quality of experience

Possible Solution to packet loss

feedback to the server about the quality of video they are receiving.
- Specifically, the clients inform servers about the packet loss rate
- video servers slow down injection of packets in the network if the error rate exceeds a threshold

the number of packets contending for buffer space in the intermediate routers also reduces resulting in lower packet loss.
- The number of packets in the intermediate routers ↓ => lower packet loss.
Either Reduce frame rate or Increase the quantitation step size
- both actions decrease the quality of video
- reduce the number of frames =>bitrate ↓
- the quantization step size ↑ =>bitrate ↓
This solution can only reduce packet loss, but can not eliminate all the packet loss
- there is no guarantee that packet loss will be eliminated but it does guarantee that packet loss will be reduced.

Jitter in OTT

Video: the frames/packets are generated at regular intervals
- they need to be played out at exactly the same interval in which they are generated.

Jitter in the network leads to uneven separation in playout time between two consecutive frames and that leads to degradation of quality of experience.

Possible Solution to Jitter

A buffer at the client
- holds packets for some time after their arrival at the client, before playing them out.
- briefly delaying the play out, jitter introduced in the network can be absorbed

Content Delivery Network (CDN)

Geographical distance is the biggest cause of slow content delivery.

End-to-end delay:

Propagation delay
- the physical distance divided by the speed of light.
Transmission delay
- the time needed for physical transmission of bits over a transmission line depends on the speed (bandwidth) of the transmission line.
Queuing delay
- the packets traverse several networks from the server and route to the client are queued at the intermediate routers from time to time. The more the number of networks and routers the packets have to traverse, the higher is the probability of longer queuing delay.

Due to the increase in geographical distance

Jitter: the likelihood of jitter being greater increases as the packets traverse more networks and routers from the server and route to the client.
Packet loss: If the packets traverse many networks and routers, likelihood of packet loss increases and recovering the lost packets by retransmission mechanism does not work

From a content provider’s perspective, such deterioration of quality of experience for its potential customers is not acceptable.

So Service provider has come up with Content Delivery Network (CDN).

CDN service providers create a number of mirror servers that are strategically deployed in the Internet.
Mirror servers sitting on top of the Internet leverage the network-level service of the Internet.
Mirror servers are placed in the data centers of the Internet service providers (ISPs).
CDN is considered as large number of mirror servers distributed over the Internet.
Objectives of having geographically distributed mirror servers
- serve the clients from the “nearest” mirror server in order to mitigate the effects of end- to-end delay => packet loss and jitter ↓
- The overall user experience is thus significantly improved

How CDN works

Step 0: Push all image/video files to the mirror servers

Step 1: Request index.html file from someserver.com

Step 2: Respond with index.html in which the links to image/video files are replaces with symbolic links.

Step 3: Contact the “Intelligent DNS server” to resolve the server name cdnmirror01.net into the IP address of the “closest” mirror server

Step 4: Retrieve the image/video files from the “closest” mirror server.

Challenges for CDN: how to find the “nearest” mirror server corresponding to a client?
- Typically, the IP address of the client is used to identify the location of the client. Once the location of the client is found, finding the location of the “nearest” mirror server is relatively straightforward. The exact algorithm used by different CDN service providers to find the nearest mirror server for a client is proprietary.

Hosting versus CDN

CDNs provide several advantages over hosting:
- Content distribution networks avoid bottleneck links
- Higher availability (even ISP link is dead, Mirror server can also provide the content)

OTT Ecosystem

Content Processing and Storage

Ingest & Content Management
- supports content monetization as well as the user experience of content search and discovery.
Metadata management
- helps create a personalized viewing experience that is enabled by unicast delivery.
Customer management
- authentication, preference- capture and billing processes.
Digital Rights Management (DRM)
- ensures content is only delivered to devices in permitted geographical locations that comply with the content rights.
Dynamic Ad Insertion (DAI)
- can be applied at different points in the ecosystem to insert specific advertising for the individual viewer.
Live Encode
- encode video content (a live stream or a file) for OTT delivery, adaptive bit-rates are now popular than constant bit-rates so that streams can be sustained even in networks with highly variable performance.
Packager & Origin
- wraps the video stream in the correct container to be received by different end devices (Apple, Android or Microsoft OSs)
Storage
- can be as simple as direct-attached drives, but for larger content libraries the storage is often a multi-petabyte storage system that is routinely ingesting, streaming and recording streams and files.
- An additional form of storage is the Shield Cache which provides protection to the Origin by storing the streamed content and managing the interfaces either to the CDN(s) or to the end consumer devices.

Networking

Intermediate Caching is routinely found in large networks that connect to multiple Edge Cache locations, storing popular video as close as possible to the consumer and offloading traffic from the networks that connect the Intermediate Cache with the Shield Cache or Origin. Edge Caches perform the same function – they store content as close as possible to the end consumer and avoid consuming upstream bandwidth towards the Origin which can add cost and latency.

ISP: will carry the content for the “last mile”. Generally, this means more than the last mile of course, but the key point is that network operators that provide internet services are key partners in the OTT ecosystem.

End consumer domain

In the consumer device arena, one of the main challenges for OTT Operators is the need to work with their client-side ecosystem to ensure compatibility and performance for the viewer.

Quality of Experience and Quality of Service

Quality of Experience (QoE)

monitoring and control: performed at the client-side for OTT Operators.

Quality of Service (QoS)

monitoring and control is managed at the server-side of the Ecosystem.

Key performance indicators (KPI) like average bit-rate and rebuffering ratio can be observed on every individual device and automated decisions can be taken to improve performance if necessary, such as re-directing the device to a different CDN or even Origin.
Correlation of client-side and server-side data supports proactive decisions for seamless viewing experiences.

Content Monetization: there are important monetization opportunities for OTT Operators that an internet-based content service enables. A short click to online shopping, betting, and community-based activities can be an integral part of the viewing experience, consumers and operators.

Future of OTT

OTT gives unprecedented opportunity for personalized content delivery, which transforms the relationship between consumers and content providers and enables new methods of monetization. Naturally this will lead to continued technology and business innovation.

The video processing and management technologies described in the OTT Ecosystem will therefore evolve to meet this demand.

Production side: innovate to deliver new and exciting consumer experiences
Distribution side: deal with the ever-present need to deliver content with efficiency, speed and quality.