Webcast Technical Overview

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Context and challenges

For a few years organizations have embarked, each sector of activity having its own pace, in a digital  transformation.
Communication, internal as well as external, has not been spared by this change and this has led those organizations to increase their use of technologies.
Whether for regular communication to small audience or event-oriented massive communication to broad audiences, organizations want to simplify, make reliable and systematize the use of these technologies.
This document provides some methods to guarantee the user experience as well as reduce the impact on the organization's network.

 

Global Architecture

Client/server Architecture

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The webcast application frontend

The webcast application web page requiere media content (live or vod video and/or audio) and other basic (non media) content as synchronized slides for example.

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Only the media content presents an issue in terms of dissemination on the network of the organization:

  • Because it represents, by far, the biggest part of the total weight to be loaded by the environment of the user
  • Because it's synchronous content
  • Because an interruption in its loading can lead to a break in the playback of the media

Impact on networks

Overview of the impact

From outside the corporate network the user connects directly to the distribution infrastructure.
This is called the CDN delivery infrastructure (for Content Delivery Network)
Each user must establish a connection with the broadcast infrastructure. We are talking about broadcast infrastructure rather than server because it is often made up of a multitude of servers for reasons of reliability and performance.

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The data streams consumed by users are of two types:

  • Web page: Low data volume, asynchronous transmission
  • Video stream: Larger bitrate (eg 500kbps), continuous transmission.

If users are distributed and connected, for example through residential links, the issues for everyone are:

  • To have enough bandwidth to consume the video stream (the loading of the web page being negligible)
  • If a user does not have enough bandwidth it does not impact other users.

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If the users (or part of them) are connected from a corporate network, the stakes are different:

  • To have enough bandwidth for all users
  • If this bandwidth is not enough it's all the users who will be impacted

In certain cases it is therefore necessary to optimize the video distribution within the network.
Several methods and technologies are possible and their common concept is to relay the video stream from inside the network.

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The architecture thus created is very similar to the CDN but adapted to the corporate network. The industry calls this eCDN (for Enterprise Content Delivery Network).
Digicast deploy eCDN infrastructure in many different corporate network environments.

Relative weight of elements as a function of viewing time

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The relative weight of the page and slides is negligible compared to the video stream.
The impact calculation can almost ignore "non-video" streams.

Bandwidth

The implementation of an eCDN device is not always necessary.
The calculation of the bandwidth needed is quite simple:
𝐡𝑑 Total needed bandwidth
𝐷 Media stream bitrate
π‘ˆπ‘šπ‘Žπ‘₯ Maximum simultaneous users
𝑂 Network protocol overhead (15%-18%)

𝐡𝑑=π‘ˆπ‘šπ‘Žπ‘₯ ×𝐷 ×𝑂

If the organizer wants to reach 500 simultaneous users, taking an average bitrate of 375 kbps then the bandwidth needed is 500Γ—375Γ—1.15=216 𝑀𝑏𝑝𝑠.

 

Media Bitrates

Depending on the type of content to encode we apply the following profiles:

    Stream Sets
Streams   Audio MQ HQ HD Full HD
Audio Bitrate 128 kbps 128 kbps 128 kbps 128 kbps 128 kbps
Sampling 44.1 kHz 44.1 kHz 44.1 kHz 44.1 kHz 44.1 kHz
V1 Bitrate 60 kbps 547 kbps 1237 kbps 1519 kbps 4346 kbps
Resolution 106x60 768x432 1024x576 1280x720 1920x1080
V2 Bitrate   243 kbps 696 kbps 547 kbps 1931 kbps
Resolution   512x288 768x432 768x432 1280x720
V3 Bitrate   61 kbps 483 kbps 243 kbps 547 kbps
Resolution   256x144 640x360 512x288 768x432

 

Video rates are mainly based on a factor: the type of content to be broadcast.
The flow calculation is done thanks to 6 variables:

  • Number of lines (in pixels 𝐻𝑅𝑒𝑠)
  • Number of columns (in pixelsπ‘Šπ‘…π‘’π‘ )
  • Refresh rate (in frames per second, fps, πΉπ‘Ÿπ‘’π‘ž)
  • Bit rate per pixel (bits / px 𝐷𝑝π‘₯) - function of the complexity of the image to be encodedNumber of audio channels (π‘π‘πΆβ„Žπ‘Žπ‘›)
  • Audio bitrate (kbps,π·π‘Žπ‘’π‘‘π‘–π‘œ)


Total bitrate is the sum of audio and video bit rates

𝐷=(π»π‘Ÿπ‘’π‘ Γ—π‘Šπ‘Ÿπ‘’π‘ Γ—πΉπ‘Ÿπ‘’π‘žΓ—π·π‘π‘₯)+π·π‘Žπ‘’π‘‘π‘–π‘œ

Hosting overview

Platform details

For application hosting Digicast uses Amazon Web Services. AWS is ISO 27001 certified.
Each of the two services (Icastpro application and Media Streaming) are hosted with a geographically redundant infrastructure.

Technical architecture

The application platform consists of four components:

  • S3 block storage replicated two datacenters
  • Compute instances with automatic scaling in four datacenters
  • Load balancer to manage the instances load
  • Relational Database replicated on four datacenters with daily data snapshots

The media streaming infrastructure consists of two media origins located in two different datacenters.
Each Origin is feeding a network of 82 edge servers location for distribution. A smart media player is getting the stream from one of the edge location depending on the health of each.

 

IPs and Domains

⚠ To serve large audiences, icastPro relies on a geographically distributed infrastructure to deliver content to attendees at the best possible quality. This "Content Delivery Network" (or "CDN") consists of thousands of edge nodes all over the world.

As such, we cannot provide a list persistent IP addresses for our services as they change frequently depending on size and location of the audience. We reccommend that you avoid using IP-based firewall rules and instead use our domains.

However we do provide IPs for virtual meeting room speaker access here.

To whitelist our participant-side services you can use the following subdomains:

Subdomain

 Content Data type Service

*.icastpro.ca

www.icastpro.ca

 Web app Text/images Load Balancer
assets.icastpro.ca Static JS, CSS Imges, fonts Text/images CDN

cdnp.icastpro.ca

cdn-p.icastpro.ca

cdn*.icastpro.ca

 HLS Audio /Video streams CDN

cdnb.icastpro.ca

cdn-b.icastpro.ca

cdn*.icastpro.ca

 HLS Audio /Video streams CDN
*.icastcdn.net HLS Audio /Video streams CDN
content.icastpro.ca Non-video content (slides, documents) Slides CDN
timings.icastpro.ca Slides index (every 3 to 5 seconds) Text CDN
forms.digicast.ca Advanced registration  forms Text/images Web server
auth.digicast.ca Authentication / SSO Text Web server
support.icastpro.ca Participant support application Page Zendesk

 

Note: The system can also send email notifications via notifications@icastpro.ca
Our automatic email sending systems are compatible with DKIM and SPF.

 

Geography

Digicast is using two location in North America:

  • North Virginia (with four availability zones)
  • Center Canada (with two availability zones)

The Amazon CloudFront Global Edge Network

To deliver content to end users with lower latency, Amazon CloudFront uses a global network of edge locations for content delivery. Amazon CloudFront edge locations are located in:

North America

United States

Edge Locations
● Ashburn, VA (3)
● Atlanta, GA (2)
● Chicago, IL
● Dallas/Fort Worth, TX (2)
● Hayward, CA
● Jacksonville, FL
● Los Angeles, CA (2)
● Miami, FL
● Minneapolis, MN
● New York, NY (3)
● Newark, NJ
● Palo Alto, CA
● Philadelphia, PA
● San Jose, CA
● Seattle, WA
● South Bend, IN
● St. Louis, MO
Regional Edge Caches
● Northern Virginia
● Oregon

Canada

Edge Locations
● Montreal, QC
● Toronto, ON

South America

Edge Locations
● SΓ£o Paulo, Brazil (2)
● Rio de Janeiro, Brazil
Regional Edge Caches
● SΓ£o Paulo, Brazil

Europe

Edge Locations
● Amsterdam, The Netherlands (2)
● Berlin, Germany
● Dublin, Ireland
● Frankfurt, Germany (5)
● London, England (4)
● Madrid, Spain
● Marseille, France
● Milan, Italy
● Munich, Germany
● Paris, France (2)
● Prague, Czech Republic
● Stockholm, Sweden
● Vienna, Austria
● Warsaw, Poland
● Zurich, Switzerland
Regional Edge Caches
● Frankfurt, Germany

Asia

Edge Locations
● Chennai, India
● Hong Kong, China (3)
● Mumbai, India (2)
● Manila, the Philippines
● New Delhi, India
● Osaka, Japan
● Seoul, Korea (3)
● Singapore (2)
● Taipei, Taiwan
● Tokyo, Japan (3)
Regional Edge Caches
● Mumbai, India
● Singapore
● Sydney, Australia
● Seoul, South Korea
● Tokyo, Japan

Australia

Edge Locations
● Melbourne, Australia
● Sydney, Australia
Regional Edge Caches
● Sydney, Australia

 

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