Learn about why Mesh may not be the answer for #WebRTC and why the better approach is to centralize and mix all the media in an MCU. As well as an in-depth explanation on the benefits of using an MCU. As presented by Chad Hart at WebRTC Expo V.

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D3-4 Media Services -
Beyond the MCU
Chad Hart
WebRTC Expo V

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Image source: http://thewrestlinglifeupdate.tumblr.com/
Multi-PARTY! Video Conferencing

3. Easy & cheap approach to multi-party: Mesh
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Full Mesh
Works for a few
parties
No server cost
Lowest latency

4. Mesh does not scale for many video conferees
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Full Mesh
Clients get overloaded
Encode costs more than decode
Limited uplink bandwidth
Inconsistent performance
across participants

5. Traditional Telephony Approach: MCU
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Multipoint Control Unit (MCU)
Good at manipulating all media
Transcoding
Transizing
Transrating
Interworking
Server-side CPU intensive
Client can request different
conference mixes
Usually client friendly
Downsizing & mixing can reduce
bandwidth
Fewer client streams to process
MCU

6. Traditional MCU resource usage
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Worst-case process:
1. Each stream decoded
at the MCU
2. MCU mixes each
conferee
3. MCU encodes
individual mix for
each conferee
MCU
1
1 2
2
3
3
4
4
5
5
6
6
Ingress streams 6
Egress streams 6
MCU decodes 6
MCU encodes 6

7. Efficient MCU resource usage
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Efficient process:
1. Each stream decoded
at the MCU
2. MCU mixes each
conferee
3. MCU shares same
encoder for all
conferees
MCU
1
2
3
4
5
6
Ingress streams 6
Egress streams 6
MCU decodes 6
MCU encodes 1
1

8. Resource efficient MCU with encoder sharing
100%
80%
60%
40%
20%
0%
Encoder sharing vs. multi-encode
1 2 3 4 5 6 7 8 9 10 11 15 17 20
System CPU Utilization
Conferees
Traditional MCU Dialogic Evolved MCU
30%-50% reduction in compute resources
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9. Newer approach: SFU
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SFU
Selective Forwarding Unit
(SFU) routing
Clients send one & receive
many
Client can instruct SFU which
streams to send
High throughput
Can be lots of downlink
bandwidth
Low latency

10. Newer approach: SFU
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SFU
Selective Forwarding Unit
(SFU) routing
Clients send one & receive
many
Client can instruct SFU which
streams to send
High throughput
Can be lots of downlink
bandwidth
Low latency

11. New WebRTC approach: Simulcast
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SFU
High bitrate
Low bitrate
Selective Forwarding Unit
(SFU) with Simulcast
Clients send multiple streams
to SFU
one high-bit rate
one or more lower-bit
Client directs SFU which
streams to receive
Reduces bandwidth vs. SFU
Simulcast in WebRTC coming

12. A look at Google Hangouts with Simulcast
http://webrtchacks.com/hangout-analysis-philipp-hancke/
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13. Future Approach with VP9 – SVC?
Selective Forwarding Unit
(SFU) with SVC
Clients send layered stream to
SFU
Layers have varying bitrates –
time, size, quality
SFU directs who gets what
Coming to WebRTC eventually
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SFU
Layered bitrates: High Medium Low

14. Multi-party video summary comparison
http://networkfuel.dialogic.com/webrtc-whitepaper
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Building a compelling UX with a
MCU

16. Video UX: Traditional method
MCU
1 2
3 4
3G Device
Mixed stream 1 2
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3 4

17. Video UX: Traditional method
MCU
1 2
3 4
3G Device
Mixed stream 1 2
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Active Talker
Media Server Chooses Layout

18. Modern UX with MCU mixing, HTML5 & JavaScript
Mixed stream
App Server Client app
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Browser
MCU
1 2
3 4
HTML5 Canvas
Javascript
Application-defined UX
Layout
"Lorem ipsum dolor sit
amet, consectetur
adipisicing elit, sed do
eiusmod tempor
incididunt ut labore et
dolore magna aliqua. Ut
enim ad minim veniam,
quis nostrud
exercitation ullamco
laboris nisi ut aliquip ex
ea commodo
consequat. Duis aute
irure dolor in
reprehenderit in
voluptate velit esse
cillum dolore eu fugiat
nulla pariatur.
Excepteur sint occaecat
cupidatat non proident,
sunt in culpa qui officia
deserunt mollit anim id
est laborum."
Benefits:
Application defined UX
User specific & customizable layout
Lower client BW & CPU vs. mesh

19. What do you care more about?
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20. CPU & processing power is expensive
Client view Provider View
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21. Bandwidth is not always ubiquitous or free
Client-side Server-side
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22. Why do you need a media server?
Multi-party conferencing Transcoding Interworking
Recording Stream processing Person-to-machine
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23. Case Study: Video Recording Service
Key Functions
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Application highlights
Record live events – E.g. Kids
soccer game
Share event recording with
family/friends – Multi-party
stream
Supported Recording
Formats
.3GP
.mp4
.wav
Codecs
G.711, Opus, AMR-NB and
AMR-WB (voice)
VP8, H.264 (video)
Message Storage
Local storage
Remote message deposit via
MSRP
HTTP/
MSRP
REST (HTTP)
Application Server
Media Server
Message Storage
RTP (media)
Solution Highlights
Software-based Media Server
Virtualized (VM) and COTS deployment
High Availability and Geographical Redundancy
Scalability via Media Resource Broker
Architected to support 3.5M Subscriber Network
Recording
Remote Message
Deposit
Transcoding
WebRTC Signaling
WAN

24. The future: gesture controls
https://github.com/mtschirs/js-objectdetect/
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25. The future: machine vision
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26. The future: augmented reality
http://jooink.blogspot.com/2012/10/gwt-augmented-reality-howto-step-1.html
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