Introduction to SDV
Owen Lin
April 18, 2007Some information obtained from:
Scientific Atlanta – SDV Overview
BigBand Whitepapers –The Statistics of SWB
What Is SDV and What Does It Do?
• Switched Digital Video– A technology which brings multicast efficiency to digital video
distribution– Enables MSO's (Multi Service Operators) to offer a wider
variety of programming– Efficiently manages their HFC (Hybrid Fiber/Coax) network's
bandwidth.
• Allocates bandwidth to requested channels • Frees up bandwidth from services no longer in use
– Traditionally, a broadcasted channel has permanent bandwidth allocated to it
• Wasteful if nobody is watching the service.• Detailed logs of bandwidth allocation and channel viewership
Why All the Rage?
• Competitive advantage, bringing the best for the least• Reduces investment cost - scales logarithmically to programming
services, rather than linearly
• SD (Standard Definition) channel uses about 3-6Mbps• HD (High Definition) channel requires approximately 15-22Mbps,
depending on the amount of motion and frequency of scene changes.
• A 256-QAM can supply 38.8Mbps. – That translates roughly to 9 SD channels or 1, maybe 2, HD
channels.
Example of Numbers
• An MSO broadcasts a 300 channel lineup, 20 of them HD's– 280 sd * 4 Mbps % 38.8 Mbps = 29 Qams needed per node *– 20 hd * 18 Mbps % 38.8 Mbps = 10 QAMs needed per node *– 39 QAMs are required per node (200-2000 tuners, varies by MSO)
• % = modulus
• An MSO uses SDV to offer a 300 channel lineup, 20 of them HD’s– The 80/20 rule followed by tv watchers – 56 sd, 4 hd channels are being watched by 80% of the audience
• 8 QAMs required– Covering vast majority of audience, approx 100 unique streams– about 1/3 the channel bandwidth
• MSO investment in QAMs at the hub level are heavily reduced
Additional Research
• BigBand, top 5 MSO, and S-A STB test trial on SDV– 915 subscribers– 171 switched channels– 100 streams resourced (only 67 were required in hindsight)
Kagan Research
• A study conducted by Kagan Research found that at any given moment the actual number of broadcast channels being viewed within a given node was far less than the number being broadcast.
Why Switched Digital Video?Bandwidth
• SDV– Gives your site more
flexibility to deliver more of the services that consumers want today
– Allows greater bandwidth capacity because NOT every channel is delivered at the time
Switched Digital Video
Switched Channels Everyone could get
their own special channels: increased
appeal of overall package to ALL
subscribers
Broadcast Channels
Au
die
nc
e
Broadcast Channels
Current Analog & Digital Broadcast Approach Only the most
popular channels are offered due
to capacity constraintsUnused
Capacity
“The Long Tail”
Why Switched Digital Video?Summary
Traditional Broadcast Switched Digital Video
200
ProgramsOffered
20QAMs
HFCBandwidthRequired
300
ProgramsOffered
30QAMs
HFCBandwidthRequired
200
ProgramsOffered
6-8QAMs
HFCBandwidthRequired
300+
ProgramsOffered
nQAMs
HFCBandwidthRequired
Bandwidth scales as number of
offered channels Immediate bandwidth
savings
HFC bandwidth scales based on viewership
HFC bandwidth required is
independent of number of
offered channels
MSOs can save bandwidth by delivering programs based on viewership
Section:SDV
Elements
DNCS
SDV Manager
SDV Server
Mini Carousel
DCM
NetCrypt
Switches & Routers
QAMs
STB Client
Management
SDV ElementsManagement Network – Key Players
HFCNetwork
VideoContent
IP Network
ControlIP Network
QPSK
ContentSources
DNCS
DCM
SDV Server
GQAM
SDV Client(on STB)
NetCrypt
Management& Provisioning
Server Interactive Session Request
MiniCarousel
Channel Change
Message
SessionBinding
ShellSessionSetup
IGMP Join
Out-of-BandChannel
Video Sources
GroomedVideo
EncryptedMulticast
Video
In-BandChannel
SDV ElementsDNCS
• DNCS System Release (min 4.2.0.2xx)– Features enabled with separate licenses
• Session Resource Manager (SRM)– Governs access to content and network resources– Allows sharing of those resources by various applications
• SDV Manager– The user interface for control of the SDV servers and system– Provides a means for operator configuration of the service group
assignments and various settings for the SDV servers.
• NetCrypt™ Bulk Encryptor enabled• SDV enabled
DNCS
SDV Elements SDV Server
• The SDV server is part session manager in that it communicates directly with settops requesting channel changes
• It is also part resource manager — it requests that shell sessions be set up on a QAM feeding the required service group
• Reallocates unused bandwidth• Generates the Mini Carousel• The SDV also monitors
– Bandwidth– Channel Changes
SDV Server
SDV Elements Mini Carousel
• Mini Carousel– Carries information about the programs that are currently
being carried in the SDV service• Includes IP addresses of primary and back up servers
– Operates between the SDV Server and the SDV Client– Provides a method of
distributing tuning information to enhance channel change operation
Content Delivery
SDV ElementsContent Delivery Network – Key Players
HFCNetwork
VideoContent
IP Network
ControlIP Network
QPSK
ContentSources
DNCS
DCM
SDV Server
GQAM
SDV Client(on STB)
NetCrypt
Management& Provisioning
Server Interactive Session Request
MiniCarousel
Channel Change
Message
SessionBinding
ShellSessionSetup
IGMP Join
Out-of-BandChannel
Video Sources
GroomedVideo
EncryptedMulticast
Video
In-BandChannel
SDV Elements DCM / Staging Processor
• The Scientific-Atlanta staging processor is the Digital Content Manager (DCM)– Grooms and conditions signal sources– Aggregates multiple MPEG sources– Converts MPTS to SPTS– Encapsulates MPEG into IP/GbE– Outputs unicast IP or multicast IP as needed– Clamps content streams
to specified bandwidth
DCM / Staging Processor
SDV Elements NetCrypt™ Bulk Encryptor
• The Bulk Encryptor receives the IP content streams from the DCM / Staging Processor– SDV streams are treated as broadcast streams for purposes of
encryption • Generates and sources the IP multicasts for encrypted switched
streams • Also used to generate multicasts for unencrypted streams.
Bulk Encryptor
SDV Elements Switches & Routers
• All connections are passed through router(s) which support IGMP v3
Switches & Routers
SDV Elements QAM Modulators (GQAMs / Edge QAMs)
• QAMs receive MPEG information encapsulated as UDP streams* from the NetCrypt™ Bulk Encryptor
• QAMs request and terminate IP multicasts, and modulate the content as MPEG transport packets onto an RF carrier
GQAM
SDV Elements STB Client
• The STB requires a SARA (S-A resident applications) OS version that supports SDV
• Provides customer interface for switched services• Stores last known Mini-Carousel data• Registers all user activity with SDV Server
Settop with SDV Client
Section:Setup and
Signal Flow
SDV Components
Provisioning and Channel Change
Major SDV Channel-Change Scenarios
HFCNetwork
VideoContent
IP Network
ControlIP Network
QPSK
End-to-End System Solution and Integration
6.) GQAM: Session-based modulator with IP/GbE input, Issues IGMP message to “join” multicast group for SDV, and may also handle unicast VOD streams
1.) DCM / Staging Processor: Aggregates multiple MPEG sources, Clamps VBR programs to CBR, Converts MPTS to SPTS, Encapsulates MPEG into IP over GbE output, Addresses unicast IP for encrypted programs and multicast IP for unencrypted, and Performs DPI for ad insertion
2.) DNCS with SDV licenses
3) SRM: Allocates QAM resources for different applications including VOD and SDV, and Reclaims bandwidth from Servers as needed
7.) Switch/Routers: Standards-based with IGMPv3 SSM, Switches streams to appropriate GQAMs, and Maintains IGMP membership tables
Setup Flow - SDV Components
4.) NetCrypt Bulk Encryptor: IP network-attached encryption, Up to 4 Gbps, and Addresses multicast IP for distribution
DNCS
SDV Server
GQAM
SDV Client(on STB)
NetCrypt
ContentSources
DCM
8.) SDV Client: Provides customer interface for switched services, Stores last known Mini-Carousel data, and Registers all user activity with SDV Server
5.) SDV Server: Intel Server running Linux OS, Requests bandwidth and shell sessions from the SRM Manager, Binds shell sessions to multicast content, Distributes Mini-Carousel for topology, client configuration, and updated tuning information and Processes channel change requests
5) SDV Mgr: User interface in DNCS for control and configuration of the SDV Servers and service group settings
Signal FlowMajor SDV Channel-Change Scenarios
SDBProgramSelectConfirm
SDBProgramSelectRequest
DNCS“SRM”
SettopQAMSDV
Server
ServerInteractiveSessionRequests
ServerInteractiveSessionConfirms
QAM Shell Session Setups
SDBProgramSelectRequest/Confirm
Case 1. Program already to Service Group and in Mini-carousel
Case 2. Program already to QAM chassis for another Service Group
Case 3. Bandwidth available on QAM that is not member of that multicast group
Router
SDBProgramSelectConfirm
SDBProgramSelectRequest
Bind to multicast w/ bit-rate
IGMPv3 “Join”
Case 4. No bandwidth available on current QAMs. SDV server must request additional bandwidth from SRM
SDBProgramSelectRequest
IGMPv3 “Join” SDBProgramSelectConfirm
Bind to multicast w/ bit-rate
Bind to multicast w/ bit-rate