Transcript IP Connectivity

Broadcast Day SSPI - 2007
Carlos Capellão
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Linha de Produtos PHASE
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IP as Connectivity – Is IP Replacing ASI?
Introduction
• We will discuss ASI versus IP for digital video
connectivity.
• For IP, we will really concentrate on Gigabit
Ethernet.
• We will discuss:
–
–
–
–
Physical layer implementation
Timing features
Packet loss issues
Routing of traffic
• And we will conclude that IP is a good
replacement for ASI!
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ASI Versus Gigabit Ethernet Physical
Parameter
ASI
Gigabit Ethernet
Line Bit Rate
270 Mb/s
1.25 Gb/s
Line Coding
8B/10B (based on
Fiber Channel)
8B/10B (based on
Fiber Channel)
Information Bit
Rate
216 Mb/s
1.0 Gb/s
Link Type
Unidirectional
point-to-point
Dual-Unidirectional
point-to-point
When to transmit?
Whenever I want
Whenever I want
Byte
Synchronization
Sends sync pattern
when idle
Silence when idle,
8-byte sync before
packet
Frame check
None (ReedSolomon optional)
CRC
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Physical Layer Notes
• Gigabit Ethernet is always switched
– No contention
– Always full-duplex
• ASI interfaces typically transmit at a constant bit
rate, hardware-metered
• ASI interfaces are unidirectional
• Gigabit Ethernet interfaces are always composed
of two unidirectional interfaces, one on each
direction
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Timing Recovery
ASI
Transport
Packets
Buffer
Modulation
RF
Clock
Clock
Time stamps Recovery
Buffer Fullness
More Complex
Larger Buffer Required
Algorithm
Buffer
Ethernet
Transport
Packets
Modulation
Clock
Time stamps Recovery
Buffer Fullness
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Clock
RF
Decoder Playback Process (ASI)
Buffer
Level
Decoder starts playing
VBV
Time
I
B
B
P
B
T=0, decoder
starts receiving data
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B
P
B
B
P
B
B
P
Decoder Playback Process (Ethernet)
Buffer
Level
Decoder starts playing
VBV
Time
I
T=0, decoder
starts receiving data
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B
B
P
B
Packet Reception Times
9
B
P
B
B
P
B
B
P
Conclusions so far…
• From a physical layer point of view, ASI and
Ethernet are very similar
– Point-to-point packet transport mechanism
• Ethernet always has a CRC so bit errors can be
detected
– With ASI, even if configured for 204-byte mode (ReedSolomon), the great majority of the equipment does not
generate or check it – that is done by modulators and
demodulators.
• Differences in packet timing are very manageable
• But … what about packet loss???
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The Packet Loss “Issue”
• Let’s look first at a point-to-point connection with
a crossover cable.
• There is no contention, no buffering – it is almost
the same as having two ASI connections, one in
each direction.
• The only way a packet can be dropped is if the
receiver drops it – and that is not going to
happen (by design)!
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Ethernet Switches
Ethernet
Port
Ethernet
Port
Ethernet
Port
Non-Blocking
Switch
Fabric
Ethernet
Port
• All modern switches are non-blocking and can
operate at line rate.
• Transmit and receive channels are independent.
• Switches also have a certain amount of buffering.
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Where is the Packet Loss, then?
Data 6 Mb/s
Source
Switch
Link Capacity: 10 Mb/s
Data
Source 6 Mb/s
2 Mb/s Packet Loss
• Packet loss happens when a link is
oversubscribed – more traffic than its capacity.
• Switch will buffer instantaneous bursts, but
cannot buffer forever.
• Solution: don’t do it!!
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Packet Loss Notes
• Packet loss happens when there is congestion in
the network.
• Short-term congestion introduces jitter (as
packets are buffered); long-term congestion
introduces packet loss.
• Congestion is avoided by properly designing the
network capacity for the traffic.
• Good news is that, unlike data, digital video
capacity requirements are well-known and easy
to design for.
• If you want to mix video and data in the same
network, high-end routers and switches can be
configured to give priority to video.
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Dealing with Occasional Packet Loss
• Occasional packet loss, for whatever reason, can
be handled by FEC.
– Slightly different from the traditional FEC – we rebuild
“lost” bits instead of “correcting” wrong bits.
• Standardized FEC options:
– RFC 2733: “Row” FEC.
– Pro-MPEG FEC: “Column” and “Row” FEC, can handle
burst losses.
• FEC is supported in most Tandberg equipment
and interoperates with equivalent
implementations from third-party vendors
– Interop demonstrated in VSF meeting in Orlando last
January.
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IP Advantages over ASI
• We have seen that, from a transport point of
view, IP and ASI are fairly equivalent, with a
small advantage in favor of IP (FEC).
• As a system interconnect solution, IP has two
major advantages over ASI:
– IP has a network layer: IP packets contain routing
information, indicating where they should go. That
includes IP multicast – one-to-many delivery.
– IP equipment is universal, and there are many vendors
to choose from – high volume items, very costeffective.
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ASI Interconnect
Video
Source
Video
Source
ASI
ASI
ASI
Switch
ASI
Modulator
Decoder
ASI
Modulator
Decoder
ASI
Modulator
Decoder
$$$$$
Video
Source
ASI
Control
Terminal
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Required since
Transport packets do
not carry addresses
IP Interconnect
Ethernet Modulator
Decoder
Video Ethernet
Source
Video Ethernet
Source
Ethernet
Switch
Ethernet Modulator
Decoder
cheap
Ethernet Modulator
Decoder
Video Ethernet
Source
Control is not
required since each
packet contains an
address!!
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IP Technology – Bits and Pieces
Ingress: Encoders
EN Series
iPlex
Mediaplex
• All Tandberg Encoders either have IP output built
in (iPlex, Mediaplex) or offered as an option (EN
series)
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Encoders at a Glance
• EN Series (single channel) SDTV/HDTV – MPEG2/MPEG4
–
–
–
–
–
–
–
–
–
EN5710/5720: MPEG-2 Standard Definition
EN5770/5775: MPEG-2 Standard Definition Dual-Pass
EN5780/5782: MPEG-2 High Definition
EN5920: Windows Media/VC-1 Standard Definition
EN5930: H.264 Standard Definition
EN5980: Windows Media/VC-1 High Definition
EN5990: H.264 High Definition
EN8030: Second Generation H.264 Standard Definition
EN8090: Second Generation H.264 High Definition
• Mediaplex, iPlex (multiple channel)
– MPEG-2 Standard Definition Submodule (up to 48 in the
Mediaplex, up to 8 in the iPlex)
– H.264 Standard Definition (up to 48 in the Mediaplex, up to 8
in the iPlex)
– H.264 Second Generation Standard Definition (up to 4 in the
iPlex, Mediaplex support planned).
– H.264 High Definition (up to 4 in the iPlex, Mediaplex support
planned)
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Network Interfaces and Protocols
• Interfaces:
– EN Series:
• Dual copper Gigabit Ethernet Interfaces
– iPlex:
• Dual Gigabit Ethernet (SFP – fiber and copper available)
– Mediaplex
• Four Gigabit Ethernet Interfaces (multimode fiber)
– Mediaplex/iPlex also support optional ATM OC-3, DS-3
and E-3 interfaces.
• Protocols:
– UDP
– RTP
– Forward Error Correction
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Receivers at a Glance
TT1260: MPEG-2 SD 4:2:2
TT1222: MPEG-2 SD 4:2:0
TT1280/2: MPEG-2 HD
RX1290: Everything
• All Tandberg Receivers include a Professional Decoder
• Receivers have a variety of available input front-ends
(including IP), optional descrambler, and an ASI output
• The TT1222 includes an IP output option.
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Process: Multiplexers and Demultiplexers
Mediaplex
iPlex
MX8400
• Capable of multiplexing
and demultiplexing IP
flows.
• Extensive set of (P)SI
table generation options
• Functions also available
on ASI.
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• High-end
multiplexer, GE
inputs and outputs
• Scrambling also
available
Process: Rate Shaping
• Rate Shaping: Converting a service
from one bit rate to another
– To fit in a bandwidth-limited channel
– Convert to CBR for video servers
• Function provided by the Media
Processor submodule in
iPlex/Mediaplex
Mediaplex
– Mediaplex: support for approximately
144 services.
– iPlex: support for approximately 36
services.
– Actual number depends on bit rate
• Inputs and outputs can be IP
streams
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iPlex
Process: MPEG-2 to H.264 Conversion
• Most existing content from
broadcasters comes in as MPEG-2.
• In some installations, it may be
desirable to convert it to H.264.
• The Media Processor submodule in
the iPlex/Mediaplex can provide this
function.
• Capacity:
Mediaplex
– Mediaplex: 48 services
– iPlex: 8 services
• Inputs and outputs can be IP
streams.
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iPlex
Conclusions
• There are devices available for the entire digital
video processing chain that can use an IP
network as the interconnection method.
• This IP interconnect can be restricted to the
head-end or can extend all the way to the
consumer set-top box.
• IP interconnects can be used in traditional digital
video architectures (digital cable, satellite) inside
the head-end, while maintaining the same egress
method.
• Tandberg Television has all the “bits and pieces”
required to make this work!
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Obrigado!
Carlos Capellão
[email protected]
Tel. 21.2493.0125
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