Safe video contribution distribution over ip networks
This presentation is the property of its rightful owner.
Sponsored Links
1 / 19

Safe Video Contribution & Distribution over IP Networks PowerPoint PPT Presentation


  • 95 Views
  • Uploaded on
  • Presentation posted in: General

Safe Video Contribution & Distribution over IP Networks. Philippe LEMONNIER. High bandwidth IP networks bring new opportunities for transport of audiovisual contents. IETF has defined a basic set of RFCs so as to standardize Video transport over IP. Compressed realtime Video over IP.

Download Presentation

Safe Video Contribution & Distribution over IP Networks

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


Safe video contribution distribution over ip networks

Safe Video Contribution & Distribution over IP Networks

Philippe LEMONNIER


Compressed realtime video over ip

High bandwidth IP networks bring new opportunities for transport of audiovisual contents.

IETF has defined a basic set of RFCs so as to standardize Video transport over IP.

Compressed realtime Video over IP

Application

Network Process to Application

MPEG2 A/V

Presentation

Data Representation & Encryption

MPEG2-TS

Host layers

Session

Interhost Communication

RFC2250

RTP (RFC1889)

Transport

End-to-End Connection Reliability

IGMP

(RFC2236)

UDP (RFC768)

Network

Path Determination/Logical Addressing

IP (RFC791)

Data Link

MAC & LLC (physical addressing)

Media layers

Physical

Media, signal & Binary Transmission

MPEG compressed A/V contents mapped over IP with the IETF toolbox

OSI model


Mpeg ts mapping over ip ethernet

RTP encapsulation (optional)

12 bytes

RTP header

MPEG-TS payload

8 bytes

UDP encapsulation

UDP header

RTP header

MPEG-TS payload

20 bytes

IP encapsulation

IP header

UDP header

RTP header

MPEG-TS payload

14 bytes

Mapping over Ethernet

4 bytes

Ethernet header

IP header

UDP header

RTP header

MPEG-TS payload

Ethernet CRC

IEEE802.3 Ethernet MTU (Max. Transfer Unit) of 1500 bytes✳, restricts the blocking factor (number of grouped TS packets) to 7.

✳Jumbo frames with bigger MTU exist, but would lead to IP fragmentation in the networks.

MPEG-TS mapping over IP & Ethernet

MPEG Transport Stream packets

188 bytes

188 bytes

188 bytes


Ip networks main drawbacks

Time transparency

IP packet delay variation (IPDV) in the network is very high :

50ms as per ITU-T Rec. Y.1541, for Service Class 0 and 1 networks

… to put in perspective of 3ms ATM Cell Delay Variation around the globe, as per ITU-T Rec. I.356.

Information transparency

Technologies used for IP transport (OSI level 2) don’t lose bits :

they drop full frames (eg. up to ~1500 bytes chunks for Ethernet)

Up to 7 MPEG-TS packets can be lost at once.

The impact of an IP datagram loss is getting even worse as compression ratios rise (MPEG4…)

IP networks main drawbacks


Origin of network errors

At OSI levels 1 and 2

Bits may get twisted for electrical reasons (impulse noise, crosstalk, etc) during their trip along cable runs.

IP header processing principle in all hosts relies on header coherency.

Therefore, all technologies used to carry IP datagrams use some form of signature to ensure that the received frames carry datagrams that are safe to pass to IP level.

Dubious frames are silently discarded upon reception.

At OSI levels 2 and 3

IP networks are heterogeneous by nature. Hopping across network segments implies crossing switches (level 2) and routers (level 3).

Poor traffic engineering, network misuse or equipment problems can lead to congestion in these nodes.

Router / switch policy when facing congestion will lead to frames drop.

Origin of network errors

Medium impairment

Bridge / Router

Bridge / Router

No

Payload burst

CRC OK ?

Port 1 (in)

Port 1 (in)

Port 3 (out)

FIFO

Payload burst

FIFO

Yes

Received frame

FIFO is full

Incoming data dropped

Proceed to MAC, and upper to IP

Port 2 (in)

Port 2 (in)


Pro mpeg forum wan group

Objectives

Provide a forum for manufacturers, end-users and service providers to co-operatively develop interoperable systems for real-time delivery of high-quality program material over Wide Area Networks

Outcome

Code Of Practice #3r2✳ (July ’04)

professional MPEG-2 Transport Streams over IP networks

contribution and primary distribution applications

Addresses:

Encapsulation Protocol

Network Requirement

Pro-MPEG Forum WAN Group

✳http://www.pro-mpeg.org/publications/pdf/Vid-on-IP-CoP3-r2.pdf


Pro mpeg forum fec scheme

Pro-MPEG Forum FEC scheme

  • Based on Generic Forward Error Correction RFC2733

  • Deployed at RTP level to cope with lost IP datagrams

  • FEC protection data is embedded in regular RTP packets with a specific payload type

  • Relies on simple XOR (⊕) arithmetics :

    If P=A⊕B⊕C,

    then one with only A,B,P can retrieve C with C=A⊕B⊕P


Fundamentals row fec principle

Pkt 3

Pkt 3

Pkt n+3

Pkt n+1

Pkt 1

Pkt n+2

Pkt 2

Pkt 5

Pkt 4

Pkt 3

Pkt n

Pkt 1

Pkt 2

Pkt n

Pkt n+1

Pkt n+2

Pkt 2

Pkt 5

Pkt 1

Pkt 4

FEC 1

FEC 1

FEC (n+2)/3

FEC (n+2)/3

RTP stream with embedded FEC

Fundamentals : Row FEC principle

RTP stream to protect

 Most simple FEC

 Low latency mechanism

 Can only protect from single packet loss


1d column fec overview

3L-1

L

(D-1)L

DL-1

(D-1)L+2

1

L-1

2

L+1

2L+1

0

L+2

2L-1

3L+2

4L-1

3L

(D-1)L+1

2L+2

2L

Pkt 3L+1

FEC C1

FEC C0

FEC C2

FEC CL-1

RTP

&

RTP-FEC combiner

L Columns

1D column FEC overview

RTP stream to protect

D rows


Example of correction hits

1 and at most 1 data packet per column

burst of L consecutive data packets

0

1

2

3

4

0

1

2

3

4

5

6

7

8

9

10

11

6

7

8

9

14

15

16

17

16

17

18

19

20

21

22

23

18

19

20

21

22

23

24

25

27

28

29

24

25

26

27

28

29

30

31

32

33

34

35

30

31

32

33

34

35

FEC0

FEC1

FEC2

FEC4

FEC5

FEC0

FEC1

FEC2

FEC3

FEC4

FEC5

Example of correction hits


Example of correction failures

2 data packets on the same column

1 data packet and its associated FEC packet

0

1

2

3

4

5

0

1

2

3

4

5

6

7

8

9

10

11

6

7

8

9

10

11

12

13

15

16

17

12

13

14

16

17

18

19

20

21

22

23

18

19

20

21

22

23

24

25

27

28

29

24

25

26

27

28

29

30

31

32

33

34

35

30

31

32

33

34

35

?

FEC0

FEC1

FEC2

FEC3

FEC4

FEC5

FEC0

FEC1

FEC2

FEC4

FEC5

?

?

Example of correction failures


2d fec scheme overview

Pkt 3L+1

2

L-1

0

1

(D-1)L+2

L

(D-1)L

L+1

2L

DL-1

L+2

2L+1

3L-1

2L+2

3L

2L-1

4L-1

3L+2

(D-1)L+1

FEC R0

FEC R1

FEC R2

D rows

FEC C0

FEC C2

FEC C1

FEC CL-1

FEC R3

FEC RD-1

RTP

&

RTP-FEC combiner

L Columns

2D – FEC scheme overview

RTP stream to protect


Sample correction hit

0

1

3

2

4

5

FEC’0

FEC’0

6

7

8

9

10

11

FEC’1

FEC’1

12

13

14

15

16

17

18

19

20

21

22

23

FEC’3

FEC’3

24

28

25

26

27

29

FEC’4

FEC’4

30

31

32

33

34

35

FEC’5

FEC’5

FEC0

FEC0

FEC3

FEC1

FEC4

FEC1

FEC2

FEC3

FEC4

FEC5

Sample correction hit

6x6 data matrix with 9 data packets lost and 1 FEC packet lost

1

3

8

21

25

28

29

30

33

The 9 missing data packets are successfully recovered !!!


Sample correction failures

1 data packet and its 2 associated FEC packets

4 data packets positioned on exactly2 rows and 2 columns

0

1

2

3

4

5

FEC’0

0

1

2

3

4

5

FEC’0

6

7

8

9

10

11

FEC’1

6

7

8

9

10

11

FEC’1

12

13

14

16

17

12

13

14

17

FEC’2

18

19

20

21

22

23

FEC’3

18

19

20

23

FEC’3

24

25

26

27

28

29

FEC’4

24

25

26

27

28

29

FEC’4

?

30

31

32

33

34

35

FEC’5

30

31

32

33

34

35

FEC’5

?

FEC0

FEC1

FEC2

FEC4

FEC5

FEC0

FEC1

FEC2

FEC3

FEC4

FEC5

Sample correction failures


Video fec data streams

UDP Port n

Column FEC packets

Row FEC packets

MPEG-TS packets

UDP Port n+2

IP

IP

IP

RTP

RTP

RTP

UDP

UDP

UDP

UDP Port n+4

Same destination IP address (unicast node or multicast group)

Video & FEC data & streams

  • Elegant, does not break the original AV stream

  • A receiving party can use :

    • Just the original encapsulated A/V stream it is not FEC-capable

    • Use the row or column FEC data if only 1D-FEC capable

    • Use both row & column FEC streams if 2D-FEC capable

Media


Typical performance

In seconds

In days !

Typical performance

Reference :

Video at 4Mb/s transported with 7 MPEG-2 TS packets per RTP/IP datagram

  • Legend:

  • L : matrix row length

  • D : matrix column depth

  • I : Interleaving depth used in FEC packets sequencing

  • PLR : Network Packet Loss Ratio

  • MTBE : Mean Time Between Errors

  • Error distribution: random/uniform

2D FEC

Column only 1D FEC

Row only 1D FEC


Status

Status

  • First complete 2D FEC unveiled at IBC’04 by Thomson/Grass Valley

  • Interop session held at the joint Vidtrans/SMPTE conference (On January 30..Feb 2, 2005 in Atlanta, GA), showed full interop of 1D FEC between manufacturers.

  • CoP#3 adopted by Video Services Forum (VSF)

Pro-MPEG CoP#3 FEC is widely accepted as the recommended solution for high quality video contribution on IP


Perspectives

Perspectives

  • FEC on the access network, down to the STBs (under consideration by DVB-IP)

  • Further work in the uncompressed world

    Proposed Pro-MPEG Forum CoP#4, still leaves room for improvements (latency, etc)


Thank you for your attention

Thank you for your attention !

[email protected]

http://www.thomsongrassvalley.com/


  • Login