7/21/2008
7/18/2008
MPEG-2 Transport Streams
Pro MPEG Forum CoP3 or SMPTE 2022
Introduction
Pro-MPEG Forum Code of Practice #3 release 2 (CoP3) or SMPTE 2022-2007, describe how MPEG-2 Transport Streams (MPEG-2 TS) should be encapsulated when sent over IP networks. It also describes a forward error correction (FEC) mechanism that can be used to correct errors than can occur during the transport. This article will explain how video content can be sent over IP networks and how errors can be corrected using CoP3 FEC.
ASI to IP
All MPEG-2 transport streams shall be encapsulated in RTP (Real-time Transport Protocol) according to RFC 1889 in conjunction with RFC 2250. Transport service is provided jointly by UDP (checksum and multiplexing) and RTP (sequencing and time stamping / jitter removing). RTP always uses an even UDP port number.
Pro-MPEG Forum Code of Practice #3 release 2 (CoP3) or SMPTE 2022-2007, describe how MPEG-2 Transport Streams (MPEG-2 TS) should be encapsulated when sent over IP networks. It also describes a forward error correction (FEC) mechanism that can be used to correct errors than can occur during the transport. This article will explain how video content can be sent over IP networks and how errors can be corrected using CoP3 FEC.
ASI to IP
All MPEG-2 transport streams shall be encapsulated in RTP (Real-time Transport Protocol) according to RFC 1889 in conjunction with RFC 2250. Transport service is provided jointly by UDP (checksum and multiplexing) and RTP (sequencing and time stamping / jitter removing). RTP always uses an even UDP port number.
For most streams, the RTP/UDP/IP overhead of 40 bytes per RTP packet is relatively low (for example 3% with a 1 316 byte payload).
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IP packets can carry from 1 to 7 TS packets, knowing that:
The time stamp field in the RTP header is based on the PCR values from MPEG-2 with a resolution of 90 Khz.
Streams must include:
RTCP (Real-time Transport Control Protocol) can be included to periodically inform the sending side about network quality (e.g. lost packets, delay, jitter, etc.).
At the output of the IP network, the delivered Transport Stream must be fully ISO/IEC 13818-1 compliant (40ms maximum jitter, 1 artifact every hour, etc.).
What about error protection ?
Code of Practice #3 describes a Forward Error Correction (FEC) method for protection against errors in delivering professional MPEG-2 TS data over IP networks. With that method implemented in IP video gateays, packet errors, out of order packets, network jitter and delay can be compensated.
FEC data insertion is done in real-time along with TS over IP encapsulation: Protection data is calculated and embedded in regular RTP packets with a specific payload type.
It relies on simple XOR arithmetics:
if F=A B C, then if only A,B,F are present, C can be recovered.
A FEC matrix is generated and transmitted on two separate UDP ports:
FEC columns on UDP port + 2
FEC rows on UDP port + 4
- The overall size of RTP payload must not exceed the MTU (Maximum Transfer Unit) in order to prevent RTP packets fragmentation around the network
- Short packets induce high overhead
The time stamp field in the RTP header is based on the PCR values from MPEG-2 with a resolution of 90 Khz.
Streams must include:
- Program Association Table (PAT)
- Program Map Table (PMT)
RTCP (Real-time Transport Control Protocol) can be included to periodically inform the sending side about network quality (e.g. lost packets, delay, jitter, etc.).
At the output of the IP network, the delivered Transport Stream must be fully ISO/IEC 13818-1 compliant (40ms maximum jitter, 1 artifact every hour, etc.).
What about error protection ?
Code of Practice #3 describes a Forward Error Correction (FEC) method for protection against errors in delivering professional MPEG-2 TS data over IP networks. With that method implemented in IP video gateays, packet errors, out of order packets, network jitter and delay can be compensated.
FEC data insertion is done in real-time along with TS over IP encapsulation: Protection data is calculated and embedded in regular RTP packets with a specific payload type.
It relies on simple XOR arithmetics:
if F=A B C, then if only A,B,F are present, C can be recovered.
A FEC matrix is generated and transmitted on two separate UDP ports:
FEC columns on UDP port + 2
FEC rows on UDP port + 4
FEC Matrix is computed as follows:
FEC packets can be computed for both columns and lines. One FEC packet is able to recover one lost RTP packet in a column/row. If several packets are lost in the same column for instance, FEC packet for rows can be used to re-generate the packet.
7/15/2008
Internetwork Expert - CCIE R&S Workbook Vol1, Ver5
There is new version (ver5) of the R&S workbook vol 1. IE completely changed their style in this version of the workbook. The only bad thing I am seeing is they could be more detailed in their explanations but it's only a BETA.
7/14/2008
7/13/2008
7/09/2008
Mercedes to cut petroleum out of lineup by 2015
By Jaymi Heimbuch Posted Thu Jun 26, 2008 9:23am PDT
In less than 7 years, Mercedes-Benz plans to ditch petroleum-powered vehicles from its lineup. Focusing on electric, fuel cell, and biofuels, the company is revving up research in alternative fuel sources and efficiency.
The German car company has a few new power-trains in the line-up that European journalists have had the opportunity to test out in the Mercedes facility in Spain. One vehicle includes the F700, powered by a DiesOtto engine that combines HCCI and spark ignition to get nearly the same efficiency as diesel, but minus the expensive after-treatment systems.
The engine can run on biofuels, and we may have a purchasable vehicle by 2010 -- a year that seems to be popular for the debut of a lot of new alternative fuel car models, making ’08 and ’09 simply thumb-twiddling years for consumers. I don’t know, maybe car makers just like the roundness of “2010.” The company’s next big step will be to launch a Smart electric car which is fuel and emission-free.
Anyway, Mercedes is looking into electric vehicles, both battery-powered and fuel-cell powered. Not only are models in development, but we’ve also seen the company making steps towards its zero-petroleum goal right now, from better cabs in London to li-ion battery improvements. The company also has about 100 Smart electric cars undergoing testing in London, with that favorite 2010 year as the projected market release date.
Mercedes is making serious investments, already putting nearly $4 million into the pot of its long-term Sustainable Mobility plan, with another nearly $1.4 billion going in before 2014.
While car models may be able to run on fuels other than gasoline or diesel, we have yet to find a method of both running and producing vehicles entirely free of fossil fuels. I’m waiting for a mainstream car line that creates renewable fuel, clean-running vehicles out of 100% recycled materials in plants run on 100% renewable, clean power … Will I even be alive when that finally happens? I have hope.
Via AutoblogGreen, The Sun; Photo Leonid Mamchenkov
source: http://green.yahoo.com/blog/ecogeek/603/mercedes-to-cut-petroleum-out-of-lineup-by-2015.html
In less than 7 years, Mercedes-Benz plans to ditch petroleum-powered vehicles from its lineup. Focusing on electric, fuel cell, and biofuels, the company is revving up research in alternative fuel sources and efficiency.
The German car company has a few new power-trains in the line-up that European journalists have had the opportunity to test out in the Mercedes facility in Spain. One vehicle includes the F700, powered by a DiesOtto engine that combines HCCI and spark ignition to get nearly the same efficiency as diesel, but minus the expensive after-treatment systems.
The engine can run on biofuels, and we may have a purchasable vehicle by 2010 -- a year that seems to be popular for the debut of a lot of new alternative fuel car models, making ’08 and ’09 simply thumb-twiddling years for consumers. I don’t know, maybe car makers just like the roundness of “2010.” The company’s next big step will be to launch a Smart electric car which is fuel and emission-free.
Anyway, Mercedes is looking into electric vehicles, both battery-powered and fuel-cell powered. Not only are models in development, but we’ve also seen the company making steps towards its zero-petroleum goal right now, from better cabs in London to li-ion battery improvements. The company also has about 100 Smart electric cars undergoing testing in London, with that favorite 2010 year as the projected market release date.
Mercedes is making serious investments, already putting nearly $4 million into the pot of its long-term Sustainable Mobility plan, with another nearly $1.4 billion going in before 2014.
While car models may be able to run on fuels other than gasoline or diesel, we have yet to find a method of both running and producing vehicles entirely free of fossil fuels. I’m waiting for a mainstream car line that creates renewable fuel, clean-running vehicles out of 100% recycled materials in plants run on 100% renewable, clean power … Will I even be alive when that finally happens? I have hope.
Via AutoblogGreen, The Sun; Photo Leonid Mamchenkov
source: http://green.yahoo.com/blog/ecogeek/603/mercedes-to-cut-petroleum-out-of-lineup-by-2015.html
7/07/2008
Vegetarianism proves to be perversion of nature
Vegetarians can be referred to as true fanatics. On the other hand, they are seriously misled in their beliefs. Practically nobody argues with them, since it is really difficult to convince a vegetarian of his or her self-deception. May be that is the reason why the vegetarian movement develops so actively around the globe and continues to recruit many new members.
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Soured milk – 90%
Fresh milk – 83%
Beef – 76%
Cottage cheese – 75%
Compare this data with that concerning vegetable protein:
Wheat bread – 52%
This is the main reason why dietitians recommend to consume 60 percent of animal protein and 40 percent of vegetable analogue from the daily ration.
No vitamins and mineral substances are of any use if our organism does not receive animal protein. Like vegetable protein, they can not be digested without animal protein.
Vegetarians, especially those of advanced age, usually face numerous health problems that are mainly caused with the shortage of animal protein. After two months of no-meat diet, the quantity of protein in the cardiac muscle decreases four times, which triggers the development of heart failure. The work of all other organs worsens soon after. A vegetarian man or woman may find themselves on the brink of dystrophy.
First signs of dystrophy are not that evident and burdensome, but the resulting effect may lead to lamentable consequences. Have you ever seen starving African children on TV? Then you must remember those thin legs and swelled bellies, which dystrophy causes.
source: pravda.ru
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