Meteosat-8/9 Data Flow

1. Data is transmitted from the Meteosat-8/9 (MSG-1/2) spacecraft down to Earth stations in Germany.
2. That data is refined, compressed and encoded as HRIT and LRIT files.
3. The HRIT and LRIT files are added to the EUMETCast service
4. The EUMETCast data is sent up to the Eurobird-9 satellite in small packets of data.
5. Other packets of data, such as Foreign Satellite Data (FSD), Rapid Scanning Service (RSS), ATOVS and EARS files, are also sent up to Eurobird-9, but with different packet identifiers (PIDs).
6. Your dish, LNB, and Skystar2 card receive the packets of data.
7. The Server4PC turns the data packets into a TCP/IP stream, passing only the PIDs you have selected.
8. The T-Systems TelliCast software recovers the files from the TCP/IP stream, looking only at the data channel names you have selected.
9. The MSG Data Manager software turns the files into images.
10. The MSG Animator software provides quick-look, real-time animations
11. The GeoSatSignal software turns the images into multi-channel, false-colour, remapped animations.

My PC Configuration

What does the DVB card and its software do?

Based on tests we needed to do for Windows Vista, my understanding of what happens between the DVB card and the TelliCast software has increased a little.

There is a network device driver named SKYnet.sys, DVBnet.sys (or similar) which provides the network interface.  As far as the operating system is concerned, this is a network driver and it is the device to which you assign the address 192.168.238.238.  It therefore appears capable of talking to other devices or networks connected to the virtual LAN adapter on that address.  The PC thinks it has two network cards, and needs to decide which one to use to talk to any external connection, and this has implications for Windows Vista.  

The software associated with the SkyStar2 card or USB box you are using talks to the device driver, converting packets received from the satellite from DVB packets to Internet packets.  Each DVB packet has a packet identifier (PID), which associates it with a particular hardware origination address (the MAC address).  Within each PID, there can be one or more data streams (such as Metop data, HRIT data etc.)  By some process which I do not currently understand,  each stream will appear to originate from a particular fixed network address such as 224.223.222.223.  I guess this information is carried in the announcements of the data, but how you you know the address of the announcement channel?  

So the job of the DVB software and network device driver is to turn a stream of DVB packets from a particular PID, into one or more IP data streams which appear to originate from a particular IP address.  What does the TelliCast software do?

The TelliCast software has a number of functions, some of which I understand better than others!

• As the DVB packets come in, the required PIDs are selected by the hardware in the DVB card or USB box.
• Following that filtering, the packets are converted from DVB format to IP format, and given a particular source address.
• When a new set of packets for a source address appears, TelliCast is given the chance to register an interest, and request a connection.
• For each source address, if the TelliCast software has requested the data, the IP format packets are sent to the DVB network software.
• The DVB network software makes the packets appear to have come from a real network adapter, and sends them to the operating system.
• The TelliCast software picks up those packets from the operating system via standard network I/O calls.
• TelliCast performs some error detection and correction.
• TelliCast stores the file fragments in a local buffer, or on disk in the FSY file.
• Finally, TelliCast assembles complete files from the incoming and/or saved packets.

In more detail:

• When the TelliCast software starts, it must establish a connection to the DVB network software on 192.168.238.238.  While this connection is being established, the yellow icon is displayed.  If the connection fails, a red icon is displayed, and if it succeeds, a "pink" icon is displayed.  This requires the ability of the program to connect outwards, and a firewall entry may be required to allow this to happen.
• Somehow the software registers an interest in UDP data from the DVB network.
• It then needs to connect to the "Announcement" channel, which has an address of: 224.223.222.223:4711.  The name and address of this channel are defined in the recv.ini file.
• When a new set of files are ready to be sent over EUMETCast, a message is sent to the announcement channel, and hence to the TelliCast software.  The TelliCast software will check whether the user wants this data (by checking the entries in the recv-channels.ini file), and whether the user is authorised for this data.  If the data is wanted and authorised, the TelliCast software will try and make a connection with the DVB network software so that the following UDP data is sent to the TelliCast application.

I am sure that a large part of this is setting up and using a standard UDP data transaction, but I still have to find a good description of that on the Internet.

More information and images

• MSG-1 & ATOVS
• MSG Data Manager Software
• MSG Animator software
• GeoSatSignal Software
• Configuring your PC
• FAQ
• Yahoo! MSG-1 and EUMETCast User Group
• EUMETSAT's trouble-shooting guide
• Early Meteosat-8 images and animations
• Glossary of terms

Automated system monitoring tools

• Using the Setup4PC tools
• Using the TelliCast tools
• Using SNMP to show the data flow

 

Copyright © David Taylor, Edinburgh

Last modified: 2009 Dec 03 at 13:31