Ondems Media Gateway – Release 1.2 Real-Time
Contents
1. channel from Transponder 3 has the PMT 301 the video PID 310 and the audio PID 311 The Multiplexer puts together all the 3 Transponders by changing the PID of the PAT from Transponder 1 from 0 to 1 The PIDs of the Transponders 2 and 3 are changed from O to 2 and respectively 3 The PID of the audio channel from Transponder 1 is changed from 211 to 111 otherwise it would collide with the audio PID from the first channel of the second Transponder which has the same value 211 We want to send each of these four channels on a separate multicast address Each channel should have proper PAT and each PID should be the original PID found in the original Transponder See Fig 3 w A 3 s _DVB S T C DVB Receiver A _ s _DYB S T C w DVB Receiver A _ P DVB S T C DVB Receiver eee od PIDs 1 2 3 101 110 1 11 PIDs 0 101 110 2 MCAST 301 202 210 211 220 221301310311 MCAST Multiplexed Individual Channels Transponders multicast Figure 3 Using the Media Gateway for multicasting several multiplexed Transponders This solution requires the following configuration file card_type 120 card no 0 channel no 0 E 9203162000170 101 JI JAI 7217 ZO I2ZH0 A A000 770 ZOLZ1O 211 239 192 30 332000 270202 220 221 239 419220 422000 3 0 301 310 311 The above configuration file will initialize the first installed DEKTEC DTA 120 on the first input channel2. Media Gateway for multicasting a single Transponder received ae a DVB receiver This solution requires the following configuration file card_type 120 card no 0 channel no 0 LOT itIZ2 0e4i620000 HA 126 290 239 019220 2 20007ECI 128 0 65 129257 ZIP ease od The above configuration file will initialize the first installed DEKTEC DTA 120 on the first input channel Ond emas Ondems Media Gateway Date Mar 2 2005 User Manual Version 1 2 1 Page 7 10 streaming into your world The incoming traffic will be multicasted as follows e The PIDs 0 64 128 and 256 will be forwarded to the multicast address 239 192 0 1 2000 The PAT PID 0 will be stripped so that it will contain only the multicasted channel e The PIDs 0 65 129 and 257 will be forwarded to the multicast address 239 192 0 2 2000 with a TTL value of 128 e All the incoming traffic will be forwarded to the multicast address 239 192 0 3 2000 3 2 Example 2 receiving and multicasting several multiplexed transponders Let us assume now that that the ASI card DTA 120 receives three transponders Transponders 1 and 3 have one channel each Transponder 2 has two channels The channel from Transponder has the PMT PID 101 the video PID 110 and the audio PID 211 The first channel from Transponder 2 has the PMT PID 201 the video PID 210 and the audio PID 211 The second channel from Transponder 2 has the PMT PID 202 the video PID 220 and the audio PID 221 The
3. one multicast address If none of the selected PIDs are found in the PAT the content of the PAT table is not modified The format of the configuration file is the following card_type 120 140 card no value Channel _no value multicast_ip port ttl value all pids multicast_ip port ttl value pid0 new_pid0 pidi new pidil Currently the following ASI cards are supported e DEKTEC DTA 120 IN card_type 120 e DEKTEC DTA 140 IN OUT card_type 140 If the TTL Time To Live parameter is not specified a default value of 1 is set for that multicast address 3 1 Example 1 receiving and multicasting one transponder Let us suppose that the ASI card DTA 120 receives one transponder that has two TV channels The first channel has the PMT PID 64 the video PID 128 and the audio PID 256 The second channel has the PMT PID 65 the video PID 129 and the audio PID 257 We want to send each of these channels on a separate multicast address Each channel should have proper PAT In addition to this we would also like to send the whole transponder to a third multicast address See Fig 2 aa N MCAST BB XN J 1 i loste p i ns 2 E d al DVB S T C DVB Receiver eat Z gt z B V TIE a oe i PIDs 0 64 65 128 129 PIDs 0 64 128 256 MCAST ae eros ossi22s7 airi PIDs 0 65 129 257 PIDs 0 64 65 128 Transponder Individual Channels Multiplex multicast Figure 2 Using the
4. streaming into your world Ondemas Ondems Media Gateway Date Mar 2 2005 User Manual Version 1 2 1 Page 8 10 The incoming traffic will be multicasted as follows The PIDs 1 101 110 and 111 will be forwarded to the multicast address 239 192 0 1 2000 Before being multicasted TS packets with the PID 1 PAT will have the PID changed to 0 Similarly TS packets with the PID 111 will have the PID changed to 211 There is no need for PAT change since the initial Transponder only contained one channel The PIDs 2 201 210 and 211 will be forwarded to the multicast address 239 192 0 2 2000 Before being multicasted TS packets with the PID 2 PAT will have the PID changed to O and the PAT table will be stripped so that it will contain only the multicasted channel The PIDs 2 202 220 and 221 will be forwarded to the multicast address 239 192 0 3 2000 Before being multicasted TS packets with the PID 2 PAT will have the PID changed to O and the PAT table will be stripped so that it will contain only the multicasted channel The PIDs 3 301 310 and 311 will be forwarded to the multicast address 239 192 0 4 2000 Before being multicasted TS packets with the PID 3 PAT will have the PID changed to 0 There is no need for PAT change since the initial Transponder only contained one channel 4 Other solutions from Ondems Ondems is a company creating software products in the area of transport of digital television streams MPEG 2 o
5. 27Mhz clock for the stream 6 3 Transport Stream Structure The MPEG 2 Transport Stream is composed by one or more Program Elementary Streams PES each of these streams is encapsulated in Transport Stream packets with different PID values Apart from Program Elementary Streams in the Transport Stream there are Service Information tables encapsulated with the according PID values Some of the PID values are reserved for special Service Information tables Value 0 is reserved for Program Association Table 1 is reserved for Conditional Access Table values between 2 and 31 are reserved for DVB Service Information Tables and the value of 8191 is reserved for Null packets The Null packets are inserted in the stream to shape it to a constant bitrate form These Null packets are discarded by the receivers 6 4 Service Information Tables Program Association Table PAT maintains the list of the programs for each program the information that is stored is the PID value of the Program Map Table Program Map Table PMT maintains the list of the PID values of the streams within the program video audio subtitle Each program is driven by its own PCR clock The PCR PID is also provided in the PMT Apart from MPEG 2 Service Information tables the DVB Service Information tables provide an extended range of services on top of the standard Service Information tables e Event Information Tables EIT provide Electronic Program Guide EPG for present follo
6. Ond ems Ondems Media Gateway Date Mar 2 2005 User Manual Version 1 2 1 Page 1 10 streaming into your world Ondems Media Gateway Release 1 2 Real Time conversion between different I O standards 1 Overview In building heterogeneous Digital TV delivery systems it is often required to interconnect equipment that has incompatible interfaces ASI Ethernet IP In this case a reliable solution is provided by Ondems Media Gateway 1 1 Product description Ondems Media Gateway is a software product used for transferring the MPEG2 Transport Stream packets between DVB ASI interfaces and Multicast IP environment It runs on a standard PC with Linux operating system The interfaces used for I O are an ASI card provided by DEKTEC and an Ethernet card The most common use for the Media Gateway is in IP TV systems where it is used to receive MPEG 2 multiplexes from professional DVB receivers with ASI output demultiplex the received MPEG 2 multiplex and multicast the data based on configurable rules eo l _DVB S T C rd Party DVB Receiver and Transrater Headend Server Side Client Side Figure 1 The use of Ondems Media Gateway in IP TV solutions Ondems Media Gateway is de multiplexing the MPEG2 Transport Stream and sends each packet to selected one or more multicast addresses The selection is made on PID value The packets are sent in the received order The Media Gateway automa
7. and does NOT display any output the ASI driver is properly installed and now loaded If the command displays some output it is usually an error If the error is modprobe Can t locate module Dtalxx it means that you do not have the DEKTEC driver installed To install the DEKTEC driver please refer to the next section If the output is different from the above messages it means that the driver is installed but it could not be loaded The output should contain relevant error messages Please send this output to Ondems or DEKTEC for troubleshooting If you have the DEKTEC driver installed please also check at this point if the driver binds are present In order to do this please type ls dev Dtalxx The above command should display several lines of output similar with the following lines dev Dtalxx0 dev Dtalxxl dev Dtalxx2 dev Dtalxx3 dev Dtalxx4 dev Dta5xx0 dev Dta6xxl dev Dta7xx2 dev Dta8xx3 dev Dta9xx4 If there is NO output then the driver bindings are not present Please go to the driver directory LinuxSDK Dtalxx and type the following command sh Dtalxx init start Ondemas Ondems Media Gateway Date Mar 2 2005 User Manual Version 1 2 1 Page 4 10 streaming into your world 2 2 1 Installing the DEKTEC driver 1 Download the DEKTEC driver from the DEKTEC web page http www dektec com The name of the package is Linux SDK and it is available from the Download section 2 Unpack the
8. ber of your ASI card For example if you are using the Media Gateway with a DTA 140 card the card_type field should have the value of 140 card_type 140 Solution 2 Please check if the DEKTEC driver is installed on your system You can use the following command in order to check if you have the driver installed the command is case sensitive modprope Dtalxx If the command displays some output it is usually an error If the error is modprobe Can t locate module Dtalxx it means that you do not have the DEKTEC driver installed Please download the driver from the DEKTEC website and install it refer to the Installation section If the output is different from the above messages it means that the driver is installed but it could not be loaded The output should contain relevant error messages Please send this output to Ondems or DEKTEC for troubleshooting If the above command modprope Dta1xx does not display any output it may be that the driver failed to load To check if the driver failed to load Please type the dmesg grep Dtal xx command The beginning of the output should be similar with this one Dtalxx Initialising module Dtalxx Found 1 DTA 1xx boards in the system Dtalxx Major 254 Dtalxx The driver Rev 1 2 0 75 has loaded successfully If this is not the case please contact Ondems or DEKTEC including the output of the above command Solution 3 Please check if the device files are created In the d
9. driver unzip TanuxSbDK Zip 3 Go to the driver directory and compile the driver cd LinuxSDK Dtalxx make 4 Install the driver make install 5 Post installation mandatory sh Dialxx 1nit start Please also refer to the DEKTEC documentation included in the package 2 3 Installing the Media Gateway 1 Place your license file ondems license in the etc directory 2 Install the rpm package rpm i media gateway 1 2 1 1586 rpm 3 Modify the configuration file etc media gateway asi2ip config 4 Restart the Media Gateway service etc init d asi2ip restart 5 Check the log file tail f var log asiZip log 2 4 Quick Testing Guide 1 Connect the input to the ASI card 2 Check the log file tail f var log asi2ip log 3 If input is detected bitrate shown and PIDs detected in the stream check the multicast output 2 5 Files Location Media Gateway files are located in usr local Ondems media gateway Media Gateway binary usr local Ondems media gateway asi2ip Media Gateway service script etc init d asi2ip Configuration file the service is disabled if this file does not exist J etc media gateway asiZip config Ondemas Ondems Media Gateway Date Mar 2 2005 User Manual Version 1 2 1 Page 5 10 streaming into your world Examples of configuration files are located in usr local Ondems mediagateway config Installed man pages in usr local man asiZip 1 asiZzip confi
10. ev directory there should be some files used for communicating with the driver These files are of the form dev Dtalxx lt number gt If no file is present you did not install the driver properly Try to run again the driver install script sh Dtalxx init start Ondemas Ondems Media Gateway Date Mar 2 2005 a a Ea e User Manual Version 1 2 1 Page 10 10 6 Background Information 6 1 MPEG 2 Transport Stream Format MPEG 2 combines one or more Packetized Elementary Streams which have a common time base into a single stream There are two formats for MPEG 2 Streams e MPEG 2 Program Stream is using packets of variable and relatively great lengths being suitable in error free environment such as non real time software processing e MPEG 2 Transport Stream is using 188 bytes fixed packet length being suitable for environments where errors are likely such as storage or transmission in lossy or noisy media and real time environment 6 2 Transport Stream Packets MPEG 2 Transport Stream packets are 188 bytes length Each packet has a header with an optional Adaptation Field structure and the payload The important fields in the header are e Synchronization byte with the value of 0x47 in hexadecimal 71 in decimal e PID which select the stream component e Continuity Counter incremented by one for each packet with the current PID e Program Clock Reference is inserted in the Adaptation Field structure of the packet to provide a accurate
11. g 5 When running Ondems Media Gateway will also create the following log file var log asi2ip log 2 6 Starting stopping and verifying the Media Gateway Starting the Media Gateway Jete init d asiZip start Stopping the Media Gateway etc init d asiZzip stop Verify if the Media Gateway is running etc init d asi2ip status Checking if the Media Gateway receives any input tail f var log asi2ip log If the Media Gateway has an input then a non zero bitrate and received PIDs are shown Note Please always use the above commands scripts to start and stop the Media Gateway In addition to starting stopping the Media Gateway the above commands scripts also load unload the ASI drivers Starting the Media Gateway executable asi2ip alone may lead to failure because the ASI driver is not loaded by the Linux kernel Ondemas Ondems Media Gateway Date Mar 2 2005 User Manual Version 1 2 1 Page 6 10 streaming into your world 3 Configuration Ondems Media Gateway supports a plain text configuration file in order to specify the parameters of the input DVB ASI interface and output Multicast IP The Media Gateway demultiplexes the MPEG2 Transport Stream and sends each TS packet to the specified multicast addresses according to its PID value The packets are sent in the same order as they are received The Media Gateway automatically modifies the PAT table PID 0 in order to select only the channels that are sent to
12. inux distributions supported Kernel 2 6 supported e Better error repporting 1 3 2 From version 1 0 to version 1 1 e Better support for temporary licenses improved help and messages e Better driver handling in the start stop script e Improved documentation Ondemas Ondems Media Gateway Date Mar 2 2005 User Manual Version 1 2 1 Page 3 10 streaming into your world 2 Installation Ondems Media Gateway is delivered as an RPM Linux package After installation it provides conversion between ASI and IP as a service in the Linux OS The service is automatically started in the run levels 3 or 5 and stopped in run levels 0 1 2 and 6 However the service might be disabled if the appropriate configuration file does not exist The product has been successfully tested with various versions of the following Linux distributions 2 1 Obtaining a license A license is required in order to install the Ondems Media Gateway software on a 3 party computer This license can be obtain from DEKTEC or Ondems and is provided as a file ondems license This file has to be placed in the etc directory After the Media Gateway is run at least once this file can be removed The license binds the Media Gateway with the ASI card the Media Gateway software will only run on machines that have installed an ASI card for which there is a license There are two types of licenses currently available e Permanent License This license has to be
13. purchases and gives the right to use the Media Gateway software in connection with an ASI card for an unlimited period of time e Temporary License This license can be obtained for free and allows for a limited trial period of the Media Gateway usually 30 days The Temporary License also binds the Media Gateway software with an ASI card The Media Gateway software can only be tried using the ASI card for which the Temporary License was given A Temporary License can only be issued once for an ASI card After the Temporary License expires a Permanent License is required for that ASI card Each time the Media Gateway is started one hour is deducted from the trial time Because of this the Temporary License will expire very quickly if the Media Gateway is restarted very often For example if the Media Gateway is restart every minute a 30 days Temporary License will expire in 12 hours 2 2 Prerequisites In order to install and run the Ondems Media Gateway you need to have e A PC running a supported Linux distribution The PC should have more than 128 MB of RAM and the CPU frequency should be higher that 1 GHz e The PC should have the DEKTEC ASI card installed and a Linux supported Ethernet card port installed available e The driver for the DEKTEC ASI card Dtalxx should be installed You can use the following command in order to check if you have the driver installed the command is case sensitive modprobe Dtalxx If this comm
14. tically modifies the Program Association Table PID 0 in order to maintain the correct list of the channels on each transport stream sent to one multicast address g Ondems Media Gateway Date Mar 2 2005 Ondems Version 1 2 1 streaming into your world User Manual Page 2 10 1 2 Features Technical specifications Some of the options and features presented are customizable depending on the client requirements The features marked with are currently under development Please contact us for further details Ondems Media Gateway Target Digital Television Systems Other Streaming Systems Media Formats DVB compliant MPEG 2 Transport Stream e Single Program Transport Stream SPTS e Multi Program Transport Stream MPTS Input Output e DVB ASI DEKTEC DTA 120 DTA 140 e IP Ethernet 10 100 1000 Base TX e UDP Multicast RTP Multicast e Configurable TTL for Multicast e ATM AALO AAL5 electrical optical e Upto 4 DVB ASI input cards Output rate control e Same as input e Constant by Insertion Removal of Null packets Media Processing e PID filtering e PID value modifications e PAT processing Supported Linux e Mandrake 9 1 9 2 10 0 10 1 Distributions tested SuSE 9 0 e RedHat 9 0 e Other distributions should work as well Please contact Ondems for details and support 1 3 Added features and major modifications 1 3 1 From version 1 1 to version 1 2 e More L
15. ver DVB or IP infrastructures An important part of our policy is the customization of our products in order to fit the customers needs Customization work may include Adding new features to existing products Modifying existing products to fit particular needs Designing and creating customized solutions in order to fit a certain purpose specified by the client Please feel free to ask us for a quotation at info ondems com In addition to Media Gateway Ondems also develops other products related with DVB SI IP TV and VoD For more information please visit our web site at http www ondems com Ond emas Ondems Media Gateway Date Mar 2 2005 User Manual Version 1 2 1 Page 9 10 streaming into your world 5 Troubleshooting Before reporting any problem please verify the log file produced by the Media Gateway tail f var log asi2ip log This log file records in real time the type of input received by the Media Gateway If the desired PIDs are not present in the multicasted output it is possible that they are not received in the input stream When reporting a problem please also send the configuration file etc media gateway asi2ip config and the log file var log asi2ip 1log Problem The Media Gateway does not start and the log file says Error Cannot initialize ASI card with specified parameters Solution 1 Please check first the card type in the configuration file The card_type field should match the num
16. wing schedule events e Time and Date Tables TDT provide generic time information for the TV programs e Time Offset Tables TOT provide local and universal time information for the TV programs allowing advanced Set Top Boxes to take timezones into consideration e Network Information Tables NIT provide network characteristics and frequencies e Service Description Tables SDT provide program name definition All of these DVB Service Information tables are used by the Set Top Box receivers to provide descriptions of the programs and events on the digital television networks This data may also be provided for other transport streams
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