Receiving and Rebroadcasting the Teletext Batches

teletext.jpgNote: the function is available starting from the version 1.8.121

Teletext is the system for transfer of digital data as a part of the analogue TV signal, HD/SD SDI signals and as a part of DVB IP/ASI transport streams.

This technology provides transfer of data and simple images. The information is organized as the fullscreen text pages transferred by turns.

Functionality of the SL NEO platform allows implementing the following operations with the teletext data:

·         Receiving and forming the World System Teletext (WST, ITU-R System B Teletext) batches as a part of:

    VBI - the interval SD SDI or an analogue signal (PAL, Y component, 6...22/319...335 line); 






    Vertical ancillary data space (VANC) - the interval of HD/SD SDI signals;


    DVB - IP/ASI transport streams.

·         on-line rebroadcasting the teletext batches received from the central station, from the SL NEO server input to the output, including insert of the regional commercials and during the local "LIVE" broadcasts;

·         recording and rebroadcasting the teletext data  


  when broadcasting with delay the signal from the central station, and when using the module Time Shift;

·         saving the teletext data when recording the input signal to files, generation of batches during the playout of files;

·         remultiplexing the teletext data when forming output signals: VBI-VANC-DVB, in any combinations.

In case of presence of WST-teletext data in the input signal, it is automatically detected and captured, there's no need in additional configuring the software modules Capture and Time Shift.

Functions of capturing and generation of data in VBI/VANC intervals are supported for the Matrox boards of DSX series.

On-line rebroadcasting the teletext batches from the SL NEO server input to its output

Step 1. Configure the mode of rebroadcasting the teletext data while executing the playlist (module Program Player).

For pass-through rebroadcasting the input batches during the insert of regional commercials, you should configure the module Program Player that is responsible for forming the program channel (Program Channel). Configuring is implemented from the control web-console: menu section Manage, item Program Outputs.




Find the item Playout Parameters in the chosen channel Program Channel and activate the item Teletext PassThroughThis mode implements permanent rebroadcasting the teletext data from the input of the first “lower" layer that has the teletext, to the output of the module Program Player.

Graphics Layers.jpgSL NEO platform works with eleven video layers (nine of them are the graphic layers). The "lowest" fullscreen layer (Background), as a rule, is used as a source of the input live-stream. When the playlist is stopped, the stream set for Background, is broadcasted to the output of the module Program Player. When the playlist is being executed, file playout overlaps the input signal. 


Thus, when using Background as a source of an input signal and in case, if the input signal contains the teletext data, this data will be rebroadcasted to the output of the module Program Player (if the parameter Teletext PassThrough is active).


During playout of file materials as a part of a playlist, the input teletext batches also will be permanently presented in the output stream; if the media-files contain the teletext data, this data will be ignored. 


For activating this mode, you should set the background source for the program channel (module Program Player): the Capture service will be the background source. The configuring procedure is implemented from the control web-console: menu section Status, window Program. You should choose the item Background in the window, then specify a type of source LIVE for it and choose the appropriate capture service Capture.


The second possible variant of work is playout of file materials that contain teletext data jointly with the LIVE-clips that refer to the sources of input signals. In this case you should turn off the Background layer by setting a type of source NONE for it. Now the main fullscreen layer (Main Playlist Layer) becomes the first “lower" layer that will contain the teletext data. Work in this layer will allow broadcasting the teletext data contained in file materials and input LIVE-streams, by turns.


LIVE is a specialized type of clip at the server database that contains a link not to the media-file, but to the source of a signal/source. You may create a few clips, according to the number of server inputs, and use them in the broadcasting playlist in future. 

new_live_clip.jpgCreating LIVE-clips is implemented in the client application Air Manager, when working server software. The command New/Local Stream at the right part of the Media Browser window allows the user to create a new clip that contains a link to the source of a signal/stream.


In the field Video Mode you can choose a standard of input video; in the field Local Stream name specify a name of an appropriate capture service Capture. You can view the list and names of configured services in the field Status of the server control panel.


Let's get back to the parameter Teletext PassThrough: if it's not active, forming the teletext data at the output of the appropriate Program Player module will be completely turned off. 


Step 2.Configuring the output board/interface


DVB-teletext as a part of IP TS


ttx2.jpgLet's configure the parameters of the output interface in the control web-console: menu section Manage, item Video IO Boards.


Choose the service Playout in the section LAN Interfaces/Ethernet Adaptor, then click Edit and choose the item Teletext in the window MPEG2 TS Parameters.


Activate the item DVB Teletext, in the field Teletext PID specify the value of the appropriate identifier, or leave the field empty if the value is Auto.


Open the field Subtitle Lang and choose the language for captions within the teletext stream, in the field Subtitle Page set the number of the page that contains captions (as a rule, it's 888).


Save the settings: press Apply Changes at the top part of the control console window.


Teletext batches as a part of VBI or VANC


Configure the parameters of the I/O board in the control web-console: menu section Manage, item Video IO Boards. Choose the Playout service in the section Matrox DSX, click Edit, find the field General and activate the item Use VANC for generation of VANC-data. If the parameter is inactive, data will be formed in VBI lines, according to ITU-R BT.653.




Save the settings: press Apply Changes at the top part of the control console window.

Example: the regional insert with a signal from the studio, with rebroadcasting teletext

Let's consider the situation. SL NEO server has 2 inputs: one of them receives the program signal containing teletext from the central station, the second input receives a signal without the teletext from the studio. It is necessary to organize local broadcasting with commercial inserts and news broadcasts from the studio, with constant presence of the teletext data from the central station in the output signal.


To solve this problem, you should set the background source for the program channel (module Program Player): the Capture service that receives the signal from the center will be this source. The parameter Teletext PassThrough should be active: it will give a possibility of constant rebroadcasting the teletext to the server output.


The signal sent from the studio requires adjusting a LIVE-clip that refers to the appropriate capture service. This clip will be used in the playlist equally with the file materials.


Thus, when the playlist is stopped, the signal from the central station will be broadcasted to the output together with the teletext; during the playlist execution, the teletext batches will be also presented in the output signal.

Record with saving batches, viewing information about the presence of teletext data

Saving the batches World System Teletext is implemented automatically in the process of recording signals into the media-files, you don't need to implement additional adjustments in the program module Recorder.


ttx4.jpgSL NEO platform software allows you to check the presence of teletext data in the recorded files.


The window File Monitor of the application Air Manager displays the service information about the data presence. This operation also works for LIVE-clips.


Activation of the mode for displaying batches is implemented in the menu for configuring Air Manager: File-> Configure-> Preview-> item Show ANC.


The information about the presence of teletext data is also displayed in properties of the clip placed at the server database (right click in the window Media Browser of the application Air Manager and choose Show Info). The information is displayed in the section of the clip properties - Profiles/ANC Data.