QAM Output¶

Mcaster allows you to push streams to ATSC-C cable network without need to use additional modulation devices. In this case, a TBS card (currently we support TBS6014) works as a signal generator for modulation of an MPTS (multiplexer), i.e. converting it to QAM signal that can be transported to cable networks for TV broadcasting.

Hardware Requirements¶

To configure QAM output, you need a TBS card (currently TBS6014 is supported) that works as a signal generator for modulation.

DVB Card Configuration¶

To configure such a pusher, first add to the configuration a DVB card with the following necessary parameters:

• hw – the device model, its value should be tbs6014
• adapter – adapter number
• port – port number

Example:

dvb_card tbsmod01 {
  hw tbs6014;
  adapter 0;
  frequency 62000000;
  modulation qam256;
  interleave 3;
  gain 5;
  port 0;
  input_bitrate 38;
}

Optional Parameters¶

• frequency — the carrier frequency (MHz) of the multiplexer for this channel
• modulation — TBS modulation method
• interleave — use interleaver. The interleaver disperses sequence of bits in bit stream to minimize effect of burst errors during transmission
• gain — adjust the output gain to the specified value in dB
• input_bitrate — input bitrate, in Mbps

Multiplexer Configuration¶

Then configure a multiplexer with the option push dvb://tbsmod01. For example:

stream channel1 {
  input udp://239.0.0.1:1234;
}
stream channel2 {
  input udp://239.0.0.2:1234;
}
transponder newMultiplexer1 {
  bitrate 26970k;
  push dvb://tbsmod01;
  program 100 {
    source channel1;
    title Channel1;
    lcn 0;
    service_type digital_tv_avc_sd;
    pid 101 pmt  pmt;
    pid 102 v1 bitrate=2000 pcr ;
    pid 103 a1 bitrate=500  ;
  }
  program 200 {
    source channel2;
    title Channel2;
    lcn 1;
    service_type digital_tv_avc_sd;
    pid 201 pmt  pmt;
    pid 202 v1 bitrate=500 pcr ;
    pid 203 a1 bitrate=100  ; 
  }
}

Modulation Methods¶

When choosing the multiplexer bitrate, keep in mind the used modulation method because it can limit the ability to accept the data:

• QAM64 — maximal possible bitrate 26.90735 Mbit/s
• QAM256 — maximal possible bitrate 38.81070 Mbit/s

Applications¶

QAM output is used in various scenarios:

• Cable television networks
• ATSC-C broadcasting
• Local cable headend systems
• Professional video distribution
• Multi-channel broadcasting

Supported Standards¶

The module supports:

• ATSC-C cable standards
• QAM modulation (64-QAM, 256-QAM)
• MPTS (Multi-Program Transport Stream) output
• Professional cable network integration