A GNU Radio Based ISDB-T and RTL-SDR Compatible 1Seg Decoder

In most parts of the world the DVB-T standard is used to air digital HDTV. In the USA the ATSC standard is used, and in China DTMB is used instead. In other countries such as Brazil, Peru, Argentina, Chile, Honduras, Venezuela, Ecuador, Costa Rica, Paraguay, Philippines, Bolivia, Nicaragua and Uruguay a third standard called “ISDB-T International” is used which is based on the Japanese ISDB-T standard. 

Digital broadcast standards used in each country.
Digital broadcast standards used in each country.

Recently a team from Uruguay has been working on creating a ISDB-T receiver in GNU Radio. With this decoder ISDB-T signals can be received with a wide bandwidth SDR (needs to be 6MHz or larger) and then decoded into a video file. Because ISDB-T is so similar to DVB-T they have based much of their code on gr-dvbt which is a GNU Radio based DVB-T decoder.

In addition to the ISDB-T decoder, they have also implemented a 1-seg decoder. 1-seg is a mobile HDTV service that exists in Japan, Argentina, Brazil, Chile, Uruguay and Peru. It runs on the ISDB-T system, and is called “1-seg” because it’s data occupies 1-segment of the 13-segment based ISDB-T bandwidth. It is used in small mobile TV receivers, many of which are now built directly into mobile phones sold in countries that use ISDB-T. Due to it’s much lower bandwidth requirement the 1-seg decoder can be used with an RTL-SDR dongle, and has already been tested to work.

A typical 1-seg capable Japanese mobile phone receiving digital mobile TV.
A typical 1-seg capable Japanese mobile phone receiving digital mobile TV. With the GNU Radio 1-seg decoder these transmissions can be received with an RTL-SDR.

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