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In dvb:

the receiver has to know which frequency the new transport stream is being broadcast on (and this alone is not trivial). Second, the receiver has to tell the tuner to change to the new frequency.

My question is how the receiver knows which frequency the new transport stream is being broadcast, i mean given a range of frequency (min_freq, max_freq),how the receiver knows the good frequency, what is the mechanism behind.

Mouin
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2 Answers2

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Each change in DVB is signaled by table version change.
If new transport stream is being broadcast, then new NIT version must be signaled as well.
In NIT table there is a 2nd description loop, in which you can find list of all transport streams in the network. In this loop there are as well descriptors that tells you on which frequency there is each transport stream broadcast.
See delivery_descriptor in NIT table for new added transport stream.

Przemo
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  • thank u for the feedback "NIT version must be signaled as wel" NIT are optional see [this](https://abacus.abo.fi/ro.nsf/141b8735bd22ff31c225700600473a01/dd23352b9f91b46bc22576ef00213656/$FILE/lect4.pdf)page 20, "See delivery_descriptor in NIT table" could u please give us reference – Mouin Dec 05 '16 at 11:04
  • NIT table according to MPEG standard is optional. But MPEG standard cannot give you information about Networks. About many other information that are needed for modern digital television receivers. Thus DVB standard was crated and according to it the NIT table is mandatory. See ETSI EN 300 468, 6.2.13 (delivery system descriptors). – Przemo Dec 05 '16 at 14:34
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Przemo's hint to the NIT is correct. It is defined in ETSI EN 300 468. That document will also tell you about the delivery system descriptors in the NIT.