Interesting: someone who mailed me about ... / 2011-06-19

2011-06-19 Interesting: someone who mailed me about ... 8 years ago
Interesting: someone who mailed me about my dvb experiments and noted a frequency picked up by the scanning program which I didn't recognize as a valid multiplex: 714 MHz, 2/3 fec, 1/16 guard interval. That's odd, that frequency isn't in use in the Netherlands and no multiplex runs on 1/16 guard interval.

When I have a look at the details for Digitenne at DTV Monitor and I open the network information table in transport stream 2211 or 2212 I see a listing for a transport stream 12 with indeed guard interval 1/16 and 2/3 fec. Weird. Yet another multiplex in the planning or a glitch? But a glitch showing up on multiple transport streams in multiple locations is more like 'planned'.

To make sure I checked the Network Information Table in Mux 1 at home myself, with dvbsnoop for pid 0x10. Indeed, a description of transport stream 12 with 5 television services flies by:
    Transport_stream_ID: 12 (0x000c)
    Original_network_ID: 8720 (0x2210)  [= Netherlands Digital Terrestrial Television | Nozema]
    reserved_1: 15 (0x0f)
    Transport_descriptor_length: 52 (0x0034)

            DVB-DescriptorTag: 65 (0x41)  [= service_list_descriptor]
            descriptor_length: 15 (0x0f)
               service_ID: 1201 (0x04b1)[ --> refers to PMT program_number]
               service_type: 1 (0x01)  [= digital television service]

               service_ID: 1202 (0x04b2)[ --> refers to PMT program_number]
               service_type: 1 (0x01)  [= digital television service]

               service_ID: 1203 (0x04b3)[ --> refers to PMT program_number]
               service_type: 1 (0x01)  [= digital television service]

               service_ID: 1205 (0x04b5)[ --> refers to PMT program_number]
               service_type: 1 (0x01)  [= digital television service]

               service_ID: 1206 (0x04b6)[ --> refers to PMT program_number]
               service_type: 1 (0x01)  [= digital television service]


            DVB-DescriptorTag: 90 (0x5a)  [= terrestrial_delivery_system_descriptor]
            descriptor_length: 11 (0x0b)
            Center frequency: 0x04417a40 (= 714000.000 kHz)
            Bandwidth: 0 (0x00)  [= 8 MHz]
            priority: 1 (0x01)  [= HP (high priority) or Non-hierarch.]
            Time_Slicing_indicator: 1 (0x01)  [= Time Slicing is not used.)]
            MPE-FEC_indicator: 1 (0x01)  [= MPE-FEC is not used.)]
            reserved_1: 3 (0x03)
            Constellation: 2 (0x02)  [= 64-QAM]
            Hierarchy information: 0 (0x00)  [= non-hierarchical (native interleaver)]
            Code_rate_HP_stream: 1 (0x01)  [= 2/3]
            Code_rate_LP_stream: 0 (0x00)  [= 1/2]
            Guard_interval: 1 (0x01)  [= 1/16]
            Transmission_mode: 1 (0x01)  [= 8k mode]
            Other_frequency_flag: 0 (0x00)
            reserved_2: 4294967295 (0xffffffff)

            DVB-DescriptorTag: 131 (0x83)  [= User defined/ATSC reserved]
            descriptor_length: 20 (0x14)
            Descriptor-data:
                 0000:  04 b1 fd f5 04 b2 fd f6  04 b3 fd f7 04 b5 fd f8   ................
                 0010:  04 b6 fd f9                                        ....

So an extra transport stream with 5 video services is announced, but not in use. Future plans? A reservation? Something left over from a test?

Note: dvbsnoop does not decode the Logical Channel Descriptor (0x83) at the end of the network information table. According to dtv monitor, services 1201 - 1205 are to be on logical channels 501 - 505.

Kudos to the person who noticed his scanning program searching on an unused frequency.

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