DVB-T scan: muxes not tuned during full scan but tuned using NIT info

[Nick Morrott <knowledgejunkie (at) gmail (dot) com>]

Using the same configuration as reported in #8726.

Scan details: full UK scan using Sutton Coldfield transmitter with 6 available muxes. Signal/tuning timeouts raised to 2000/6000ms. ALL services (DVB+MPEG) scanned, with decryption testing disabled.

During the scan, a signal and successful lock is achieved on only 1 of the possible muxes (746000000), even when using doubled timeouts. The remaining 5 muxes are discovered in the NIT of this mux, and subsequent tuning of these muxes is successful.

Checking the log output reveals the following for sample mux 634166670:

i) During the initial full scan using default scan parameters, the following was seen:

                        DVBChan(1:/dev/dvb/adapter102/frontend0): New Params: 634166670 auto 0 auto auto 8 a 1/32 n v fec: auto msys: UNDEFINED rolloff: 0.35
2010-08-05 06:42:04.455 DVBChan(1:/dev/dvb/adapter102/frontend0): Tune(): Frequency tuning successful.
2010-08-05 06:42:04.455 DTVSM(/dev/dvb/adapter102/frontend0)::SetChannel(-1, -1):
2010-08-05 06:42:04.455 SM(/dev/dvb/adapter102/frontend0)::Start: begin
2010-08-05 06:42:04.455 SM(/dev/dvb/adapter102/frontend0)::Start: end
2010-08-05 06:42:04.504 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:04.504 SM(/dev/dvb/adapter102/frontend0)::RemoveFlags: Seen() Match() Wait(Pos,)
2010-08-05 06:42:04.566 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:04.628 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:04.690 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:04.752 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:04.814 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:04.876 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:04.937 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:05.893 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:05.955 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:06.017 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:06.079 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:06.141 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:06.203 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:06.264 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:06.326 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:06.388 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:42:06.449 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)

No signal is seen within the 2000ms timeout value

ii) Having extracted this sample mux's details from the NIT of the 1 mux locked to (746000000), the later "fill-in" scan was succesful:

                        DVBChan(1:/dev/dvb/adapter102/frontend0): New Params: 634166670 qam_16 a 3/4 3/4 8 2 1/32 n v fec: auto msys: UNDEFINED rolloff: 0.35
2010-08-05 06:45:51.455 DVBChan(1:/dev/dvb/adapter102/frontend0): Tune(): Tuning to 634166670Hz
2010-08-05 06:45:52.356 dvbchannel.cpp:wait_for_backend: Status:
2010-08-05 06:45:52.356 DVBChan(1:/dev/dvb/adapter102/frontend0): Tune(): Frequency tuning successful.
2010-08-05 06:45:52.356 DTVSM(/dev/dvb/adapter102/frontend0)::SetChannel(-1, -1):
2010-08-05 06:45:52.356 SM(/dev/dvb/adapter102/frontend0)::Start: begin
2010-08-05 06:45:52.356 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:45:52.356 SM(/dev/dvb/adapter102/frontend0)::Start: end
2010-08-05 06:45:52.356 SM(/dev/dvb/adapter102/frontend0)::RemoveFlags: Seen() Match() Wait(Pos,)
2010-08-05 06:45:52.420 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:45:52.481 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen() Match() Wait(Sig,)
2010-08-05 06:45:52.510 DVBSM(/dev/dvb/adapter102/frontend0): UpdateValues -- Signal Locked
2010-08-05 06:45:52.540 SM(/dev/dvb/adapter102/frontend0)::AddFlags: Seen(PAT,) Match() Wait()
2010-08-05 06:45:52.540 ChannelScanSM(/dev/dvb/adapter102/frontend0): Got a Program Association Table for TransportID 4101

Is it possible to modify the default scan parameters in order to increase the likelihood of finding more/all muxes during the initial scan?

Full log output of the scan is attached.

[Nick Morrott <knowledgejunkie (at) gmail (dot) com>]

DVB-T, UK, Full scan

[dekarl@…]

Comparing both sets of tuning parameters suggests that the auto detection of one of the parameters does not work.

DVBChan(1:/dev/dvb/adapter102/frontend0): New Params: 634166670   auto 0 auto auto 8 a 1/32 n v fec: auto msys: UNDEFINED rolloff: 0.35
DVBChan(1:/dev/dvb/adapter102/frontend0): New Params: 634166670 qam_16 a  3/4  3/4 8 2 1/32 n v fec: auto msys: UNDEFINED rolloff: 0.35

The proper fix involves querying the driver's/device's capabilities and try all combinations of parameters where autodetection is not supported.

[Klaas de Waal]

Nick, is there still a problem when you make a scan with the current pre-v31 master?

[Klaas de Waal]

There have been many improvements in the channel scanning and this ticket is very old. Assuming that the problem is solved in v31 this ticket is now closed. If the problem appears again please re-open this ticket or create a new one.