Em Sat, 25 Nov 2017 18:50:28 +0100 Gregor Jasny <gjasny@xxxxxxxxxxxxxx> escreveu: > Hello, > > I found the culprit why dvbv5-scan only find some of the channels in my > DVB-T2 region: Some broadcasted NIT tables announce the 578MHz channel > transmission mode as 16k where it should be 32k. Ah! Yeah, it is hard for it to work properly when the MPEG tables are wrong :-) > The tables at 578MHz > look ok, but that does not help with discovery. > > Long story: > > I have the following initial scan file: > > T2 538000000 8MHz AUTO NONE AUTO 32k 1/16 NONE > T2 642000000 8MHz AUTO NONE AUTO 32k 1/16 NONE 1 > T2 618000000 8MHz AUTO NONE AUTO 32k 19/256 NONE > T2 754000000 8MHz AUTO NONE AUTO 16k 19/128 NONE > T2 578000000 8MHz AUTO NONE AUTO 32k 19/256 NONE > > The last line was added manually because even w_scan gets confused. > > > Scanning frequency #1 538000000 > > Lock (0x1f) C/N= 21.50dB UCB= 3790 postBER= 166x10^-3 > > Service SAT.1 HD, provider ProSiebenSat.1 Media: reserved > > Service ProSieben HD, provider ProSiebenSat.1 Media: reserved > > Service kabel eins HD, provider ProSiebenSat.1 Media: reserved > > Service SIXX HD, provider ProSiebenSat.1 Media: reserved > > Service Pro7 MAXX HD, provider ProSiebenSat.1 Media: reserved > > Service SAT.1 Gold HD, provider ProSiebenSat.1 Media: reserved > > Service Sport1 HD, provider ProSiebenSat.1 Media: reserved > > New transponder/channel found: #6: 578000000 > > New transponder/channel found: #7: 522000000 > > New transponder/channel found: #8: 658000000 > > New transponder/channel found: #9: 626000000 > > New transponder/channel found: #10: 602000000 > > New transponder/channel found: #11: 586000000 > > New transponder/channel found: #12: 698000000 > > New transponder/channel found: #13: 554000000 > > New transponder/channel found: #14: 498000000 > > New transponder/channel found: #15: 650000000 > > New transponder/channel found: #16: 738000000 > > New transponder/channel found: #17: 690000000 > > New transponder/channel found: #18: 594000000 > > New transponder/channel found: #19: 778000000 > > New transponder/channel found: #20: 666000000 > > New transponder/channel found: #21: 498000000 > > Scanning frequency #2 642000000 > > Scanning #5 (from manually added table works): > > > Scanning frequency #5 578000000 > > FREQUENCY = 578000000 > > MODULATION = QAM/AUTO > > BANDWIDTH_HZ = 8000000 > > INVERSION = AUTO > > CODE_RATE_HP = AUTO > > CODE_RATE_LP = NONE > > GUARD_INTERVAL = 19/256 > > TRANSMISSION_MODE = 32K > > HIERARCHY = NONE > > STREAM_ID = 4294967295 > > DELIVERY_SYSTEM = DVBT2 > > Carrier(0x03) Signal= -54.00dBm > > Got parameters for DVBT2: > > FREQUENCY = 578000000 > > MODULATION = QAM/AUTO > > BANDWIDTH_HZ = 8000000 > > INVERSION = AUTO > > CODE_RATE_HP = AUTO > > CODE_RATE_LP = AUTO > > GUARD_INTERVAL = 19/256 > > TRANSMISSION_MODE = 32K > > HIERARCHY = NONE > > STREAM_ID = 4294967295 > > Scanning #6 (detected at #1) fails: > > > Scanning frequency #6 578000000 > > FREQUENCY = 578000000 > > MODULATION = QAM/AUTO > > BANDWIDTH_HZ = 8000000 > > INVERSION = AUTO > > CODE_RATE_HP = AUTO > > CODE_RATE_LP = NONE > > GUARD_INTERVAL = 19/128 > > TRANSMISSION_MODE = 16K > > HIERARCHY = NONE > > STREAM_ID = 1 > > DELIVERY_SYSTEM = DVBT2 > > Carrier(0x03) Signal= -47.00dBm > > Is there anything that could / should be done at dvbv5-scan side? Maybe > re-trying a frequency with different parameters if tuning failed? Well, deep scan software (like w_scan) can read the device's capabilities and, for all parameters that aren't auto-detected, try all possible combinations when a channel is not found. The problem is that, while a normal channel scan lasts a couple of minutes, a deep scan can take several hours. There is one additional issue: we didn't add all possible capabilities that are present on modern DTV standards. The rationale is simple: we would need additional bits, as we're almost out of capabilities bits with the current API. So, a complete solution would very likely require DVB core, DVB driver and libv4l5 changes. -- Thanks, Mauro
