QAM scan does not find all channels

[sihde@…]

I'm using QAM with Comcast in San Francisco. I was using channels.conf import before but now I'm trying the Myth scan.

With the signal timeout at the default of 500ms, virtually nothing was found, just a bunch of music programming on 127. After increasing the timeout to 3000ms, lots of stuff is found, including many of the channels I'm interested in. However, Comcast also carries all the local channels in standard-definition digital on channel 93. The scan doesn't find any of them. Increasing the timeout to 6000ms doesn't seem to make any difference.

I'm attaching a log of "mythtv-setup -v siparser,record,channel" and a also a bit of a dump from dvbsnoop with the card tuned to channel 93 (this shows that there are indeed a bunch of channels on 93). The interesting thing is Myth does see SOME channels on 93 -- it gets 93_6 and 93_8 -- but 93_{1,2,3,4,5,7} are also just fine and happen to have all the major network programming in SD.

For examples where the scan seemed to work well (including finding callsigns, though they don't match Zap2It's callsigns), see channels 111, 113, and 114.

Please let me know if I can provide any more information.

Thanks, Steve

[anonymous]

mythtv-setup log

[steve@…]

Turns out it did find all the channels.

The source of my confusion is that atscscan and MythTV seem to use different channel numbering schemes -- what atscscan calls channel 93, MythTV calls 95. Here's an except from dvb-apps/util/scan/atsc/us-Cable-Standard-center-frequencies-QAM256:

#90 A 621000000 QAM256 A 627000000 QAM256 A 633000000 QAM256 A 639000000 QAM256 A 645000000 QAM256 A 93000000 QAM256 A 99000000 QAM256 A 105000000 QAM256 A 111025000 QAM256 A 117025000 QAM256 #100 A 651000000 QAM256

MythTV seems to call 639MHz channel 95.

Thanks,

Steve

[danielk]

(In [10231]) Refs #1779. Refs #1935. Increases signal timeout for AverMedia? 180 from 500 ms to 3000 ms (for more reliable channel scan).