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QAM Comcast in San Francisco -- Tuning failed
PostPosted: Mon Mar 20, 2006 1:20 pm Reply with quote
steve
 
Joined: 20 Mar 2006
Posts: 5
Location: San Francisco




I'm trying to tune channels directly off my Comcast cable in San Francisco (i.e., not through the STB). I just get "tuning failed" for every single channel -- not one seems to come through. After no success with MythTV, I tried atscscan from the latest dvb-apps, and found the same result. I tried all the scan files that seemed related to cable:

us-Cable-Standard-center-frequencies-QAM256
us-Cable-IRC-center-frequencies-QAM256
us-Cable-HRC-center-frequencies-QAM256
us-Cable-EIA-542-IRC-center_frequencies-QAM256
us-Cable-EIA-542-HRC-center-frequencies-QAM256

And got nothing from any of them. The only thing that seemed to go right was I did see a log message that it was uploading the "qam" firware (instead of the vsb firmware) to the HD-3000, and that seemed to work.

Has anyone done this successfully?

A few more questions:

Is it true I should be able to pick up the local ATSC channels in HD, even if I don't specifically have an HD subscription from Comcast?

How can I pick up existing SD analog channels with the HD-3000? Can this be done using the DVB driver (if so, how) or do I have to use the V4L driver?

Are only the digital channels "QAM" or does "QAM" cover the analog channels too?

BTW, I did find a similarly-named thread about Comcast in Seattle, but from reading the thread it didn't sound like the issue ever got resolved.

Thanks,

Steve
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PostPosted: Mon Mar 20, 2006 11:46 pm Reply with quote
steve
 
Joined: 20 Mar 2006
Posts: 5
Location: San Francisco




After supplying the "-A 2" argument to atscscan, I had slightly better luck. It still seems to print "tuning failed" for nearly every single channel, and a bunch of messages about timeouts. But it does produce a config file with 357 lines like so:

Code:

[000c]:531000000:QAM_256:0:2049:12
[0005]:531000000:QAM_256:0:2113:5
[0008]:531000000:QAM_256:0:2177:8
[0004]:531000000:QAM_256:0:2305:4
[0009]:531000000:QAM_256:0:2369:9
[0007]:531000000:QAM_256:0:2433:7
[000f]:531000000:QAM_256:0:2497:15
[0001]:531000000:QAM_256:0:2561:1
[000d]:531000000:QAM_256:2624:2625:13


and so on. In no case does the first column have an intelligible station identifier such as "KQED-DT" like I've seen in other example files -- they're all just hex numbers like [0035], etc.

When executing "azap -r [0002]", it does claim to tune the channel -- I get the FE_HAS_LOCK messages. But if I

Code:

cat /dev/dvb/adapter0/dvr0 > /tmp/test.mpg


then this yields a plausibly large file, but xine won't play it. Xine had no problem playing files captured OTA using my antenna.

Any clue what I'm doing wrong?

Something else is confusing me. When I look at the channel listings in http://www.avsforum.com/avs-vb/showthread.php?t=357896, all the comcast channels it mentions are over 700. But looking at the us-Cable-Standard-center-frequencies-QAM256 file, it only seems to go up to about 120. Am I missing something?

Thanks,

Steve
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PostPosted: Wed Mar 22, 2006 11:53 am Reply with quote
kregars
 
Joined: 03 Mar 2006
Posts: 8
Location: Waldorf MD/DC Metro




I am having the same issue, but there is hope. CATV systems can put multiple carriers on a single frequency. I have found 2 things thus far with Comcast...1) their signals appear to be low on the SNR side. This is detected with a meter...for instance...I have 18dB for my cable modem range (keep in mind that anything below 25dB will have severe packet loss)....but on the video portion I am showing ~22dB steady. I have replaced the Comcast supplied splitter off the RG11 with one that does 2.4ghz as opposed to just 800mhz...that cleaned it up some...standing at 24dB (and modems SNR jumped to 22dB)....good...but not perfect. I then looked at the RG11 cable and SNS connector...it looked 'weathered'...so ...SNIP and SNAP but alas..not much better....looked at the cable from the RG11 handoff to my inside wiring (why they didnt run RG11 INTO the house for the drop to have a weather tight/safe connection boggles the mind)....I found there was a splitter inside the wall (bought the house last year) that was REALLY old...went to RS and bought a new one to test to see if this cleaned anything up....walla...it did.

Also I found that my PSU albeit a 2.0 compliant PS was a POS...I moved the pcHDTV card to the bottom slot (furthest from the PSU) to get away from any errant signal that may be emminating from there...signal strenth actually went down a bit, but I think it MAY have been picking up some bleedover from there...but now I can lock on the channels, however, I am not getting the channel header info (station call sign) so I have to walk through the 47 [<blah>] in the channels.conf to find out what is real and what is WRONG.

It's a long road to success, but it starts at the cable being fed to you by your cable company (no matter who it might be...in my (and your) case it is Comcast). If the cables fine outside, start looking inside.

BTW...all my local HD channels start at Channel 201-210 (locals). YMMV.
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PostPosted: Wed Mar 22, 2006 2:24 pm Reply with quote
steve
 
Joined: 20 Mar 2006
Posts: 5
Location: San Francisco




Thanks for replying.

Actually I think my problems are related not to signal strength but just understanding this whole Comcast thing. I was able to tune a few stations last night, and feel like I'm well on the way to a solution.

The big problem seems to be that Comcast strips all the PSIP information from the stream. So no station callsigns, etc., are available. This leads to numerous issues.

1. MythTV. MythTV's channel scan simply won't work at all without the PSIP data. This appears to be a well-known issue.

2. "Tuning failed" messages. It took me a while to realize that because the cable company uses channels 2-73 (approx.) for analog broadcasts, there will be nothing in the first 70 channels when using, e.g., us-Cable-Standard-QAM256 as the input file. It also seems to generate these messages even when it is finding services, I don't understand why.

3. Cryptic "Channels.conf" generated. As you noted, the generated channel names don't have any intelligible information in the channel name, just hex digits like "[001c]" and such. My scan actually dumped over 370 services -- don't really want to sort through that many. Looking closely, many of those services are audio-only (presumably the digital music channels) or "other". There are over 100 that have both an audio and video stream. But of course, many (probably most) of those are encrypted and can't be viewed. So far I only found one that really works, KNTV, the NBC affiliate in San Jose.

But, now I have hope. I'm working on a script that will scan through to find only the unencrypted, video+audio services.

This thread seems to have info on how to get all this stuff into MythTV, and links to a couple other good threads.

http://www.pchdtv.com/forum/viewtopic.php?p=5656

But it looks to be a pretty painful process. This page on the MythTV wiki also has info.

http://www.mythtv.org/wiki/index.php/Adding_QAM_Channels_For_HDTV_Tuner_Cards
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PostPosted: Wed Mar 22, 2006 2:29 pm Reply with quote
steve
 
Joined: 20 Mar 2006
Posts: 5
Location: San Francisco




kregars wrote:

BTW...all my local HD channels start at Channel 201-210 (locals). YMMV.


One question about that.... as far as I can tell all the cable data files only go up to channel 125 (approx.). There are multiple substreams within each digital channel of course -- channel 70-1, 70-2, etc. But the highest channel number must be something like 125-something, so channel numbers like 201 through 210 must be mapped using the PSIP data -- and you're not getting the PSIP data, right? So how can you be using channel numbers like 201? Or are you just saying that's where they appear when you use your set-top box? (Presumably the set-top box has access to the mapped channel numbers.)

Thanks,

Steve
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PostPosted: Wed Mar 22, 2006 4:06 pm Reply with quote
kregars
 
Joined: 03 Mar 2006
Posts: 8
Location: Waldorf MD/DC Metro




The channel assignements are in essence 'virtual' channels. Since the limitation of actual channels avail is limited by the market tuners. If you have been in an area that used to have tiered services, you remember the 2 cables that came into the house and plugged into the receiver. There were 2 receivers in the box and an internal A/B switcher and a link cable that noted when channel 124 was reached to activate the switch to flip to the B sid and hit channel 2 again (202)..(think old Zenith CATV receivers).

In any case..to better answer your question. There are infact multiple video and audio sub channels within a given frequency. They are sub carrier and are differientiated by PSIP that is statically mapped by the upstream provider (comcast).

In your example for instance, you are seeing:
[000d]:531000000:QAM_256:2624:2625:13

with the video and audio on 'channels' 2624 and 2625 respecively...thus assuming this isnt encrypted, you should have audio and video.
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QAM comcast San Francisco
PostPosted: Fri Mar 24, 2006 6:07 pm Reply with quote
cjlemmon
 
Joined: 05 Mar 2006
Posts: 2
Location: San Francisco




i'm in SF as well working on the same thing. the alphanumeric characters between the brackets [] are the serviceid in hexadecimal. Notice the last value in the line is the decimal value for the service id. Here are some channels that I gleamed from trying to tune them all.

Note: I named the channels
Code:
FAMILY:597000000:QAM_256:2241:2240:1
DISNEY:597000000:QAM_256:2561:2560:6
TVGUIDE:615000000:QAM_256:2048:2049:1
FOX2:639000000:QAM_256:2048:2049:1
KRON4:639000000:QAM_256:2112:2114:2
CBS:639000000:QAM_256:2176:2178:3
ABC:639000000:QAM_256:2240:2242:4
KQED:639000000:QAM_256:2304:2305:5
COMEDY:639000000:QAM_256:2624:2625:10
LIFE:651000000:QAM_256:2752:2753:5
CSPAN:651000000:QAM_256:2176:2177:1
CSPAN2:651000000:QAM_256:2240:2241:2


I am also using mythtv. With the hd3000 tuner I'm getting around 40 channels. last night I watched and recorded the college basketball tournament. The picture was beautiful High Definition.

Should i be trying to tune more channels? Zap2it says there are 100 or more channels out there. I'm getting all the KQED digital channels, movieplex, the national broadcast channels, disney, family and some others. Are all the rest encrypted?
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PostPosted: Sat Apr 01, 2006 12:00 am Reply with quote
atomjack
 
Joined: 04 Aug 2005
Posts: 4




I too am having problems with this. I live in San Francisco as well. The thing is, for the past year or so I've been able to get a lot of HD channels. For awhile I was even able to tune InHD, InHD2, and DiscoveryHD until they started encrypting them.

Just a few days ago though, most of my HD channels just stopped tuning in on my mythtv. I'm still able to tune in and record fox and cbs, but nbc, abc, and all the kqed(pbs) stations don't come in at all anymore. Also, most of these stations stopped coming in when trying to use the regular tuner on my HDTV - I had to have it to a rescan, and now the channels all come in but on different channel numbers from before. Before, I'd get fox on 2.1, nbc on 11.3, cbs on 5.1, and abc on 7.1 (where sd came in on 2, 3, 5, and 7 respectively - I don't know why the 3/11.1 but..there it is). Now, the stations come in on channels like 113.x and 117.x or something like that. But, they come in.

The QAM frequencies for CBS and Fox have not changed, so I am still able to tune those in, but all the rest I have don't come in.

One thing I've noticed is that for the frequencies that don't work anymore, when I use dvbtraffic after scanning them in with azap, dvbtraffic reports a whole shitload of really low bandwidth results, and no lock, whereas for the channels that do work (and the ones that used to work), I'd get a small number of high bandwidth results, corresponding to the actual HD stations (I think no more than 2 true HD channels per frequency, with them cramming some of the digital SD channels on the same frequency, but those use up a lot less bandwidth.)

So, now I can only tune in two HD stations on myth, even though my tv is able to tune in all the major networks, plus the pbs station, and now it looks like a whole bunch of SD stations are being shown digitally.

Here's the only two HD channels and their frequency/pid's that I am able to tune in with my hd-3000 card (works in and out of myth):
KTVU:735000000:QAM_256:2112:2113
KPIX:735000000:QAM_256:2048:2049

Anyone have any ideas? I am tempted to call comcast up and ask them if they know what the deal is...I don't think it could get much worse by asking them...although I'm sure I'd get some clueless support rep.
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PostPosted: Sat Apr 01, 2006 8:48 am Reply with quote
kregars
 
Joined: 03 Mar 2006
Posts: 8
Location: Waldorf MD/DC Metro




Most likely they just reorganized the channel lineup. They did that here in Southern MD a few months ago...before the local HD channels were dithered around their SD counterparts, but now they start at 209 and go to 222. I also lost DiscoveryHD, but gained InHD1/2 as well as I found that I can grab the PPV stream...but only when someone on my node orders a PPV...guessing they either removed a filter from my block, or forgot to put one in...in any case...whoever is ordering movies orders some of the worst ones on PPV. Smile
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PostPosted: Sat Apr 01, 2006 1:10 pm Reply with quote
atomjack
 
Joined: 04 Aug 2005
Posts: 4




Ok, I guess I spoke too soon. As of this morning all the major networks are tuning in now, including KQED.. Weird
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QAM Comcast in San Francisco -- Tuning failed
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