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Can't receive digital or analog signals
PostPosted: Sun Oct 07, 2007 11:39 am Reply with quote
slamb
 
Joined: 07 Oct 2007
Posts: 3




I'm a Comcast digital cable in Mountain View, CA. When I plug the cable directly into my television (i.e., no computer or cable box), I see (among others) 1080i on channel 5-1, 720p on channel 4-2, and analog on channel 3.

When I plug the cable directly into my new pcHDTV HD-5500, I can't get these or any other channels to display. I've tried kernel versions 2.6.18-8.1.8.el5 (came with CentOS 5) and 2.6.22.9, which I compiled last night. In both cases, I've downloaded and installed the newest hg version of the v4l-dvb drivers and loaded them, seemingly successfully. dmesg output looks good to my eyes (can post it if desired). Also tried the 5/22/06 version available at http://pchdtv.com/.

Digital: With cx88-dvr loaded and using dvb-atsc-tools-1.0.7, "dtvsnr N" (for N in 3, 4, 5) displays "NO LOCK"; "dtvsignal N" says "Signal: 000". "dtvscan" appears to find nothing. Tried the "-q" argument on each tool. Also tried the linuxtv-dvb-apps-1.1.1 package I found elsewhere. Had high hopes for "util/scan/scan -q util/scan/atsc/us-CA-SF-Bay-Area"...but it reported tuning failed on all channels.

Analog: "mplayer tv:// -tv driver=v4l2:chanlist=us-cable:channel=3" (as I gather analog TV should be watched; this same command worked with an ancient, cheap bttv card) displays nothing but snow. It also complains on console a couple times: "v4l2: ioctl set format failed: Invalid argument". It definitely recognized the device as a "pcHDTV HD5500 HDTV", though.

Any ideas? I don't see any other way to test, so I'm getting close to sending the card back as defective.
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PostPosted: Sun Oct 07, 2007 2:31 pm Reply with quote
jason52
 
Joined: 06 Oct 2007
Posts: 17




Don't know if you already tried it, but with either of those kernels (I think, definitely in the 2.6.22), you ought to be able to just modprobe cx88-dvb and have everything installed for you - can't tell if you have all the modules loading or not. I'm running a 2.6.20 kernel and didn't have to install any new drivers.

As far as tuning digital channels, you'll have to figure out how Comcast remaps them. For instance, 6.1 here is broadcast by Cox on channel 111. Although dtvscan should help with that. Signal strength seems to be a big issue - I gave up on tuning the QAM from my cable since I have one too many splitters in my house. And I'm too lazy to get up in the crawl space to string some new coax.
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PostPosted: Sun Oct 07, 2007 2:45 pm Reply with quote
slamb
 
Joined: 07 Oct 2007
Posts: 3




jason52 wrote:
Don't know if you already tried it, but with either of those kernels (I think, definitely in the 2.6.22), you ought to be able to just modprobe cx88-dvb and have everything installed for you - can't tell if you have all the modules loading or not. I'm running a 2.6.20 kernel and didn't have to install any new drivers.


Okay, I'll give the in-tree driver a shot.

Quote:
As far as tuning digital channels, you'll have to figure out how Comcast remaps them. For instance, 6.1 here is broadcast by Cox on channel 111. Although dtvscan should help with that.


What does your television say the channel number is? I saw something on wikipedia about virtual channel numbers, but have been assuming that neither my TV nor my computer would pay any attention to them - channel numbers should be the same both places.

In any case, the dtvscan showed nothing. I have not been able to get my computer to behave any differently when the cable is or is not plugged in.

Quote:
Signal strength seems to be a big issue - I gave up on tuning the QAM from my cable since I have one too many splitters in my house. And I'm too lazy to get up in the crawl space to string some new coax.


I live in an apartment building, and there's only one splitter under my control - needed for my cable modem. My television reports excellent signal strength.
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PostPosted: Sun Oct 07, 2007 6:19 pm Reply with quote
xyzzy
 
Joined: 12 Feb 2006
Posts: 225




Your TV is re-mapping the digital channels using information from the PSIP. Your channel 5-1 is probably on channel 100 something. Try my http://www.speakeasy.org/~xyzzy/download/atscscan program to look for channels.

mplayer can be tricky to use. I know you need to specify norm=NTSC-M to get it to work. You might also have version of mplayer that doesn't work for other reasons. I suggest installing tvtime and using that to test analog. It's a lot nicer for watching analog tv than mplayer.
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Re: Can't receive digital or analog signals
PostPosted: Sun Oct 07, 2007 6:50 pm Reply with quote
waterhead
 
Joined: 24 Apr 2005
Posts: 299




slamb wrote:
I've tried kernel versions 2.6.18-8.1.8.el5 (came with CentOS 5) and 2.6.22.9, which I compiled last night.


I'm using CentOS with MythTV and my HD-3000. I found that the CentOS kernel is not compiled with support for any DVB modules.

I downloaded new kernel sources of the 2.6.18 kernel and used the config file from a Suse install that used the exact same kernel. I'm too lazy to go through the entire config file to find what else was missing.

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PostPosted: Mon Oct 08, 2007 1:48 am Reply with quote
slamb
 
Joined: 07 Oct 2007
Posts: 3




xyzzy wrote:
Your TV is re-mapping the digital channels using information from the PSIP. Your channel 5-1 is probably on channel 100 something. Try my http://www.speakeasy.org/~xyzzy/download/atscscan program to look for channels.


Success! I think I was confused by dcb-atsc-tools-1.0.7's scan output, or I didn't let it complete a full scan (thought I had). In any case, atscscan found a lot of channels, and some of them work when fed into mplayer.

Quote:
mplayer can be tricky to use. I know you need to specify norm=NTSC-M to get it to work. You might also have version of mplayer that doesn't work for other reasons. I suggest installing tvtime and using that to test analog. It's a lot nicer for watching analog tv than mplayer.


Aha! norm=NTSC-M made the difference. Analog channels work now. Though I am disappointed in the video quality - it is not as good as when feeding directly into the television. I was also under the impression this card had a hardware MPEG encoder, but it appears not.

tvtime looks unmaintained - is this http://tvtime.sourceforge.net/? Last release in 2005, doesn't build cleanly. Is there a newer version elsewhere?
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Can't receive digital or analog signals
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