On Sat, Nov 28, 2009 at 10:22 AM, Dale Pontius <[email protected]> wrote: > Well it is Comcast, after all... More of which will become evident > shortly. I can't receive any channels adequately over QAM. Either the > channel is encrypted, apparently with adequate signal strength, or it's > clear with poor signal strength. Here are some results from azap: > > u...@localhost ~/computers/hdtv $ azap CH567-1 > using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0' > tuning to 567000000 Hz > video pid 0x07c0, audio pid 0x07c1 > status 00 | signal 0000 | snr 0000 | ber 00000000 | unc 00000000 | > status 07 | signal 013a | snr 013c | ber 00001c2f | unc 00001c2f | > status 00 | signal 0142 | snr 0142 | ber 000032b9 | unc 000032b9 | > status 00 | signal 0000 | snr 0000 | ber 00000000 | unc 00000000 | > status 00 | signal 0145 | snr 0145 | ber 00000b0d | unc 00000b0d | > status 00 | signal 0145 | snr 0145 | ber 000032ce | unc 000032ce | > status 1f | signal 0145 | snr 0145 | ber 00001be0 | unc 00001be0 | FE_HAS_LOCK > status 1f | signal 013e | snr 013e | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 00 | signal 0000 | snr 0000 | ber 00000000 | unc 00000000 | > status 00 | signal 0145 | snr 0146 | ber 00000bce | unc 00000bce | > status 00 | signal 0000 | snr 0000 | ber 00000000 | unc 00000000 | > status 07 | signal 0140 | snr 0140 | ber 00001aa0 | unc 00001aa0 | > status 00 | signal 0140 | snr 0140 | ber 000032ca | unc 000032ca | > status 1f | signal 0142 | snr 0142 | ber 00001c04 | unc 00001c04 | FE_HAS_LOCK > status 18 | signal 013c | snr 013c | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 00 | signal 0000 | snr 0000 | ber 00000000 | unc 00000000 | > status 00 | signal 0145 | snr 0145 | ber 00000c0b | unc 00000c0b | > ^C > > That was a clear channel, here's an encrypted one: > > u...@localhost ~/computers/hdtv $ azap CH561-1 > using '/dev/dvb/adapter0/frontend0' and '/dev/dvb/adapter0/demux0' > tuning to 561000000 Hz > video pid 0x0000, audio pid 0x0f42 > status 00 | signal 0000 | snr 0000 | ber 00000000 | unc 00000000 | > status 1f | signal 013c | snr 013e | ber 00001c0c | unc 00001c0c | FE_HAS_LOCK > status 1f | signal 0148 | snr 0148 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0148 | snr 0148 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0148 | snr 0148 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0146 | snr 0146 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0146 | snr 0146 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0148 | snr 0148 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0148 | snr 0148 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0148 | snr 0148 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0146 | snr 0146 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0148 | snr 0148 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0148 | snr 0148 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0148 | snr 0148 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0148 | snr 0148 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > status 1f | signal 0146 | snr 0146 | ber 00000000 | unc 00000000 | FE_HAS_LOCK > ^C
If you haven't already, you should install the latest v4l-dvb code. I did some fixes which significantly improve the signal quality for ClearQAM tuning. > These are only 2 channels, but everything else is like this - encrypted > channels get a solid lock, clear ones done. It is very common for a cable provider to multiplex *all* the ClearQAM channels onto two or three frequencies. So you shouldn't expect to see ten or twelve unencrypted frequencies just because there are ten or twelve "must-carry" ClearQAM channels. > So to boil this down to a question: How do I interpret the results of > azap? If I try searching, all I get is people talking about using it > to look for "FE_HAS_LOCK". I find nothing about how to interpret the > various fields, for instance "status", "signal", "snr", "ber", "unc". > It's kind of obvious what "signal" and "snr" mean, but not how to > interpret the hex numbers presented. It equally seems like an obvious > guess that for signal and snr the bigger the better, but in some cases > I have seen clear channels have decent numbers, as high as 014a, but > not sticking there, and still not getting a decent lock. The SNR and strength values vary in terms of how they are interpreted, which is why everybody says that you can only rely on the FE_HAS_LOCK field across different products. For your product, both the SNR and strength field return the SNR in 0.1dB increments. A value of 0x014a translates to an SNR of 33.0 dB. > I need to script all of this up, so I can do a more thorough jobe, but > so far every encrypted channel I've looked at is good, every clear > channel bad. Given a pattern like this, I'd say that Comcast is doing > this on purpose, to nudge people into getting set-top boxes. Doubtful. While I don't trust Comcast any further than I can throw them, I suspect in this case you will find that your situation is greatly improved once you update your driver. Devin -- Devin J. Heitmueller - Kernel Labs http://www.kernellabs.com _______________________________________________ ivtv-users mailing list [email protected] http://ivtvdriver.org/mailman/listinfo/ivtv-users
