Devin Heitmueller wrote:
> On Wed, Nov 25, 2009 at 12:52 PM, Dale Pontius <DEPontius@edgehp.net> wrote:
>> I've been using the NTSC side of my HVR-1600s for some time now, and
>> occasionally play with the ATSC/QAM side, hoping to get it into regular
>> usage sooner or later. The other day I first did some ATSC scans using
>> an antenna, and managed to get about what I'd expect for channels, even
>> watched a sampling of them. Then I hooked to an unused port on my
>> splitter/amp and did a QAM scan, wondering what Comcast has left
>> unencrypted. I got a pile of messages :
>> WARNING: filter timeout pid 0x1ffb
>> and dvbscan generated 200+ unlabeled entries.
>>
>> What does the filter timeout message mean?
>> Is there anything I can do about it.
>>
>> I plan to do more looking at this stuff, but was hoping for a little
>> more understanding than just mimicking steps I've googled.
>>
>> Last time I tried this stuff, I came up with only 1 fully identified
>> QAM256 channel - QVC. (Oh Boy!!!)
>>
>> Any suggestions, pointers, etc would be welcome.
>
> Hi Dale,
>
> The ATSC PSIP standard provides things like channel identification
> information and program guide data on MPEG PID 0x1FFB. The channel
> scanner is looking for that data so that it can provide a reasonable
> name for the channel in channels.conf (for example "CBS-HD").
>
> When you see that filter timeout message, it typically means that the
> tuner achieved a signal lock on the target frequency, but the sender
> was not providing any PSIP info. This is really common for QAM, since
> many of the cable companies are not forwarding the channel information
> even for the "must carry channels" (in violation of the FCC
> specification, I might add). It can also mean the channel is
> encrypted (requiring a cablecard), and in that case the cable company
> is not required to provide PSIP info.
>
> Unlabeled entries are cases where a channel was detected but either
> the channel was encrypted or did not have any PSIP info (but
> admittedly all the channel scanners do a lousy job of telling you
> which it was).
>
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:
user@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:
user@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
These are only 2 channels, but everything else is like this - encrypted
channels get a solid lock, clear ones done.
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.
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.
Are there other tools for understanding what I've got here? I've done
a bit more with dvbscan, but once again don't really understand how to
interpret the results. There's a bit more documentation readily
available, but still not a lot on how to interpret the output, beyond
the obvious stuff. I've also seen reference to dvbstream, but don't
seem to have ready access to it under Gentoo, or at least haven't
found what package to install to get it. I've installed and fiddled
a little with w_scan, but have so far been happier with dvbscan.
Thanks,
Dale Pontius
_______________________________________________
ivtv-users mailing list
ivtv-users@ivtvdriver.org
http://ivtvdriver.org/mailman/listinfo/ivtv-users