[mythtv-users] No Programs Listed in "Media Library"

[Michael T. Dean]

On 01/27/2014 04:52 PM, Tom Wheeler wrote:
> On Mon, Jan 27, 2014 at 2:00 PM, Michael T. Dean wrote:
>
>> In that case, and because of the "RemoteGetRecordingList() list size
>> appears to be incorrect." message, I'd guess that there was some
>> corrupt/unhandled data in your channel data that, when channel information
>> was pulled in for display with your recordings, caused a failure.  I'm not
>> sure what exactly could cause that, but I'd (wild) guess it could be
>> something like a null character in a channel name or call sign or something
>> like that.  If so, it would be good to find out exactly what was causing it
>> so that we could write code to prevent such bad data getting into the
>> database.
>>
> I think you've nailed it. I noticed in the list of channels that a local
> broadcaster has several channels whose names ended with an garbled
> character rendered on the screen kind of like "3ABN Teaching T□" (rather
> than "3ABN Teaching TV"). I didn't watch or knowingly record those
> channels, and in fact, I deleted them from the list this time around. But I
> do have a copy of the backend.log I ran with the debug setting:
>
>    http://pastebin.com/JB4nTtK7
>
> And I observe that the log line corresponding to a normal channel looks
> like this:
>
> 2014-01-22 20:54:24.766968 D  MSqlQuery::next(DBManager1) Result: "channum
> = 16_1, callsign = KDTL-DT, chanid = 1161, atsc_major_chan = 16,
> atsc_minor_chan = 1, name = KDTL-DT, icon = , mplexid = 7, visible = 1,
> sourceid = 1, GROUP_CONCAT(DISTINCT cardinput.cardid) = 4,2,3,1,
> GROUP_CONCAT(DISTINCT channelgroup.grpid) = , xmltvid = 77034"
>
> while one for one of the offending channels is missing everything after the
> weird character, like this:
>
> 2014-01-22 20:54:24.767209 D  MSqlQuery::next(DBManager1) Result: "channum
> = 25_3, callsign = 3ABN-DD, chanid = 1253, atsc_major_chan = 25,
> atsc_minor_chan = 3, name = 3ABN Teaching T
>
> And looking at a database backup I made when I was having the problem, I
> can see that the character in the channels table is \0

Wow, lucky guess on my part. Thanks a lot for looking into it and 
confirming. We'll have to get a patch in to scrub the names the channel 
scanner is putting in the database, and potentially any data being sent 
over the protocol.

Who would have thought that broadcasters have started to null-byte 
attack their users. ;) Then again, maybe this is a rebroadcaster/cable 
company--in which case I wouldn't be surprised to find out it actually 
/was/ intended as a null-byte attack against users(-owned equipment).

I may remove the addition to the FAQ entry just because it's unlikely to 
be a common case--and I'm hoping we'll have MythTV patched to handle it 
soon. (Where "we" is likely one of the other devs, who have actually 
been getting work done on MythTV.)

Thanks, again.

Mike