> I'm curious, has anyone got the Air2PC to work with cable company video > feeds? I have Charter specifically and while I saw lots of signal the one > time I tried a scan, it never found any channels.
Does your cable feed include any local OTA channels in digital form? If not, I think there is about a 70% chance that the digital channels are encoded using the General Instruments/Motorola "Digicipher II" format, rather than the ATSC or DVB formats that MythTV looks for. The good news is that Digicipher II uses MPEG-2 and is very similar to ATSC. The bad news is that channels will almost certainly be encrypted. In my cable feed, the video and audio streams encrypted for all of the TV channels on the system. The 30 music-only channels, interestingly, are unencrypted, as is the program guide information. I was able to figure this out using the following technique: 1. Scan for channels that had QAM streams on them using mythtv-setup. Since my cable feed uses QAM64, rather than QAM256, I had to patch mythtv/libs/libmythtv/siscan.cpp. 2. Look in the database to get the frequencies at which mythtv-setup found QAM64 streams. Add corresponding lines to .azap/channels.conf: [name]:[freq]:QAM_64:0:0 3. Switch to one of these channels using "azap [name]". 4. Get the list of PIDs on that channel using "dvbscan -c -v -v". A "VIDEO" PID on a U.S. cable system is probably an ATSC video stream. A type 0x81 PID is an AC-3 audio stream. A type 0x80 PID is probably a Digicipher video stream, most likely encrypted. A type 0xc0 PID appears to carry information related to the music channels. 5. To figure out for sure which PIDs are encrypted, the only method I could think of was to patch "dvbtraffic" to look at the "Transport Scrambling Control" bits in each MPEG-TS packet header. These are bits 6 and 7 (most significant bits) in the fourth byte of each header. Both bits are zero for unencrypted PIDs. As I noted above, all of my digital video channels are encrypted. For anyone that cares, this is Stanford University's student housing cable system. Note that Digicipher II uses DES for encryption (or maybe it's Triple DES--I'm not sure). If it is plain old DES, then it should be possible, though not cheap, to crack through brute force. I hope this helps someone... Neil
_______________________________________________ mythtv-users mailing list [email protected] http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
