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TVCT on an ATSC-C system

Added by Dennis Graiani almost 6 years ago

Hello:

The cable system I am trying to run TVHeadend on has a mix of Over-the-air and Cable channels on it. All of the channels are modulated 256QAM, but for the local stations, the MPEG TS is passed through unaltered. It's demodulated from 8VSB and remodulated as 256QAM.

This means that these stations have a TVCT instead of a CVCT. This works fine on every TV set on the cable system, but in TVHeadend, there is no channel numbers/names or EPG pulled from the local stations.

Is it possible to have TVHeadend look for the presence of either TVCT or CVCT?

It looks like there is code to do this in src/input/mpegts/dvb_psi.c:2345


Replies (3)

RE: TVCT on an ATSC-C system - Added by Joe User almost 6 years ago

I have not looked at the code, but I would hope that it parses whatever it finds.

I assume you have already enabled the "over the air PSIP ATSC grabber" in Configuration->Channels/EPG->EPG grabber modules. ( Although the setting should only affect EIT and not the parsing of the channel info which should always be done regardless.)

On my system, it properly detects about 2/3 of the "local" channels, but no EIT data at all. (I only briefly tested with a direct connection to a TV, which saw all channel names, but seemed to only show now/next info.)

I do not recall for sure, but I seem to remember not even the cable channels were detected. (Did not care as they are all encrypted and I am only interested in "local" channels.)

I also seem to remember that I tested with using both network options of "ATSC-T" and "ATSC-C" and both had the same results. But that was long ago and maybe the code has changed by now. Have you tried using "ATSC-T"? It does not have a setting for QAM modes, but on my system it still managed to detect properly the QAM/256 modulation. Of course that may highly depend on your hardware and drivers...

I have been meaning to look into this, but never seem to have the time. I manually entered the missing channel info and then setup zap2xml to download EPG information and it has been working fine for a few years now. (hence not being a priority to fix...)

RE: TVCT on an ATSC-C system - Added by Dennis Graiani almost 6 years ago

I made a change to the code, so it will check both CVCT and TVCT on ATSC-C. This seems to have fixed my problem.

I don't think this problem would be unique to me. The cable system transmits the local over-the-air stations with a Blonder Tongue AQT-8 transcoder, which simply passes the OTA 8VSB channels through to QAM.

RE: TVCT on an ATSC-C system - Added by Joe User over 5 years ago

I finally resolved some issues which were preventing me from making new builds for my ATSC system.

Can you post the changes you made so I can try it out? (I do not want to reinvent the wheel...)

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