Tvheadend

Hi people, I will like to discuss about an old issue with tvheadend and annex b networks. Actually I can tune dvb_c annex b with a tbs5881 via usb to a computer, with TBS drivers my dvb_c network was discovered as DVBC using the old parameter "annex b" that was available in old versions of TVH (it used to have annex a, annex b and annex c). Then the "annex combobox" was edited, leaving just DVBC and DVBC annex c, when this modification was made, using crazycat's driver TVH discovered my network as ATSC-C (it is a dvbc network), this was a problem because it causes slower zapping and it didn't load channel names, otherwise using scan-s2 it scanned all fine.

At this moment I placed this issue: http://tvheadend.org/issues/3907#change-19287 then crazycat modified his driver to solve my problem, here is a piece of our conversation at this moment:

"So DVB-C annex B scanned as ATSC PSI table - https://github.com/tvheadend/tvheadend/blob/master/src/input/mpegts/dvb_psi.c#L2674

And i decide make workaround in si2168 demod driver - force annex B if SR < 6000Ks
https://github.com/crazycat69/linux_media/commit/9c548b42b4fd335e4e9d010ccab5832d4e9954b2

So you can setup TVH as DVB-C annex A/C, but driver lock in annex B mode."

Looking at the code, I see that he hardcoded the frontend to make a temporal patch for this specific issue, but it justs solves the problem with tbs5881 and dvbc annex b, while the whole background problem with TVH is still present.

Now the same issue is present with KI STBs which uses AVL demods, they detect my network as ATSC-C and the same problem with zapping and channel names is present (as it was with tbs5881)

I asked libreelec community for help (https://forum.libreelec.tv/thread/9319-8-1-3-libreelec-8-2-for-s905-s905x/?postID=58511#post58511) and I get this answer from afl1:

"Tvheadend is different project, for principal issues you have to complain on tvheadend forum. But I had the same question on tvheadend forum and Jaroslav Kysela explain me: ATSC-C means DVB-C Annex B. BTW there is no standard ATSC-C, this is only introduced by tvheadend."

Source code for AVL driver is here: https://github.com/crazycat69/linux_media/commit/6275d078d972591b9e449c7bad0fa24ea7519380#diff-57be8964a5eb91a0bdc6b391f0a37aeb

I could just modify this section:

if (c->delivery_system == SYS_DVBC_ANNEX_A && c->symbol_rate < 6000000 ) {
+ c->delivery_system = SYS_DVBC_ANNEX_B;
+ c->bandwidth_hz = 6000000;
+ }

and force it to deliver 0x10 just as crazycat did with TBS5881 as workaround, but the problem with TVH will be still present and repeating at any different device with dvbc annex b networks.

I am not an expert of this topic, but I guess that when TVH discovers my network as ATSC-C it uses ATSC tables which are different from DVBC ones. Besides that my network modulate as ATSC-C, it uses DVBC tables.

Is it possible to solve this general problem adding back the "annex b" option in the DVBC scan process?

If you need any ts recording from KI STB (which fails) or with TBS5881 (which works) just tell me.

Thanks very much in advance