What is the best internal card I can get to use with MythTV

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What is the best internal card I can get to use with MythTV

Postby oniscidea » Wed Jun 14, 2017 6:51 am

I have a Terratec Cinergy T PCIe Dual card. I've been using it with MythTV for the last 5 years.
At the beginning I had to download & compile drivers to get this card to work because it was not included in the kernel. Years ago the signal meter wasn't working well and I also had other problems like having to configure it manually. Later the Linux driver for that card evolved a little and was included in the kernel.
However all these years I had glitch/noise issues with that card. I don't know if it is the driver or maybe just MythTV application, but the fact is that I have tested several TV's connected to the same aerial and reception was always good, and not-so-good in my HTPC with this card. Audio and image glitches are frequent.
Now I am thinking of renovating my HTPC and getting a new DVB-T dual card. The question is: what would you recommend, based on your experience, having in mind that:
- It must have two DVB-T receivers (dual)
- It must be internal and for PCI express bus
- I will use it with mythbuntu
I'd really like to have a second receiver card to compare performance with my actual Terratec.
So... In your opinion: what is the best internal card I can get to use with MythTV?
Thanks community!!!
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Re: What is the best internal card I can get to use with Myt

Postby oniscidea » Thu Jun 15, 2017 6:51 am

No one uses an internal dual card working out of the box?

I had a look at http://parker1.co.uk/mythtv_novafw.php but don't know if it is actual info.

Good choice seems to be: TBS TBS6280 Dual Tuner DVB-T/DVB-T2 PCI-E: It says "The manufacturer officially supports Linux, although the driver is binary rather than open source. A highly recommended card."
But in https://linuxtv.org/wiki/index.php/TBS6280 I read "driver is NOT included in linux kernel, you must compile a closed (proprietary) or open source driver above to use your TBS6280 card"
Does anyone know if it is actualised info?
There is also a successor of TBS6280 called TBS6281but seems driver still not included in kernel...
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Re: What is the best internal card I can get to use with Myt

Postby MikeB2013 » Thu Jun 15, 2017 8:41 am

I have used a TBS 6280 for some years with no problems.

I have used both the closed and open source drivers and would recommend the open source drivers as they use a much later version of the linux media stack. (V4L).

The open source drivers are at https://github.com/tbsdtv/linux_media/wiki

The downside of both drivers (closed and open) is having to rebuild them every time the linux kernel gets updated, not difficult, but you have to remember to do this.

One other point, if you have both a Terratec and a TBS card installed you will need to make sure the dvb adapter numbering is consistent across reboots (*buntu 16.04 and later uses systemd at startup with many things running in parallel which can cause adapter numbers to change - not good for mythbackend). There are a couple of solutions, one is to use udev rules, the other is to use adapter_nr (this is what i use as I also have a TBS 6981 dual DVB-S/S2 installed)

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Re: What is the best internal card I can get to use with Myt

Postby oniscidea » Thu Jun 15, 2017 9:17 am

Thanks Mike for the info... and for the clue regarding dvb adapter numbering!

So the TBS 6280 is a good option, but I need to compile the kernel on each update... OK!
You say that you are also using a TBS 6981, that I suppose is the successor of TBS 6980. Do you know if TBS 6281 (successor of TBS 6280) and TBS 6285 (successor of TBS 6284) are also good choices?

Apart from that, anyone knows of any dual PCIe card included in the actual kernel?
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Re: What is the best internal card I can get to use with Myt

Postby MikeB2013 » Thu Jun 15, 2017 7:18 pm

oniscidea wrote:Thanks Mike for the info... and for the clue regarding dvb adapter numbering!

So the TBS 6280 is a good option, but I need to compile the kernel on each update... OK!
You say that you are also using a TBS 6981, that I suppose is the successor of TBS 6980. Do you know if TBS 6281 (successor of TBS 6280) and TBS 6285 (successor of TBS 6284) are also good choices?


It is only the drivers you have to re-build (not the kernel) after each kernel update.
As far as I know any of the Dual or Quad TBS DVB-T/T2 PCI-e cards should be fine, as should the cards for DVB-S/S2.

TBS 6205 QUAD FREEVIEW DVB-T2/T/C Terrestrial / Cable Quad TV Tuner PCIe Card is a replacement for TBS 6285

TBS also have muti-standard cards, which I would avoid at this time. There are issues with mythtv/linux drivers which can be overcome but it can be messy. These cards have two frontends per tuner e.g. DVB-T/T2 and DVB-S/S2 but only one demux (so only one of the frontends on each tuner can be used at any one time), which is fine, but you may have to make adjustments to make sure the correct frontend is active. My understanding is that the linux core for DVB cannot automatically handle this situation at present, neither can mythtv.

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Re: What is the best internal card I can get to use with Myt

Postby oniscidea » Fri Jun 16, 2017 6:36 am

Thanks!
Just looking for a card supported by kernel, I also found that the DVBSky T982 card (Dual DVB-T2/T/C PCIe) seems to be a very good option. According to what people says it is supported by standard kernel drivers at least since 2015. Do you have any experience with T982 or other DVBSky cards?
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Re: What is the best internal card I can get to use with Myt

Postby oniscidea » Thu Jul 13, 2017 7:30 am

I decided to give a try to the DVBSky T982 PCIe dual tuner card, so from some weeks ago I am the owner of one of these cards.
I also made a fresh install of mythbuntu 16.04 with mythtv 0.28
The card worked out of the box EXCEPT for the fact that you have to put a firmware file (download it from the web: dvb-demod-si2168-b40-01.fw) in /lib/firmware. Once you put the file there linux does the rest.
The reception is good, but I still have glitches/artifacts that seem caused by bad reception. However my TV receiver does not show these defects, so I have the suspect that:
- Maybe tuner cards have les sensitivity than regular TV receivers (it seems strange to me)
- Or maybe mythtv software has some particularity that produces this phenomenon
I will keep investigating...
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Re: What is the best internal card I can get to use with Myt

Postby fe31nz » Wed Aug 09, 2017 1:01 am

Dual tuner cards need aerials just like single tuner cards. If the card has only one aerial input, but two tuners, the card likely has an internal splitter that takes that one input and passively splits the signal and sends it to each tuner. That means that each of the dual tuners will be getting only just less than half the signal level that you are providing at the aerial connection. If the incoming signal at the aerial connection is only just an OK level, after being split it may not be enough any more. So you are comparing a TV getting a full signal with tuners getting half that signal - not a fair comparision. If you put in another dual splitter between the TV and its aerial, then you can compare them.

As a result of this sort of problem, you may find it is better to use two single tuners rather than a dual tuner. That way, you can use a 3-way spliter with the TV and each tuner getting aroudn 1/3 of the signal level from the aerial, rather than the TV getting half and the dual tuners 1/4. Or you may need to amplify the aerial signal, then split it, and have an extra splitter in the TV connection to prevent it getting too large a signal level.

The other major cause of glitches on playback (where you get the same glitch each time, so it is clearly in the recording file), is when you are recording too many programs simultaneously to the same hard disk. When recording to multiple places on the same disk at once, the heads have to move back and forth all the time, and they are quite slow at doing that (compared to how fast a modern hard disk can write when the heads are on track). So they can take so long to move that mythbackend runs out of RAM buffer space and drops some data. This is a classic disk buffer overrun problem, and causes gaps in the data that is recorded to the recording files. Such gaps are pretty much the same as getting gaps or errored data from a tuner with reception problems - they are not easy to distinguish as they cause the same visible and audible glitches. And unfortunately mythbackend does not specifically log any buffer overrun errors that occur - you only find out about them by the glitches on playback or through roundabout means such as some of the extra logging done if you have "-v record" as an option on your mythbackend command line.

My rule of thumb is to never have more than two scheduled recordings happening on the same disk at the same time, except for overlaps due to pre-roll and post-roll. If I need to do more than that, I add a new hard disk. So now I have seven recording drives.
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