Tvheadend

Stuart Pearson wrote:

I have recently purchased a second usb tuner for my synology tvheadend setup now that I am in the process of stopping satellite tv forever.

I'm going to assume by that you mean stopping Sky TV, you do know you can use a DVB-S2 tuner on the same dish to receive FTA channels?

The second tuner purchased is identified by tvheadend as a Realtek RTL2832. This usb device is labelled as DVB-T2 for HD reception however various posts I have read indicate linux supports only SD.

No tuner with the Realtek RTL2832 supports DVB-T2 it's DVB-T only however there are a number of devices that do use the RTL2832 along side a Panasonic MN88472/MN88473 which does support DVB-T2.

The Astrometa sticks for example (do you have one of these? I do but don't use it). The Astrometa/Panasonic MN88472/3 does support DVB-T2 on Linux provided you have a newer kernel but it is still a bit flaky the driver only allows one frontend (DVB-T or DVB-T2) to be active at a time which lets be honest isn't very useful.

I am within the Blackhill transmiiter so chose that mux for both usb tuners which returned the same channel list, two of the added muxes failed to find any channels.
Now the interesting part, while investigating the dvblink software to see if an output other than mpeg2 was available (not natively supported by my roku 2) I carried out the same process for scanning the channels, although I selected the full UK list as it was an option available.
I expected both tvheadend and dvblink to match, but this was not case. In addition on both tuners mux frequencies with QAM 256 used for HD transmissions was detected by dvblink. I tried manually adding the muxes detected into tvheadend but no channels were found on the respective frequencies.

Variable signal maybe? I also have a ITE 9135 (two in fact) and two RTL2832 (the Astrometa and a generic one). Both of these tuners are not very sensitive (the ITE less so) and do not cope well with low power signals. It is possible for both sticks to just about pick up extremely low power signals but will struggle to keep a steady lock but hang on long enough to receive some useful data.

If you're using the pre-defined muxes to scan for services in Tvheadend I'm not surprised some muxes are failing as those lists are extremely out of date (not much can be done about those as they're pulled at build time from a github repo managed by someone else). Nor does Tvheadend have a UK wide list of muxes whereas dvblink does.

If you've added a mux manually to Tvheadend it will find the rest of the DVB-T muxes through NIT it won't find DVB-T2 muxes though as they're not provided in the NIT data on DVB-T. I believe it's to stop non T2 devices from attempting to scan those muxes in case they hang or get stuck.

For dvblink,
On the first tuner, identified as ITE 9135 Generic I get the following muxes:

Channel Number          Frequency         QAM         Channels Found
59.                     634000.            64.            44
60.                     634167.            64.            44
61.                     634200.            64.            44
67.                     650000.            64.            10
68.                     650200.            64.            10
69.                     658000.            64.            31
70.                     658167.            16.            31
74.                     674000.           256.            24
76.                     674200.            16.            24
78.                     682000.            16.            31
81.                     682167.            16.            31
82.                     682200.            16.            31

On the second tuner, identified as Realtek RTL2832 I get the following muxes:

Channel Number          Frequency         QAM         Channels Found
12.                     497800.           64.            10
13.                     498000.           256.           10
15.                     498200.           16.            10
24.                     521800.           64.            11
25/28.                  522000.           16.            11
59.                     634000.           64.            44
60.                     634167.           64.            44
61.                     634200.           64.            44
67.                     650000.           64.            10
68.                     650200.           64.            10
69.                     658000.           64.            31
70.                     658167.           16.            31
74.                     674000.           256.           24
76.                     674200.           16.            24
78.                     682000.           16.            31
81.                     682167.           16.            31
82.                     682200.           16.            31

Can anyone provide a logical explanation for the differences in the mux scanning results between tvheadend and dvblink?

I'm not sure what's going on with the dvblink software but I can tell you for sure it's either a driver problem or a software problem as the HD muxes it apparently has picked up neither of the chips ITE/RTL would be able to see anyway and not only that the number of "channels" is way off! :o At present no UK Freeview HD mux has more than 15 services (I'm able to receive two transmitters and both are broadcasting the same number of services on my last count the number of services were 2, 9 and 15).

Now if you do have a Astrometa stick which is able to receive both DVB-T and DVB-T2 you'd see all services as the stick would automatically switch to the Panasonic demod when it detects a DVB-T2 mux (On windows only though) but this does not explain where the software is getting such a high number of services from.

It also looks like you're picking up distant transmitter(s) too or the software is confused as the total number of muxes broadcasting in the UK is 9.

It's not unheard of for some sticks to send garbage data though but I haven't experienced that with any of mine..

Stuart

I hope this helps, it's late and I've already spent 50 mins typing this out (with one hand) so don't be surprised if I've goofed up somewhere.

I'm going to assume by that you mean stopping Sky TV, you do know you can use a DVB-S2 tuner on the same dish to receive FTA channels?

Yes stopping Sky, I only recently discovered S2 usb devices, will consider getting one in future

The second tuner purchased is identified by tvheadend as a Realtek RTL2832. This usb device is labelled as DVB-T2 for HD reception however various posts I have read indicate linux supports only SD.

No tuner with the Realtek RTL2832 supports DVB-T2 it's DVB-T only however there are a number of devices that do use the RTL2832 along side a Panasonic MN88472/MN88473 which does support DVB-T2.

The Astrometa sticks for example (do you have one of these? I do but don't use it). The Astrometa/Panasonic MN88472/3 does support DVB-T2 on Linux provided you have a newer kernel but it is still a bit flaky the driver only allows one frontend (DVB-T or DVB-T2) to be active at a time which lets be honest isn't very useful.

I believe it is the astrometa model, it is this one: http://www.ebay.co.uk/itm/151302022257

I am within the Blackhill transmiiter so chose that mux for both usb tuners which returned the same channel list, two of the added muxes failed to find any channels.
Now the interesting part, while investigating the dvblink software to see if an output other than mpeg2 was available (not natively supported by my roku 2) I carried out the same process for scanning the channels, although I selected the full UK list as it was an option available.
I expected both tvheadend and dvblink to match, but this was not case. In addition on both tuners mux frequencies with QAM 256 used for HD transmissions was detected by dvblink. I tried manually adding the muxes detected into tvheadend but no channels were found on the respective frequencies.

Variable signal maybe? I also have a ITE 9135 (two in fact) and two RTL2832 (the Astrometa and a generic one). Both of these tuners are not very sensitive (the ITE less so) and do not cope well with low power signals. It is possible for both sticks to just about pick up extremely low power signals but will struggle to keep a steady lock but hang on long enough to receive some useful data.

Although I am in the Blackhill area, the Craigkelly coverage also reaches us, and we also have a local relay so that could explain all the channels.

I hope this helps, it's late and I've already spent 50 mins typing this out (with one hand) so don't be surprised if I've goofed up somewhere.

I really appreciate the effort made in providing your comprehensive response, I am going to investigate further, there are certain channels (Channel 5 for one) which are only being listed by the dvblink.

Stuart