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  Reply # 1113786 22-Aug-2014 22:02
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richms: Are you happy with limiting yourself to 3 of the muxes at once tho?


Since there are only three muxes, yeah, I'm pretty happy with that limitation. :-)

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  Reply # 1113796 22-Aug-2014 22:13
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ahh, there are 4 muxes 602, 538, 570 and 586 for auckland. One seems to only have shopping and other crap at the moment, but that shall change I hope.




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  Reply # 1113887 23-Aug-2014 08:04
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richms: ahh, there are 4 muxes 602, 538, 570 and 586 for auckland. One seems to only have shopping and other crap at the moment, but that shall change I hope.


Ah HAH! Thank you for that, you have explained one of the things that has been puzzling me slightly, namely why a couple of shopping channels weren't showing up.

During setup, one of the guides I was using pointed me to this page, which clearly shows only three frequencies. Furthermore, you'll notice that they show 666MHz as a frequency on the Waiatarua tower, when as you mentioned, it should be 602MHz. I only figured this out because my Panasonic TV shows the frequencies it's using. I didn't think to look at the other channels before I'd removed the aerial.

Rather annoyingly, TVHeadend has "default" data for various countries, and the NZ data matches the list on that page. So 586MHz is not on my current list. 

So back to your question. Yes, I think I can live with only three multiplexes for now, given the number of people in our house, and the lack of quality programming on the fourth. :-) I do, however, have plenty of room to add a fourth if I choose, and the total cost would be $27.20 ($22 for the tuner including shipping, $5.20 for the aerial cable).

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  Reply # 1113899 23-Aug-2014 08:37
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Thanks for showing your setup.
This inspires me to utilize my rpi and dvb-t usb tuners lying around.

Looking forward to your full write up (eg. do you have an aerial antenna for each of the tuner / link to the software you've used, etc).



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  Reply # 1114629 24-Aug-2014 16:06
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The full, and quite long writeup is now available over here.

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  Reply # 1114634 24-Aug-2014 16:22
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Thanks for that. Im going to hit up DX for some tuners shortly. Im wondering how many clients you can get working thru a single pi, as its hardly known for excellent USB and LAN thruput. I have been thinking about getting a banana pi to play with, this might be a good reason to do that.




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  Reply # 1114639 24-Aug-2014 16:36
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richms: Thanks for that. Im going to hit up DX for some tuners shortly. Im wondering how many clients you can get working thru a single pi, as its hardly known for excellent USB and LAN thruput. I have been thinking about getting a banana pi to play with, this might be a good reason to do that.


Well, as mentioned above I got 4 going, 2 HD and 2 SD without issues. That was somewhere around 20Mbps according to TVHeadend. Since it's a 100Mbps network connection, it seems this was likely the Pi processor hitting a limit rather than the network.

I haven't tried recording a few channels while watching others, but that would likely hit limits sooner.

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  Reply # 1114670 24-Aug-2014 17:28
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The problem with the pi is that the ethernet shares the same USB host connection as all the USB ports on the board do, so you are basically going in and out on the same limited bus. I have no idea what the overhead on DVB tuners is ontop of the raw transport stream rate, but I would have thought that just the tuners feeding into the pi would be pretty close to hitting capacity depending on what modes they use.

Does tv headend support splitting it across multiple devices and still showing as a reasonably coherent single channel list to the clients at all? More pi's are cheap enough if it doesnt impede usability.




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  Reply # 1114690 24-Aug-2014 17:39
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richms: The problem with the pi is that the ethernet shares the same USB host connection as all the USB ports on the board do, so you are basically going in and out on the same limited bus. I have no idea what the overhead on DVB tuners is ontop of the raw transport stream rate, but I would have thought that just the tuners feeding into the pi would be pretty close to hitting capacity depending on what modes they use.


Well, it seems to work pretty well, so it seems the capacity is sufficient. 

A single USB2 bus should be capable of 400Mbps. If all 4 USB ports and ethernet share that bandwidth, then 100Mbps for ethernet leaves 300Mbps across the tuners and hard disk. If an HD stream is around 10Mbps, and SD around 2Mbps , then the TVNZ and TV3 muxes will be sending less than 30Mbps total. Sky would probably be less than that. Chuck in some overhead and call it 50Mbps each to be on the safe side and you're only sitting around 150Mbps total for the tuners, leaving 150Mbps for the HDD. More than sufficient.

This does assume we're not sending AND receiving large amounts of data on the ethernet. Since the only inbound data is control information, that's not an unreasonable assumption. The only device with large read and write bandwidth would be the hard disk, and 150Mbps is plenty for both. 

And hopefully that would be the worst case scenario.

Does tv headend support splitting it across multiple devices and still showing as a reasonably coherent single channel list to the clients at all? More pi's are cheap enough if it doesnt impede usability.


Yes - the channel list is a single list of all channels available on all defined multiplexes. If you have multiple tuners with the same multiplexes, you'll only see the single channel list.

Some channels are repeated for some reason, but only because they're showing on different multiplexes. Al Jazeera, for example, appears on three multiplexes, so shows up in the channel list 3 times, but it only works on one of them. It's really trivial to disable services you don't want though.

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  Reply # 1114696 24-Aug-2014 18:04
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Would be interesting to see the breakdown of the acutal bus utilization on a setup like this. Im guessing there is someway to pull this info out of linux with respect to the actual thruput on each of the USB endpoints, but at this stage for me it is all theoretical.

There may be differences between the different tuners as to how much overhead they have as well. That is probably best left as an exercise to someone with more time than me ;)

What I am meaning for the list, is if I have one pi with 2 tuners set up to recieve only TVNZ and one of the kordia muxes, and the other pi set up with mediaworks and the other kordia mux, will an install of xbmc seamlessly show the channels from both as a single list, or will i have to mess about with config on every device that I want to show it on setting up a list myself?




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  Reply # 1114705 24-Aug-2014 18:46
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What I am meaning for the list, is if I have one pi with 2 tuners set up to recieve only TVNZ and one of the kordia muxes, and the other pi set up with mediaworks and the other kordia mux, will an install of xbmc seamlessly show the channels from both as a single list, or will i have to mess about with config on every device that I want to show it on setting up a list myself?

Oh. No, as far as I know you can only point XBMC at one tvheadend server, so I don't think that would work. I could be wrong though.

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