Maximum of 5 simultaneous recordings per tuner is too low

[Richard Lloyd <rkl@…>]

I have a TBS6984 quad tuner satellite PCIe card, which says that it can record up to 12 HD channels per tuner:

​http://www.tbsdtv.com/products/tbs6984-dvb-s2-quad-tuner-pcie-card.html

Why is it, then, that when running mythtv-setup to configure the backend, the maximum number of simultaneous recordings per tuner is set to only 5?

Note that the BBC/Sky in the UK have launched 24 HD channels on satellite to air Olympics events - with the card I have, this would limit me to only 20 of the 24 :-( Also note that I have an i7 CPU and a very fast Intel SSD (500+ Mbytes/sec write) which are needed for such a large number of simultaneous recordings.

Nearly a year ago, there was a similar complaint on the official mythtv-users mailing list:

http://www.mythtv.org/pipermail/mythtv-users/2011-June/317125.html

As you can see from that mailing list posting, the change is a single hard-coded value in videosource.cpp. Although their suggestion to raise the limit to 20 is arguably too high, my suggestion is that you raise the limit to 12 instead, since I've provided the URL of card that can record exactly that number.

I would also suggest adding something to the setHelpText() call along the lines of:

"Do not set this value above 5 unless you have both a fast CPU and fast SSD for recording."

Although ideally, you want that in a warning dialogue if it's set above 5, but I don't know if you can do that.

[Richard Lloyd <rkl@…>]

Oh, there is a MythTVtalk.com forum thread where it's being discussed, though the only suggestion so far is the same as mine (a source code hack of the 5 value):

​http://www.mythtvtalk.com/maximum-5-simultaneous-recordings-per-tuner-too-low-15617/

[danielk]

There is no inherent limit preventing any DVB card from recording much less than 8191 programs. The limits are imposed by other hardware. The 5 max is to prevent people from setting values like 12 and opening tickets reporting the issues they encounter as bugs. It is easy enough to work around for people who want to live on the edge. I recommend you use a value of 1 or 2 for best results.

[rkl@…]

I must respectfully disagree that it is "easy enough to work around", especially on platforms like Ubuntu, where the Myth TV backend binary packages are in the standard repos and I suspect a large percentage of those users wouldn't have a clue how to download, edit, rebuild and reinstall from source. I only knew it was a source hack because the same issue was on the mailing lists 11 months ago, otherwise I would have had to spend quite a while just finding the line to change.

SSDs are no longer "living on the edge" - with recent HDD price rises and SSD price falls (now 0.50GBP per GB!), more and more users are getting SSDs. As for a tuner that can handle more than the MythTV backend default of 2 channels per tuner per multiplex/transponder, it applies to a lot of the tuners currently on the market, so yet again that is not "living on the edge" either.

As I stated in my feature request, I don't want the default changed from 2, but I do want the maximum raised to 12, with ideally both the help text stating that you shouldn't increase above 5 unless you have a fast CPU/SSD and warning confirmation box before you can accept a value above 5 too (though that last feature might not be possible).

I'm particularly enamoured with your final sentence - "for best results", I should buy 3 quad tuner cards at a cost of 500 GBP to be able to record 24 channels, when one card can do it with 50% capacity to spare. Please re-open this bug, because all of your concerns have been addressed both by my original bug report and this response to your somewhat unsatisfactory reply.

I guess with this intransigence for no good reason, I'm off to rebuild mythtv-setup with a value of 12 as the maximum instead of 5, but to be honest, this sort of brush-off makes me wonder if MythTV just isn't suitable for *any* simultaneous recordings if you claim you should never go above 5 per tuner (which with today's hardware specs is handled easily by a cheap SSD and a middling CPU).

I thought MythTV backend (not the frontend - that's dismal compared to XBMC) might do a better job than the popular tvheadend, but now I learn that the authors have imposed artificially low limits on simultaneous recordings simply because some users might set them too high for their hardware (why not test the CPU and disk speed and set a simul limit based on that? Oh, that's too obvious I guess!) is not the way to get *any* power users of the Myth TV backend to adopt your software. And that may well include me.

[J.Pilk@…]

Recent thread on myth-users:

​http://www.gossamer-threads.com/lists/mythtv/users/515303#515303