What kind of hardware required for HDHR Recording computer?

Help and support for HDHomeRun DVR and HDHomeRun software for Windows 10, Mac, Android, XBox, etc.
Ken.F
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Re: What kind of hardware required for HDHR Recording computer?

Post by Ken.F » Fri Aug 02, 2019 8:10 pm

averyfreeman wrote:
Fri Aug 02, 2019 4:15 pm
On a practical level, what happens if I record something that's broadcast in 4K - will I be able to view it even without a video card capable of 4K, on a 1080P televison? Do I need to see if I can find HEVC codecs for FreeBSD?
In my experience (on Linux) you don't need a special video card if your processor can decode it fast enough. My i7-4770 can play them in Kodi with the onboard Intel graphics but it hits the CPU pretty hard. My Pentium G860 can't keep up with it. It tries to play but the video stalls every few seconds.
I had a few 4K recordings here but I deleted them recently. I could have sent you a test clip to try out. The next time I get one I'll let you know. I have a 4K MLB game scheduled to record on 8/3 but I'm not sure if it will record or not. It's listed in the HDHomeRun guide but it doesn't show up in the guide on the FiOS website.

jasonl
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Re: What kind of hardware required for HDHR Recording computer?

Post by jasonl » Sun Aug 04, 2019 4:15 pm

32 channels of DOCSIS 3.0 is only like 1242Mb/s total, and that's shared between however many hundred people are on that same node, so providers usually don't want to overprovision that much. From what I've seen on Charter, the max you can get on 3.0 is 400Mb/s; gigabit requires 3.1.

60fps means it's progressive, 30fps means it's interlaced.

The short answer is that you won't be recording anything at 4K because it's not available from Comcast and likely will never be in a format that the HDHomeRun can receive.

averyfreeman
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Re: What kind of hardware required for HDHR Recording computer?

Post by averyfreeman » Mon Aug 05, 2019 2:30 pm

jasonl wrote:
Sun Aug 04, 2019 4:15 pm
32 channels of DOCSIS 3.0 is only like 1242Mb/s total, and that's shared between however many hundred people are on that same node, so providers usually don't want to overprovision that much. From what I've seen on Charter, the max you can get on 3.0 is 400Mb/s; gigabit requires 3.1.

60fps means it's progressive, 30fps means it's interlaced.

The short answer is that you won't be recording anything at 4K because it's not available from Comcast and likely will never be in a format that the HDHomeRun can receive.
If it's 3.1 how come the downstream channels are QAM256 though? I got the impression from the wikipedia article about DOCSIS that 3.1 is QAM4096: https://en.wikipedia.org/wiki/DOCSIS
DOCSIS 3.1 : First released in October 2013, and updated several times since, the DOCSIS 3.1 suite of specifications support capacities of up to 10 Gbit/s downstream and 1 Gbit/s upstream using 4096 QAM.
So the HDHR Prime can only record MPEG2 streams? Is there like a specification manual for the prime or the API somewhere?

Basically, what you're saying is 4K will be in HEVC and the prime won't stream it? Am I missing something?

Thanks

EddieP
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Re: What kind of hardware required for HDHR Recording computer?

Post by EddieP » Mon Aug 05, 2019 2:50 pm

Most of my Comcast HD Channels are H264 and the Prime has no problem recording them.

signcarver
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Re: What kind of hardware required for HDHR Recording computer?

Post by signcarver » Mon Aug 05, 2019 2:52 pm

No, you are getting it all wrong... It is codec agnostic... doesn't matter if mpeg2, h264, or hevc... it requires ts streams over qam, it is expected that most hevc channels won't be available on linear qam but by ip.

Also at some way distant point when all legacy current cable boxes and d3 modems are gone, there may no longer be any qam (up to 256) and that everything will be ofdm and qam 4096.

jasonl
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Re: What kind of hardware required for HDHR Recording computer?

Post by jasonl » Mon Aug 05, 2019 4:59 pm

DOCSIS 3.1 is capable of going up to 4096QAM. That doesn't mean providers will actually go that high, as denser constellations require higher signal to noise ratios to function properly. To visualize how this works, say you have a 4"x4" piece of paper. Divide it up with lines every inch, giving you an 8x8 grid. This is equivalent to 64QAM. Now, take that same size paper and divide it up with lines every half inch, giving you a 16x16 grid. This is equivalent to QAM256. Then, take that same size paper and divide it up with lines every 1/8th of an inch, giving you a 64x64 grid. That's 4096QAM. Each one of those squares represents a specific value. In 64QAM, it gives you a 6 bit value, since 2^6=64. In 256QAM, 8 bits, since 2^8=256. In 4096QAM, 12 bits, since 2^12=4096. Now imagine that you're throwing a dart at the grid, and which square you hit in there gives you the specific value. 64QAM gives you much more room for error in where you hit to still get the number you intended to hit, while you have to be incredibly precise on 4096QAM because your squares are 1/8"x1/8". The more precise you can be (the cleaner your signal is), the more bits you can represent with each hit. Do it over 5 million times per second, and that's a basic conceptual description of what digital cable modulation looks like. There's obviously a lot more that's going on, but this should be enough to make the point. Cable providers have to balance performance of the system against the requirements for customers to be able to receive the signals, and 256 is a sweet spot.

HDHomeRun PRIME handles HEVC fine. The problem is that Comcast doesn't have 4K channels because they don't have enough bandwidth for traditional 4K channels, and that's unlikely to change. What 4K they do have is delivered as VOD via internet bandwidth rather than TV bandwidth, and that can only be accessed by their devices, not by CableCARD devices.

averyfreeman
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Re: What kind of hardware required for HDHR Recording computer?

Post by averyfreeman » Mon Sep 02, 2019 6:35 am

jasonl wrote:
Mon Aug 05, 2019 4:59 pm
DOCSIS 3.1 is capable of going up to 4096QAM. That doesn't mean providers will actually go that high, as denser constellations require higher signal to noise ratios to function properly. To visualize how this works, say you have a 4"x4" piece of paper. Divide it up with lines every inch, giving you an 8x8 grid. This is equivalent to 64QAM. Now, take that same size paper and divide it up with lines every half inch, giving you a 16x16 grid. This is equivalent to QAM256. Then, take that same size paper and divide it up with lines every 1/8th of an inch, giving you a 64x64 grid. That's 4096QAM. Each one of those squares represents a specific value. In 64QAM, it gives you a 6 bit value, since 2^6=64. In 256QAM, 8 bits, since 2^8=256. In 4096QAM, 12 bits, since 2^12=4096. Now imagine that you're throwing a dart at the grid, and which square you hit in there gives you the specific value. 64QAM gives you much more room for error in where you hit to still get the number you intended to hit, while you have to be incredibly precise on 4096QAM because your squares are 1/8"x1/8". The more precise you can be (the cleaner your signal is), the more bits you can represent with each hit. Do it over 5 million times per second, and that's a basic conceptual description of what digital cable modulation looks like. There's obviously a lot more that's going on, but this should be enough to make the point. Cable providers have to balance performance of the system against the requirements for customers to be able to receive the signals, and 256 is a sweet spot.

HDHomeRun PRIME handles HEVC fine. The problem is that Comcast doesn't have 4K channels because they don't have enough bandwidth for traditional 4K channels, and that's unlikely to change. What 4K they do have is delivered as VOD via internet bandwidth rather than TV bandwidth, and that can only be accessed by their devices, not by CableCARD devices.
Ah-hah, gotcha. So I can expect anything attached to a channel not to be 4K - I'd have to use OnDemand with one of their fancy boxes (which I do not rent). Not having any 4K monitors/TVs and not wanting to have to store ginormous 4K recordings, I'm super happy with that.

Those 1080i 5GB+per hour Late Show recordings are huge enough! :)

foxbat121
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Re: What kind of hardware required for HDHR Recording computer?

Post by foxbat121 » Tue Sep 03, 2019 7:46 am

Most cable channels are still use MPEG2 codec (largely because those cable cos still have large amount of old cable boxes that can only do MPEG2) which is extremely inefficient in today's standards. Some switched to H.264 AVC which is much more space efficient than MPEG2. Verizon's test broadcasting of 4K channel uses HEVC which is even more efficient than H.264. And IIRC, the total bitrate for that broadcasting is just around 30mbps.

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