2009 digital broadcast PC requirements

[broderp]

Sorry if this is in the wrong spot,

has anyone been looking into PC requirements and sage TV for the new standards coming out in 2009?

I'm looking at making a new PC (dedicated for SAGETV) with 3-4 HD tuners. I don't feel my current rig, Intel 2.8Ghz, ATI card, 3 tuners will function very well in this new environment.

Anyone recording multiple HD channels, could you give me an idea of what to spec out.

I'm thinking Intel QUAD CORE, 2.x Ghz or better, 1+Ghz FSB, and appropriate memory.

I'm not sure what tuner cards to use, or how the cable company will be broadcasting the signal (will I require separate boxes for each input or will it be like the current cable system I can splice multiple times)

Raymond

[PAF]

When recording multiple HD streams, the biggest problem is usually the hard drive bandwidth the machine has, especially if using the OS and the recording drive as one.

With the ATSC transmissions (The HD stuff) being, practically, MPEG 2,
(http://en.wikipedia.org/wiki/ATSC_Standards) the only thing the computer is doing is recording the stream (and if watching, reading the stream). Very little computing power is involved in this process but when you think that an HD stream is somewhere around 5GB per hour, recording 4 streams is like recording 20GB per hour... now try reading those for streams at the same time and the computer is doing a 80GB transfer in 1 hour. That is a lot data transfer for a hard drive to handle.

I have 3 HD tuners setup to run and sometimes SageTV uses all 3 at the same time, including 1 or 2 streams being read at the same time. I have 3 SATA I hard drives working in raid 0, which gives me enough bandwidth for those HD tuners. 1 hard drive per tuner is probably overkill but because of overhead transaction or other practical problems in transfer rates, I wouldn't go over 2 HD tuners per hard drive to ensure you can read and write those 2 HD streams.

Processing power wise, anything is good for TV watching... It is important when you try transcoding or watching MPEG 4 AVC or VC1 or other complicated codecs that require processing power. So, if you have multiple clients and plan on watching multiple complicated codecs is when the process gets VERY important. Either way, quad core processors are pretty cheap these days, especially the AMD chips (even though they are slightly less powerful then the Intel chips...)

I run a AMD Phenom Quad Core and I have 2 HD Clients/Extenders and I don't have any problems with watching the more complicated stuff simultaneously... even when doing a background transcoding.

Hope this helps

[Mitch G]

I have a core2 duo (2.2GHz) with 2 standard def tuner cards and a HDHR on the network driving two HD100 extenders. It hardly breaks a sweat. So, a quad should be way more than enough.


Mitch

[stevech]

80GB/hr = 22MB/sec.
My cheap SATA RAID1 will do that and a bit more, but I'll guess that now and then there'd be a stutter/glitch.

[GKusnick]

Originally Posted by broderp

I'm not sure what tuner cards to use, or how the cable company will be broadcasting the signal (will I require separate boxes for each input or will it be like the current cable system I can splice multiple times)

The new digital broadcast standards are for over-the-air broadcast TV, not for cable. Your cable provider may decide to phase out support for cable-ready analog TVs, but they're not required to by law. Are you looking to switch from cable to OTA digital broadcast? Or are you thinking about upgrading your analog cable service to HD digital cable? Or some mix of the two? That will determine what sorts of tuners or capture devices you need to look at.

[pjpjpjpj]

I've got a very cheapo, old, low-end system, and I store all my recordings on USB hard drives (formatted with 64K blocks per Sage recommendation, of course). I have four ATSC tuners (2 HDHRs). I have recorded 3 HD TV shows and watched another simultaneously (all from one single hard drive), and I have never seen any sort of issue with hard drive access at all.

I'm clueless about this stuff and I know all you guys with high-end equipment will give me a thousand reasons why broderp needs this or that, but all I know is that mine works. And not a SATA or a RAID in the house.

broderp - as stated above, if you watch exclusively on an HD Extender (they're in stock right now, get 'em while they're hot!), you don't need any computing power at all. See my specs below.

But as GKusnick said, let us know what you are trying to do, and we can give you better advice.

[stanger89]

Originally Posted by stevech

80GB/hr = 22MB/sec.
My cheap SATA RAID1 will do that and a bit more, but I'll guess that now and then there'd be a stutter/glitch.

Where'd that come from. HD recordings are about 8-9GB/hr (sometimes less), or <20Mbps (2.5MB/sec).

[PAF]

Well, theoretically a SATA II Hard Drive can perform 3GB/s because of the SATA II connection but in reality its not quite that fast.

A typical hard drive usually maxes out at about 60Mb/s because of overhead and other stuff (regardless of connection). In reality it varies from 40 - 80 MB/s. 1 bits = 0.125 bytes, so the hard drive averages out around 480 Mbps and varies from 320 to 640 Mbps.

A good ATSC signal will generate around 20 Mbps of data.
20 X 4 = 80Mbps for writiting and X 4 for reading the four streams and you have 320 Mbps for reading and writing 4 HD streams.

It is right at the 320 minimum mark and probably shouldn't give you any problems even with a hiccup. So, it looks like you can support 4 HD streams of reading and writing on 1 hard drive but I always like to err on the "safe" side and bump the minimum with a raid 0, giving around 640Mbps Min and 1280Mbps Max with an average around 800Mbps.

But remember... if the computer needs to support the OS on the same hard drive, some of the data rate will be given just to keep the computer running and I think that is more than we would like it to be. So, if the recording buffer is on 1 hard drive which is not the OS, you should be OK. If the recording buffer is on the same drive as the OS, you might get hiccups from reading AND writing (a.k.a watching) 4 HD channels SIMULTANEOUSLY. Who watches 4 streams at the same time...

Imagine... 8 HD streams of reading and writing... 640Mbps of data...

I think I did the math right...

[Taddeusz]

I have two single SATA hard drives that work fine for my 3 tuners (an HDHR and an HD-PVR). I can have all three recording while performing ShowAnalyzer scans in real-time on the HDHR recordings and still watch a single HD recording. I only watch TV in one location at a time so it hasn't been a huge deal.

I do have my OS on the same drive as some of the recordings. Here pretty soon I hope to split the OS off as it's own drive. But it has been working fine as-is for a couple years now.

[broderp]

Originally Posted by GKusnick

The new digital broadcast standards are for over-the-air broadcast TV, not for cable. Your cable provider may decide to phase out support for cable-ready analog TVs, but they're not required to by law. Are you looking to switch from cable to OTA digital broadcast? Or are you thinking about upgrading your analog cable service to HD digital cable? Or some mix of the two? That will determine what sorts of tuners or capture devices you need to look at.

I currently have Time warner digital cable, but only use a spliced and amplified coax cable to my tuners. I don't want the hassle and complexity of dealing with multiple tuners, or aiming and moving OTA antenna.

I'm just not sure if the cable system will operate the same way for HD like it does now or if I will need multiple converter boxes for each tuner.

I'm OK with ANOLOG 480i or 480p quality (Like DVD) for my recoreded shows. I suppose if the HD cards have component inputs or HDMI in, I would have to worry about some sort of splitter for HD via component in or HDMI.