building hdtv recorder for ota

[stewman]

hello,

I live in Dallas and get most of the primetime HD broadcasts so I'd like to build a hdtv recorder with sage but could use some advice. Here is what i'm currently thinking, use two A180 cards for capture or live viewing, and pipe the picture out of the component HDTV out port on my Nvidia 6600gt video card. Is this possible? I don't have a HDTV tuner for my sony 30" tube yet, and would like to just use the pvr instead.

Here are some questions. Will this work? Can I maximize the SageTV program in the 1920x1080 hdtv output window seen by the computer as a monitor? Will this allow for live viewing? If so, can a program be recorded while another is being viewed live? Also, if I use the A180 card will I need another tuner card to make it work? (the avermedia website says the A180 requires another card to work with XP MCE)

Any advice or thoughts would be appreciated, I havn't built one of these before (although I shoot and edit uncompressed HD for a living).

Thanks!

[oddjob]

If money is no object. Get a dual cpu mothercard, 2 fast cpu's, Nvidea 6600 graphics card and 1 gig of memory.


I currently have a old computer (1.85mhz) with HDTV card and using svideo and can see a small screen version of HDTV. My computer is too slow to record tv, but its all I have until my newegg order arrives.

[sleonard]

I haven't yet purchased or used any of the HDTV cards yet but from what I've read only the Fusion cards allow more than one in a system and they are not (yet) supported by Sage. At least 2 are required for recording one show while watching Live TV.

I don't know about the A180 or needing another tuner card for it.

The 6600GT should be able to do 1080i for your TV.

You should have at least a 3GHz P4 or equivalent for HDTV playback. I don't thing Sage or any Sage related SW can take advantage of dual CPU's (but I could be wrong on that).

[stewman]

hmmmmm. I didn't think hardly any CPU power was required to record hdtv, doesn't it simply copy the ATSC signal exactly as it is received without any recompression?

So is the ATSC decompression done by the CPU alone? I had hoped the nvidia purevideo engine would do most of the work, and that I could make a low power system since it will be on most of the time.

I've downloaded microsofts hd wmv demo files and played them back out full screen 1080i and it looked realy great.

stew

[sleonard]

If the system is just recording the ATSC streams then not much power is needed. It does require quite a bit more to play them back but if you can play WMVHD@1080i you might be OK with the ATSC streams.

[stanger89]

Originally Posted by stewman

hmmmmm. I didn't think hardly any CPU power was required to record hdtv, doesn't it simply copy the ATSC signal exactly as it is received without any recompression?

Correct.

So is the ATSC decompression done by the CPU alone? I had hoped the nvidia purevideo engine would do most of the work, and that I could make a low power system since it will be on most of the time.

Yes, if you have DXVA enabled (Hardware accelleration in the decoder properties) then yes, the video card will do some of the decoding.

I've downloaded microsofts hd wmv demo files and played them back out full screen 1080i and it looked realy great.

If you can play WMV-HD files, you should have no problem play ATSC TS files.

Originally Posted by oddjob

If money is no object. Get a dual cpu mothercard, 2 fast cpu's, Nvidea 6600 graphics card and 1 gig of memory.

No offense, oddjob, but I have no idea what you're talking about. 2 CPUs will do you almost no good as mediaplayback is (currently at least) entirely single-threaded. Purely for video playback, you're better off getting a faster single CPU than 2 slower CPUs or a "slower" dual-core CPU.

The 6600 is a good recommendation, and in general 1GB memory is too, but if you're only running Sage, 512MB is plenty.

[KJake]

Dual CPUs can still help however. The OS can still use both CPUs and if the playback wants to hog all of the first CPU, the OS can continue doing its thing using the second.

[stanger89]

It depends whether and to what degree dual CPUs, or more realistically in this market, dual cores will help. Consider a real-world example or two.

My P4 2.4B can play HD TS files without issue. However HD WMV files, while they play remarkably well with Sage and FSE VMR9 , aren't perfect. What's the solution. Well for argument sake, I could get a second 2.4B and a new motherboard, but that wouldn't really do any good since WMV-HD is basically beyond the capabilities of a 2.4. I would be better off getting a 3.06 (drop in replacement) or maybe a 3.4 or so.

Now compare to say my Athlon 64 3400+, this thing can play anything I can throw at it. Now (ignore for the moment memory and cache issues) it's a 2.4GHz proc, if I were having trouble with say, ffdshow, the logical choice would be to step up to say an Athlon 64 X2 4600. Here the overhead offloaded to the CPU would allow a bit more to be squeazed out of the first, or allow smoother playback.

Of course even that example is a bit contrived because, realistically, I'd most likely get better ffdshow performance from an Athlon FX-55 or FX-57 than from the 4600 due to the higher clock speed.

Hence my argument, for media playback, until software becomes multithread optomized, more clock speed is better (obviously this only applies inside a given architecture).

Of course this is a specific case, of which there are many. This is, say the Client, where playback is the only thing going on. If you were building a server, and especially if you are planning in doing any transcoding, dual-core is definitely the way to go, in that case the 4600 blows away even the FX-57. It's a matter of right tool for the right job. Basically dual-cores, and especially dual-CPUs (due to the specialed motherboards and more expensive CPUs) are not justified for a media playback machine, unless you're building the ultimate ffdshow rig perhaps.

[jblust]

To answer stewman's original question about two A180's, or an A180 and a different tuner:

1. There have been questions as to whether the A180's current drivers would support more than one A180 in the same PC. I haven't seen anyone say that they have this working.

2. The MCE requirement that you need to have another tuner card in addition to the A180 is only an issue with MCE. I have a Sage 3.0 beta setup that only has one A180 in it, and it works fine.

[stewman]

hey guys, thanks for all the tips. I have a 3.2 ghz p4 prescott (socket 478) and have found two motherboards on newegg that have a pci-express slot for my video card i've already got. I was relieved to find the motherboard, it will be the cheapest part in the system. Since the a180 isn't too expensive, i might try one of those. I see that linux's MythTV supports the a180, but I am by no means a linux pro. I'll probably set up the system and install demo software for all the different tv recording programs and see which one works the best.

I've got a quick OT question you might know... I heard somewhere that recording ATSC signals would be banned by law when 2006 starts, and we'd all have to buy our hdtv cards before then if we ever wanted to get one. Is that correct or do you know what i'm referring too?

Thanks!

[stanger89]

Originally Posted by stewman

I heard somewhere that recording ATSC signals would be banned by law when 2006 starts, and we'd all have to buy our hdtv cards before then if we ever wanted to get one. Is that correct or do you know what i'm referring too?

Wrong. Most likely "somewhere" was referring to the Broadcast Flag that was supposed to take effect in June, but the Supreme Court ruled that the FCC lacked the authority to enact it, so it's dormant for now. And it wasn't going to be illegal to record OTA, it was going to be illegal to manufacture "Demodulator products" (recievers basically) that didn't obey the Flag.

[stewman]

Cool, thanks for the right info!