HELP Minimum CPU to record DVB-T ?

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xlinknz

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#22415 27-May-2008 20:30

I want to get setup to use a PVR to record DVB-T & I'm confused as to what is actually needed to record H.264 MPEG4 which is what I understand what DVD-T is in NZ

It seems the minimum cpu varies eg from Avermedia or Hauppauge

1.What is the minimum that people out there have been using eg would a Sempron 3800+ 2.2Ghz be enough or dare I say it a P4 2.4Ghz ?

2. Would the specs required be even higher since Freeview will be using Mpeg4 rather than Mpeg2 for HD DVB-T ?

3. I read people have TV3 HD running at <10% CPU if that is the case why would powerfull CPU be needed ?

4. Should I assume the graphics card makes no difference to the CPU required since I assume recording is done before the content gets to the graphics adapter i.e. there is no relationship to between recording and the graphics adapter ?

Regards

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#133655 27-May-2008 20:40

This hasn't been overly tested

There seem to be 2 issues:
Those that have bad cpus have graphics cards that cant cope

and then there are those that have a good cpu and a decent graphics card that can cope.

Basically if you dont have the correct graphics card it is not going to work very well no matter what cpu you have

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xlinknz

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#133657 27-May-2008 20:47

mentalinc: This hasn't been overly tested

There seem to be 2 issues:
Those that have bad cpus have graphics cards that cant cope

and then there are those that have a good cpu and a decent graphics card that can cope.

Basically if you dont have the correct graphics card it is not going to work very well no matter what cpu you have

Thank you for the reply

I was planning on getting at least a GeForce 8500 or 8600 so the graphics adapter will not be the issue

pjv3

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#133659 27-May-2008 20:53

I have a Hauppauge Nova-T stick. Its a USB2 DVB-T device, and I have found next to no cpu usage while just recording (3800 X2). I'm currently using GB-PVR. In my setup, all that happens is the raw output of the tuner is saved onto the disk. An hour of 720p came to around 3.2GB on the disk.

It seems for just recording, the only real requirements is USB2 and something you can write fast enough to.

For example, I have been planning on making an old 2600+ a back end - I would try less but I dont have any other older machines with USB2.

A PCI tuner might run on something slower. PCI-e only exists on newer computers, so speed isn't really going to be an issue there.

Playing H264 is a different story (live or prerecorded)! That's when you need to involve good codecs and a decent CPU or hardware decoder.

pjv3

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#133661 27-May-2008 20:57

And so you can critique my current setup:

3800 X2
7800GT
Hauppauge Nova-T Stick

Playing 1080i (TV3) H264 using a software codec uses about 60% CPU (over both cores), recording, not much over standard idle (maybe 5%?)

xlinknz

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#133716 28-May-2008 07:57

PJV3

Thank you for your reply

It would seem from your experience the cpu issue is not so much recording dvd-t HD but playing it, therefore as you suggest a low spec back end would be ok as long as it has USB2 etc

The front end is what requires a decent CPU and or graphics adapter that supports H.264 for playing HD content

1. Will/are all the dvd-t HD stations also broadcast in SD as it seems that if you record in SD and playback in SD then less CPU would be required ?

2. If I record in HD can I playback in SD ? [downscale ?]

Dingbatt

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#133754 28-May-2008 10:09

xlinknz: ...............

1. Will/are all the dvd-t HD stations also broadcast in SD as it seems that if you record in SD and playback in SD then less CPU would be required ?

2. If I record in HD can I playback in SD ? [downscale ?]

To my knowledge TV1,2 & 3 are only broadcast in HD on DVB-T. They are in SD (MPEG2) on DVB-S.

HD recordings will still require to be processed (converted) to change them to SD. I am experimenting with PSP Video9 at the moment to convert freeview recordings so I can watch them on my PSP. It is VERY processor intensive and takes a long time. I doubt it is practical to do it 'on the fly' to watch your recordings.

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argo

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#133769 28-May-2008 10:47

Thinking a little laterally, I wonder what CPU you could get away with in a GBPVR Server/Popcornhour configuration?

The Popcorn would be doing all the decoding (I'm assuming the the data is streamed in its "raw" state), so very little processing would fall back onto the Server.

Just a thought

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#133906 28-May-2008 16:50

Exactly, recording is nothing more than saving a data stream to disk, it's more i/o intensive than CPU intensive. A DVB-X device is more like a netowrk device than a a/v device; in fact some DVB-x devices install under the netowrk adaptor section of the windows device manager.

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pjv3

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#133979 28-May-2008 21:31

2. If I record in HD can I playback in SD ? [downscale ?]

Not without some form of transcoding first. In GB-PVR you can schedule an overnight process to convert media types. I'm guessing that means it could do H264 to Mpeg2 (I haven't tried it). That would work for playback on older machines, but of course, it may take a while to convert, and the resulting file will be much bigger!

A while back I thought I saw a realtime H264 to mpeg2 transcoder. At the time I ignored it because I didn't need it. From what I can remember, it acted as a proxy that would convert in real time. I'll have another look for it, as something like that would be useful - I've got an older laptop here that would be perfect for mpeg2 playback, but is too slow for H264. Of course this will require some good processing capability at the proxy!

juliant

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#134026 29-May-2008 04:31

PJV3 - I was interested to see that you can play TV with a 7900GT - I was under the impression that the 8000 series cards were needed esp for TV3. Is it an AGP or PCI-e card - given the cpu I assume it is PCI-e
Still gives me a glimmer of hope that my older P4 3.2 Ghz cpu with AGP 7600 GT might just be up to the task? Also keen to know if the ATI AGP HD2600 could be an option - seems like it is close but still has driver issues. Very frustrating that no 8500GT is available as AGP!
If that fails I will see if it works on my bedroom PC - AMD 4200x2 with 7900GT PCI-e. I can utilise this once Vista supports HD and I can view it on the TV in the lounge via my xbox 360 as I do now with Freeview satellite.

xlinknz

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#134048 29-May-2008 07:52

pjv3:

2. If I record in HD can I playback in SD ? [downscale ?]

Not without some form of transcoding first. In GB-PVR you can schedule an overnight process to convert media types. I'm guessing that means it could do H264 to Mpeg2 (I haven't tried it). That would work for playback on older machines, but of course, it may take a while to convert, and the resulting file will be much bigger!

A while back I thought I saw a realtime H264 to mpeg2 transcoder. At the time I ignored it because I didn't need it. From what I can remember, it acted as a proxy that would convert in real time. I'll have another look for it, as something like that would be useful - I've got an older laptop here that would be perfect for mpeg2 playback, but is too slow for H264. Of course this will require some good processing capability at the proxy!

PJV3 a real time H.264 to MPEG2 transcoder for an older laptop - just what I am after !

Let me knowwhat you find and PM me if you like

xlinknz

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#137749 13-Jun-2008 08:38

Just an update

As a test I acquired a Leadtek XP Analogue card [on TM for $35

] and on my P4 2.4Ghz recording Analogue TV as MPEG2 it uses approx 30% CPU and when recording as MPEG4 it uses 75% CPU

I am now confident recording DVB-T MPEG4 on a relatively low spec PC eg my P4 2.4

toaroa

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#141034 28-Jun-2008 14:07

If I've read this right... most of the innards from my old P IV 3.0, P4C800-e, 1Gb, sata 7200, Audigy 2ZS, FX5600 could be put in a HTPC case (after they've been removed and replaced by a newer system which will be used solely in my office, a long way from the Bravia tellie) and I could even expect to record Freeview HD/DVB-T...? However, the main (only?) obstacle will be the FX5600 which, although theoretically capable of 1920x1080, just isn't up to the HD/H.264 de/compression they use in New Zealand. And, because the mainboard only has an AGP and PCI slots, I couldn't hope to get this system to work with DVB-T even if I replaced the graphics card?

Nety

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#141046 28-Jun-2008 15:30

The main problem you would have is as you say the graphics card. Although in theory there are one or two cards you can still get that are agp and capable of hardware decoding the reality is that people seem to have very little luck with them.

Also I tried running a similar spec system just for DVB-S and found it struggled but then I was running Vista on it which may have been the main problem MCE 2005 I am sure would have been ok but then you get into more issues with hardware decoding as XP does not support it properly.

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toaroa

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#141066 28-Jun-2008 17:42

Cheers for your reply. I suspect you're correct.

I may just mothball the parts and wait on reports about the HD 3850 AGP card. I've seen some reports that the hardware acceleration issues which plagued 2400/2600 equivalents may be resolved in the 3850 (provided you've got a SSE2 processor). Then again, at $350 it would be a risk - so many other things could go wrong with this plan.

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