How does Live HDTV work regarding HDD?

[ChrisBassOMatic]

I have a question really for snapstream?

When watching HD "live", does it go directly from the capture card to the vid card, or does it go to the HDD, then read back from the HDD to the vidcard?

I'm asking because I can record HD, and then watch it later after it's done recording.

But I cannot:
1. watch HD at the same time I'm recording it
2. watch HD live.

My system is apparently too slow. I'm trying to figure out how to upgrade it, and that answer will help me make decisions.

For instance if it's the HDDs slowing me down, I will build a raid array. if not, then I will maybe swap out my HDTV Wonder for a FusionHD5 (God I wish they'd make the right drivers for the MyHD!!)).

My CPU is at 30% when recording HD on the HDTV Wonder.

Current system:
P-IV 2.8 Ghz Northwood w/1Gig ram
2x Hauppage 250
ATI 9600XT
ATI HDTV Wonder
video HDD: 250 mb Hitachi Deskstar PATA dedicated to BTV

[dlandrum]

It saves it to the harddrive. Proof of this is when you pause Live TV.

I have a defect logged for Link where video is jerky when attempting to watch TV at the same time as when I record it. Yet, I am able to watch Live TV.

[ChrisBassOMatic]

Oh yeah that's what I meant, I can "watch" HD live, but only with horrible stuttering.

So if watching it "live" really means going to the HDDs and back, then I'm thinking maybe my HDD is the bottleneck of my system.

[dlandrum]

I seriously doubt it is your drive. Your worst drive may be ATA 100 ... 100MB/s = 360GB/hr ... 44x faster than what you need to record an HD stream (8.25GB/hr).

Yet, I really do not know how the buffer size on a harddrive comes into play.

[Rich A]

If you only have one HD tuner then you can't watch live HD on one channel and do HD recording at the same time. You need two tuners for that. (one tuner can't tune two frequencies at the same time)

If you just want to start watching what is currently being recorded then that would work.

[dlandrum]

If you just want to start watching what is currently being recorded then that would work.

That is the problem ... it does not work ... on the HD recordings ... via Link ... for me; defect logged.

[Rich A]

That is the problem ... it does not work ... on the HD recordings ... via Link ... for me; defect logged.

That's strange. What happens when you try to watch the recording? You do know you can not just watch a channel being recorded by selecting it from the EPG, right?

Say you've got a show being recorded (high def one). Sometime after the recording has started you want to watch it from the beginning. You have to go to the RECORDED SHOWS menu and there you will see it (with a red ball next to it denoting it's currently being recorded) You then select that show just like you would for any viewing of a recorded show. At that point you will be watching the current recording "time shifted" .. in other words you'll be watching it from the beginning while the recording is still going real time.

I know this works fine as because of a unique quirk in my system I cannot view LIVE HDTV. It stutters badly. However if I start an HD recording and wait a minute, then choose to view that recorded show (while it's recording) my stuttering goes away. So for the last few months I've been watching live HDTV using that technique. FWIW, just pausing the live view for a minute and then resuming it also results in perfect playback.

So I've been doing what you are trying to do for a few months now without a problem. Are you selecting the currently recording show from the "Recorded Shows" menu ?? BTW, this was involving the Server. My link PC plays back live HDTV without a problem.

Having said all that, I would also note that the Link machine will need a configuration like that of the server to playback HD. You'll need a DX-9 capable Video card, the latest DX-9, Windows XP with SP2 and the other things. During "pre beta" testing I tested BTV-LINK on 5 different computers. It installed fine on 4 of them. One came right out and refused to install because of the PC's limited video capabilities. One installed fine, and would playback everything like the Server EXECPT Live HDTV. The other three worked fine everywhere. The problems in both non-working cases were various and all due to not having the right hardware or upgrades etc.

[ChrisBassOMatic]

If you just want to start watching what is currently being recorded then that would work.

that is exactly what I'm trying to do, and it does NOT work. If I try to watch the show I'm recording (or ANY pre-recorded show even SD, or any live SD signal) then I get stuttering again. Not only that, but the recording of HD get screwed up, because when I go back later to play the recorded HD show, during those times I was doing something else on the system it's all screwed up but looks good at other times during the recording.

I'm trying to figure out what the bottleneck in my system is. whether it's the HDDs, or I need a better CPU or vidcard.

[Rich A]

that is exactly what I'm trying to do, and it does NOT work.

I'm trying to figure out what the bottleneck in my system is

What exactly happens when you try to watch it?

My Link PC is on a plain old 10/100 LAN. I often have it playing in a window while I'm doing something else on the Link PC.

Halfway down this post you first mention "LINK". So I'm assuming you are having this problem with the LINK PC? Or the Server? Or both?

Note in my tag line that my configuration is very similar to yours. I have over the last few months in Pre-beta testing really tried to over-tax the system. Ran both PVR-x50s capturing AND the HDTV Wonder capturing AND played back a pre-recorded HD show .. all at the same time. I do have a raid 0 for my storage, but I have also done this with one plain old PATA 7200 drive. (my raid is only to increase storage space) I would say your system is plenty big enough to handle it. Did you turn off virus checking for the show storage drive?

[ChrisBassOMatic]

I seriously doubt it is your drive. Your worst drive may be ATA 100 ... 100MB/s = 360GB/hr ... 44x faster than what you need to record an HD stream (8.25GB/hr).

Yet, I really do not know how the buffer size on a harddrive comes into play.

Isn't that "burst" rate? I do not know much about harddrives anymore.

I can record to the hard drive, and play from it, just fine, as long as I don't try to do both at the same time.

While I could live with that temporarily, that's not acceptable long term. It's like having a vcr.

[ChrisBassOMatic]

What exactly happens when you try to watch it?

My Link PC is on a plain old 10/100 LAN. I often have it playing in a window while I'm doing something else on the Link PC.

I edited my post to explain more while you were posting :-)

I am not using Link like the other guy, I just have one box.

[Rich A]

Okay thanks for the clarification Chris. Sometimes when others jump into a thread with the same or similar problem, thing can become confusing for guys who are trying to help. My fault for not paying attention to which guy made which statement. :rolleyes:

From reading your system specs I see no reason it shouldn't work. So there must be something going on in the system that is causing this.

I believe the way the HD works is that the tuned station has it's decoded Transport Stream written directly to the hard drive at all times. In the case of the HD stream this can be as high as 19 mbit/s Notice I said megabits .. not megabytes. Just about any of today's hard drives should be able to handle that easily.

Just one more question. If you record a show completely and then play it back after it's finished, does it stutter ??

[ChrisBassOMatic]

Just one more question. If you record a show completely and then play it back after it's finished, does it stutter ??

Nope then it's fine. As long as I am only reading or only writing, but not both, it works pretty well. It's a Hitachi Desktar PATA 7200 rpm I got only last year.


Man I was hoping someone would say "obviously you need to upgrade x" not "my system is the same and works" which is what people have been telling me :smile:

[Rich A]

Nope then it's fine. As long as I am only reading or only writing, but not both, it works pretty well. It's a Hitachi Desktar PATA 7200 rpm I got only last year.


Man I was hoping someone would say "obviously you need to upgrade x" not "my system is the same and works" which is what people have been telling me :smile:

I feel your pain. But on the bright side, it's most likely you won't have to spend any more money for hardware ...

If the HD programs record fine and you could play them back fine, then that kinda eliminates any problems with the Over-The-Air signal or the recording.

If you can watch Live HD (while nothing else is going on) and THAT is okay, that eliminates a whole bunch of other things.

If doing two things at once (like recording a new show and watching a pre-recorded show) doesn't work then it sure does sound like an I/O thru put problem. But tests have shown that you really don't need a lot of fancy hard drive to do multiple tasks like recording and viewing.

I also have an ATI HD TV Wonder. (works great except for a pesky "live only" TV problem) I know my particular problem is system specific to my server. I can watch live HDTV without a problem on one of my BTV-Link machines.

Things I have found causing thru put problems where video/audio playback is concerned.

Hard drive DMA not enabled.
Hard drive sharing the same controller as a slower drive (CD ROM Drive etc.)
Antivirus Program not turned off for BTV storage drives/folders.
Drive indexing turned on for BTV storage drives.
System Restore not turned off.
Not turning off Windows Swap file for BTV storage drive.

I believe you said you had a separate dedicated hard drive for the BTV storage? If so, and you had maybe a CD or DVD ROM, I would make sure the op. system and BTV program was on the boot drive on the primary controller. Then on the 2nd channel of the primary controller I'd put the CD/DVD ROM. Then on the secondary controller, I'd put the BTV storage drive ... all by itself. If I think of anything else, I'll drop by here.

[ChrisBassOMatic]

Thanks for those ideas I will look into them.
I know the DMA is enabled since I ran the ATI check program (when I was vainly trying to get any of ATIs software to work)

But the rest, is probably all true, so I will dive back in tonight

thanks

[ChrisBassOMatic]

Well defragging seemed to help a lot. I also moved it to its own controller. the other stuff I realized I had already done.

I only used the wimpy XP defrag I ran it through twice, which was still pretty fragged but I was able to record one show and watch a previously recorded show at the same time with minimal stutter. (except skipping forward and back was pretty painful)

I just downloaded perfectdisk and am running it now, so once that's done I might be good to go.

thanks