[mythtv-users] What does ATSC poor signal look like? or is the PC not up to it?

[Andre Newman]

On 16 Apr 2009, at 15:58, Travis Tabbal wrote:

> ATSC got pixelated and loses parts of the video and sound for me when
> I had signal issues. The problem is, poor frontend and backend
> performance will look similiar. The best soultion is to connect the
> tuner to another machine that is better equipped and test it there.

Tried it with his laptop and apart from the more distant stations it  
seems ok, there's not another Linux system there I can mess around  
compiling drivers for the HVR 950 on, all production systems and he's  
gearing for a release so I wouldn't be popular if I broke something!  
That's also why I'm doing most of the tinkering for now.

With an indoor antenna it's never simple to know whether you got it on  
a good day or not!
He's said he'll put up an external antenna but that will have to be in  
a month or so.

>
> Make sure the tuner and antenna are working properly for live TV and
> make sure you are tuning an HD broadcast for the test. That is more
> likely to create the errors you are seeing.

Actually it seems exactly the same on SD as HD, which makes me suspect  
USB subsystem as that's carrying the whole multiplex regardless of  
individual channel bandwidth.
>
> Particularly with older drives, try putting another HD in for
> recordings only. I use XFS and set it to allocate 512M at a time. That

We did that, there's one ext3 65GB drive for system & database and  
another xfs 65GB that's just for recordings.
I didn't know about the the allocation size, I'll check that and try  
512M if it's not at that already.
>
> really helped with backend performance on my system. Even a small disk
> will help isolate the problem. Watch the output of 'top' while
> recording to see if the system is getting overloaded. With ATSC, you

It trundles along at 27% user for mythbackend while recording WGBH-HD,  
that's much harder than I remember my 1GHz P3 dual DVBT system working  
but that's in the uk so it was never recording HD.
>
> shouldn't be getting much load on the backend. All it's really doing
> is moving the data around, no encoding and such. USB is a little CPU
> heavy on some systems, so that could be part of the problem for you.

I'll check for any known problems with the USB card he has, maybe it's  
a bad one for high cpu load.

Thanks for the suggestions

Andre