Re: Reliable work-horse capture device?

[David Liontooth <lionteeth@cogweb.net>]

Mauro Carvalho Chehab wrote:
> Hi David,
>
> Em Mon, 14 Sep 2009 19:41:13 -0700
> David Liontooth <lionteeth@cogweb.net> escreveu:
>
>   
>> We're setting up NTSC cable television capture devices in a handfull of 
>> remote locations, using four devices to capture around fifty hours a day 
>> on each location. Capture is scripted and will be ongoing for several 
>> years. We want to minimize the need for human intervention.
>>
>> I'm looking for advice on which capture device to use.  My main 
>> candidates are ivtv (WinTV PVR 500) and USB, but I've not used any of 
>> the supported USB devices.
>>
>> Are there USB devices that are sufficiently reliable to hold up under 
>> continuous capture for years? Are the drivers robust?
>>
>> I need zvbi-ntsc-cc support, so a big thanks to Michael Krufty for just 
>> now adding it to em28xx. Do any other USB device chipsets have raw 
>> closed captioning support?
>>
>> I would also consider using the PCIe device Hauppauge WinTV-HVR-2200, 
>> but I need analog support.
>>
>> Appreciate any advice.
>>     
>
> If you look for stability, the most important item is to choose a good stable
> server distribution, like RHEL5. You'll be better serviced than using a desktop
> distro with some new (not so stable) kernel and tools.
>
> In terms of stability, the PCI devices are generally more reliable, and, among
> all drivers, bttv is the winner, since it is the older driver, so, in thesis,
> more bugs were solved on it. That's the reason why several surveillance systems
> are still today based on bttv. If you need a newer hardware, then you may choose
> saa7134, cx88 or ivtv devices.
>
> I don't recommend using an USB hardware for such hard usage: it will probably
> have a shorter life (since it is not as ventilated as a PCI device on a
> server cabinet), and you might experience troubles after long plays. In terms
> of USB with analog support, em28xx driver is the more stable, and we recently
> fixed some bugs on it, related to memory consumption along the time (it used to
> forget to free memory, resulting on crashes, after several stream
> start/stop's). 
>
> There's a tool at v4l2-apps/test made to stress a video driver, made by
> Douglas. I suggest that you should run it with the board you'll choose to be
> sure that you won't have memory garbage along driver usage.
>
> Cheers,
> Mauro
>   
Thank you, Mauro! I much appreciate the advice.

I also see I misattributed the zvbi-ntsc-cc support for em28xx -- kudos 
goes to Devin Heitmueller for great work on this.

As for the ventilation issue for USB devices, that may not be a serious 
obstacle. If the USB sticks such as Hauppauge HVR-950 have reliable 
components, we could strip the plastic casing and mount the unit next to 
a fan inside the case.

Memory leaks would be a serious problem on the other hand; thank you for 
pointing to the stress test.

I would be happy to use bttv, but I can't find cards. I also need to 
grab audio off the PCI bus, which only some bttv cards support.

We've been using saa7135 cards for several years with relatively few 
incidents, but they occasionally drop audio.
I've been unable to find any pattern in the audio drops, so I haven't 
reported it -- I have no way to reproduce the error, but it happens 
regularly, affecting between 3 and 5% of recordings. Audio will 
sometimes drop in the middle of a recording and then resume, or else 
work fine on the next recording.

Our fallback is ivtv. I was hoping to use USB so that we could get 
blades instead of 3U cases; it's also getting hard to find good 
motherboards with four PCI slots.

Cheers,
Dave