[mythtv-users] HD-PVR extremely unstable on backend, works fine on laptop

Raymond Wagner raymond at wagnerrp.com
Sun Sep 25 15:02:12 UTC 2011

On 9/25/2011 10:08, Derek & Cindi Cass wrote:
> When you try the hdpvr on the backend, run lsusb to see which bus it 
> is on.  You need to have it on a usb 2.0 bus, and it is recommended 
> that the hdpvr not share that bus with anything.  I would get the same 
> behavior as you describe when the hdpvr is sharing a bus with anything 
> else (supposedly even another hdpvr, although I only have 1 and can't 
> verify that).
> As you can see, the snobby hdpvr doesn't have to share like the rest 
> of the world is doing.

The HDPVR, digital tuner cards, and any other form of streaming capture 
is only going to have very limited buffer space available.  That data 
must be retrieved from the device within a few hundred milliseconds, or 
else it will be lost.  The HDPVR is not special in this regard.  USB may 
claim to operate at 480Mbps, but it is still the same garbage interface 
designed to be used for low speed peripherals like keyboards and mice.  
It simply cannot handle high throughput and bus contention gracefully.

If you wanted a device that was capable of doing this while sharing the 
bus with other devices, you should have complained for the firewire 
model.  There is very good reason why the professional audio/video crowd 
stuck with it even after the rest of the industry abandoned it for the 
cheaper, supposedly faster, USB.
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