[linux-dvb] Re: dec2000-t success

[Felix Domke <tmbinc@elitedvb.net>]

Franck Arnaud wrote:

> Also how successful is USB at achieving nominal rates in practice, 
> especially when there are multiple devices?
I don't know about multiple devices, but even if isochronous transfers 
have many disadvantages (they consume the given percentage of bandwith, 
regardless if it's used or not - stuffing is used when the datarate is 
lower), one clear advantage is that you REALLY have nearly that 80% of 
11Mbit available. My experiements with the ttusb-nova showed that a 
single, normal, SDTV DVB channel uses about 50% of the bandwith 
available to the device (was set to 80%). Streaming VIVA (highest 
bitrate on astra i know of) into wingrab worked MUCH MUCH better than, 
for example, on the dbox2 (using network). I only got one glitch in a 
whole evening, and that maybe was the fault of Wingrab, or maybe a bug 
in the driver, or maybe a bird flying in front of the dish :)

I really did expect more overhead, and honestly never trusted in USB 
that much.
(but i did only a small estimation based on the number of stuffing 
packets coming in, no reallife values)


felix



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