[linux-dvb] usb 2.0 v pci

Patrick Boettcher patrick.boettcher at desy.de
Mon Jun 6 00:45:59 CEST 2005


On Sun, 5 Jun 2005, Felix Domke wrote:
> Wheter the data comes from USB or PCI shouldn't matter that much - both
> are busmastered, so both payloads come in without much CPU-Load.

Agreed. I never worked with _6_ DVB USB device in parallel but with 3. It 
worked without problems.

> However, most PCI cards don't have hardware filtering, so the whole TS
> goes over the PCI-Bus, and must be processed by the CPU. It's not too
> much, however. Even with 6 of them in parallel, it's still only as much
> as one uncompressd PAL signal, which is handled by analog TV cards fine.

The Technisat Sky/Air/CableStar cards have a PID filter.

> USB devices, at least the USB1.1 compatible ones, have hardware filters,
> so you only get the data you need. (Note: at least USB-Nova-T 1.1 cards
> require calculating a checksum over the whole "muxpack", i.e. data, so
> they probably eat a "lot" of CPU time.) If you want to get the whole
> multiplexes, however, you need the full bandwidth anyway (and you
> wouldn't get far with USB1.1 then).

If you want to use DVB-T and USB I would recommend you a device with a 
dib3000p-frontend. It is USB2.0, has a PID filter (32 slots) and this PID 
filter can be disabled (so can deliver complete TS). (Hauppauge Nova-T 
USB2 or Avermedia USB2.0).

Besides the reception qualitiy of these boxes is very good in difficult 
areas, at least this is my subjective impression after testing about 
10 different boxes (which had other frontends).


   Mail: patrick.boettcher at desy.de
   WWW:  http://www.wi-bw.tfh-wildau.de/~pboettch/

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