[linux-dvb] Is a 733Mhz celeron enough & usb 1.1 sticks
frahm at irsamc.ups-tlse.fr
Sat Oct 14 22:43:11 CEST 2006
> The reason I ask is that i'm interested in setting myself a new
> I'd like to use a modded xbox to run linux and thus use as a PVR. I'm
> aware that linux on the xbox with usb support is no problem. What I'd
> like to know is are there any dvb usb devices apart from the old
> nova/dec from Hauppauge.
> I'd also like know if anyone anyone else has done software mpeg2
> decoding (DVD or standard definition DVB) on linux with a celeron
> 700/733Mhz so I know if that processor is powerful enough.
> All responses welcome.
I have been using a Pentium III, 500 Mhz with 640 MB of Ram to decode
mpeg2 from DVB-T, ADSL-TV (from the Multiposte of my french internet
provider Free who provides TV with the rtsp-protocol) and also for DVD.
The first two cases work very well to look TV on the computer screen,
maybe 30-50 % CPU occupation. With DVD and 16/9 it works also but the
CPU usage is a little bit more limit, there may be very very slight
freezes from time to time. However if you have a DTS-track on the DVD
and you want the computer to decode that plus the mpeg2 video than there
is problem. The DTS-driver (which I used for vlc) is very very
CPU-hungry, even with deactivating the video output I have nearly 100%
of CPU-usage and with video it no longer works. However with standard
AC3 tracks (Dolby Digital 5.1) there is no such problem.
I have also a very old and simple graphics card, 8 MB of Ram and far
below actual standards of performance.
I believe your machine will be very okay provided you have enough memory
(minimum 256 Mb, the more the better). However, I don't know what
happens if you want to decode mpeg2 for a TV-analog Video/SVideo card
(for a TV-connection). I suppose this will work but you should
absolutely use a PCI card and no USB-device for this because with USB
1.1 this will eat up your band width which you may still need for an
On my old computer the USB port is also 1.1 and I have also tested DVB-T
with a USB-Tuner (an AverTV A800 USB 2.0 which compatible USB 1.1). In
principle it works okay but USB 1.1 limits my bandwidth to about 900
KB/s (measured with a USB-hard disk). Normally DVB-T is well below this
value, in my case in France it is about 4-5 Mb/s = 500-600 KB/s (here:
Mb/s = Megabits/s and KB = Kilobytes/s and 1 Mb/s = 128 KB/s). However
in one case, with 16/9 and one particular channel (M6 in France) the
bandwidth was quite close to the maximum and taking into account normal
bandwidth fluctuations in the mpeg-bitrate (this is never constant in
time!) I had in this particular case (modest) freezes due to USB-1.1
Furthermore with USB 2 on a better computer you can access to a full
DVB-T-Multiplex, record several channels in the same time. This usage is
of course impossible with USB 1.1.
Another problem with USB 1.1 is when you want connect a USB-harddisk and
a USB-Tuner because they may share the bandwidth and this may not be
enough to record directly on the USB-harddisk (this depends how many
different USB-controlers you have but on an old PC there is probably
only one even if there are two or more USB-ports).
These are the kind of limitations you may encounter. In general the
processeur seems okay to me but you can have only one full-speed
USB-device (either harddisk or USB-Tuner). If you have a PCI-DVB-T card
the situation changes and you don't have USB 1.1 limitation.
More information about the linux-dvb