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Re: ehci_hcd map_single: unable to map unsafe buffer on a standard NSLU2

On Tue, Sep 11, 2007 at 04:53:41AM -0700, Thierry Merle wrote:
> I am using a Terratec Cinergy T2 USB tuner on my 266MHz NSLU2.
> When I am recording a DVB-T stream, it takes around 33% CPU (zapdvb process,
> the tool I use to record) but surprisingly, my NSLU2 is much less responsive
> for other tasks (big latencies for ssh, fetchmail, imap and other things
> that run on my box).
> Nevertheless, the recorded file contains the entire stream (video is fluid).
> Do you think this is a CPU related problem?

Isn't DVB-T mpeg?  That would be a lot less work than a raw captured tv
signal (the driver in question mentioned needing 170MBit per second on
the USB port per tuner, which sounds like an awful lot more data than an
mpeg stream would generate).  That would need much more bandwidth from
the cpu, and if the cpu now has to compress the video it would take
quite a lot of cpu.  Even the disk access to write 170MBit/s starts to
add up, especially since the disk is almost certainly on another USB
port.  I am assuming your tuner has hardware encoding to mpeg or that it
is receiving an existing mpeg stream from some other DVB device.

So yes I could see it being simply a CPU issue.

Len Sorensen

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