Re: [Discuss-gnuradio] ATSC demod tips

[Eric Blossom]

On Mon, Sep 22, 2008 at 09:05:56AM -0700, Ben Green wrote:
> 
> 
> Wuest Brandon-WTVR47 wrote:
> > 
> >  
> >> I got a few underruns during the "usrp_rx_cfile".  
> >> About 10 in 10 seconds.  The raw data file is 446 meg.
> > 
> > Underruns are bad.  
> > 
> > Try capturing the data to a ram disk instead of your hard drive if you
> > do not have a faster hard drive setup available (i.e. RAID).  I used the
> > ATSC demodulator a few months back and was never able to successfully
> > store that data down to my hard drive, so I allocated a 512 MB ramdisk
> > and used that which worked great.
> > 
> I am having the same issue. When using a ramdisk I get no usrp overruns but
> still the output file is empty. When putting the output of each py file in
> its own file, I found btl-fsd.py outputs nothing. Are there any obvious
> reasons why this would be happening? Is there anything I can do to narrow
> down the problem?

If you are trying to capture continuous data, there is no substitute
for a disk subsystem that can sustain the required throughput.  In
general we've had better luck using ext2 file systems rather than ext3
file systems.  (You can mount an ext3 as an ext2.)  Posting the ext3
journal was causing a problem last time I looked at this in detail
(> 2 years ago).

Eric