The recorded file was only about 80MB for 10 seconds of recording, and FFT playback was static. Without using the low pass filter, I was seeing a bunch of 'D' (I think) markers, and my playback was choppy.
Nick Foster <bistrom...@gmail.com> wrote: What was the size of the recorded file on the RAM disk? Are you seeing "O" indications (for overflow)? --n On Mon, Dec 2, 2013 at 1:59 PM, Paul B. Huter <paul.b.hu...@gmail.com>wrote: > Nick: > > I tried downsampling the 25MHz to 10, but still was not recording the > whole time I ran (about 10 seconds, with only a couple seconds of > playback). That was when I tried using a RAM disk, albeit at 50 downsampled > to 30. I am using the following for my disk: > > mount -o size=1G -t tmpfs none /mnt/tmpfs > > I then store my data file to /mnt/tmpfs > > Am I doing that wrong? Or is there some other explanation for not storing > data (other than storage size)? > > Again, all feedback and help is appreciated. > > Nick Foster <bistrom...@gmail.com> wrote: > > Paul, > > 30MHz is a big chunk of data to be streaming to anything. A 4GB ramdisk > will be full in 30 seconds at this rate. Do you really not know *a priori* > where > in the whole 0-30MHz spectrum your signal will be? > > I notice now in your first post that you're streaming 25Msps with a > low-pass filter to 10MHz -- if this is the case, why use a 25Msps rate in > the first place? You can make the USRP work for you by asking for 10Msps > (or less, if you know you need less bandwidth) -- it'll handle the > downsampling and filtering. > > --n > > > On Mon, Dec 2, 2013 at 1:32 PM, Paul B. Huter <paul.b.hu...@gmail.com>wrote: > >> I finally got around to trying writing to RAM, and the result is worse - >> my replay FFT is static. >> >> I am trying to record a chunk of spectrum (in this case the shortwave >> chunk, 0-30MHz) and then go back and look at small pieces to find my >> specific data. If someone can provide insight into how to do this, I would >> appreciate it. >> >> Thank you all for all the assistance to date. >> >> Paul B. Huter >> On Nov 25, 2013 9:38 AM, "West, Nathan" <n...@ostatemail.okstate.edu> >> wrote: >> >>> I agree with Nick: that VOLK stuff is all expected behavior. If you're >>> trying to write to a file at high rates you should look in to using a >>> ramdisk/tmpfs. You'll be limited by how much RAM you have rather than >>> IO speed. >>> >>> However, based on your other threads I wonder if you've taken Tom's >>> recent suggestion to just lower your input sampling rate? If you're >>> only interested in ~1MHz bandwidth you shouldn't be sampling at 50 >>> MHz. >>> >>> -nathan >>> >>> On Mon, Nov 25, 2013 at 12:08 AM, Nick Foster <bistrom...@gmail.com> >>> wrote: >>> > Your file sink only records a few seconds of data because your hard >>> drive >>> > can't keep up, not because of any problem with Volk. The Volk machine >>> being >>> > used does not indicate which particular architecture is used for each >>> kernel >>> > -- that isn't printed at runtime. >>> > >>> > --n >>> > >>> > On Nov 24, 2013 9:58 PM, "Paul B. Huter" <paul.b.hu...@gmail.com> >>> wrote: >>> >> >>> >> When running with a USRP source at 25M and a low pass filter down to >>> >> 10MHz, I get something saying "Using Volk machine: sse4_a_64", and my >>> file >>> >> sink only records a couple seconds of data. I ran the volk_profile >>> script, >>> >> but still get the same result. The script returned something other >>> than >>> >> "sse4_a_64" as the best volk to use. My GNU Radio seems to have >>> trouble >>> >> reading configuration files, so is there a way to manually point to >>> the volk >>> >> parameter to use when I load GNU Radio? >>> >> >>> >> Paul B. Huter >>> >> >>> >> >
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