-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 How do you downsample 50 to 30 Msps? With a fractional resampler? That's highly demanding of your CPU! Do it with the recorded data, not before, if you can afford the memory.
On 04.12.2013 13:47, Paul B. Huter wrote: > Without the low pass filter, I was getting a sequence of D's. The > low pass filter uses a Volk machine, and downsamples the 50M to 30M > with a 5M transition size. I am using the GUI companion on Linux, > but I vaguely recall that I may have had better luck recording when > I just created a Python script on a PC. I will try the script (on > Linux) this afternoon, and I will also try running at 25M > downsampled to 10M. > > In the meantime, any additional comments/suggestions would be > appreciated. > > Thanks. > > Paul B. Huter On Dec 4, 2013 6:29 AM, "Marcus Müller" > <mar...@hostalia.de> wrote: > > With most hardware interfaces, you get notifications when your > driver/interface starts dropping samples -- with UHD you'd see > loads of 'O' indicating overflows. If you don't see that, there is > something really wrong. How does your data acquisition take place? > 50Msps is really a lot for an average PC if you do filtering; I > don't know how your low pass filter looks, but I think it's > probably causing to much computational load for your computer to > process the incoming samples in real time. > > Greetings, Marcus > > On 04.12.2013 12:39, Paul B. Huter wrote: >>>> There must be something with my record, because my 20 seconds >>>> of running only produces about a 180MB file. I am not seeing >>>> any indications of dropped data, though. I am recording to a >>>> RAMDisk, but I get the same results recording to my HDD. >>>> >>>> Does anyone have recommendations for how to ensure I get my >>>> data recorded? I really think that if I cam record the data, >>>> playback will be more what I am looking for. >>>> >>>> Paul B. Huter On Dec 4, 2013 1:20 AM, "Marcus Müller" >>>> <mar...@hostalia.de> wrote: >>>> >>>> Hi Paul! >>>> >>>> I'm gonna go ahead and rearrange parts of your message for >>>> the ease of reply: >>>>>>> My datafile was recorded for about 20 seconds at a >>>>>>> sample rate of 50Msps through a low-pass filter to only >>>>>>> capture 0-30MHz. >>>> 50Msps * 20s = 1Gs (you're sure your file is 8GB in size?) >>>> should be plenty enough, so my guess was totally astray. >>>> >>>>>>> Looking at the configuration for my FFT, and changing >>>>>>> 'Refresh Rate' from the default '15' to '1M' gives me >>>>>>> some extra playback. >>>> what gui toolkit are you using? wx or qt? However, a refresh >>>> rate of one million frames per second... doesn't even >>>> remotely make sense. Since there is no way that your file >>>> source can supply 1024Msps for the GUI sink, even without >>>> throttling, I don't know what the (wx or qt or whatever) FFT >>>> sink does in that case. I'd have to read the source code... >>>> >>>>>>> I like the way the waterfall looks, but I'm having the >>>>>>> same issue as the FFT. >>>> >>>> Ok, this is confusing. The waterfall sink should basically be >>>> able to have one pixel of display per sample going in. And >>>> with 1 billion samples going in, there shouldn't really be >>>> repitions visible, unless your data is repetitive. >>>> >>>>>>> Is there some correlation between data rate on the >>>>>>> record and FFT refresh rate? >>>> No. Refresh rate is just the display refresh rate, i.e. the >>>> speed at which the GUI updates its visualization. >>>> >>>>>>> How is 'FFT Size' used (right now I have that at >>>>>>> '1024')? >>>> Um this is kinda awkward - it's the size of the FFT; how the >>>> samples are internally processed prior to being transformed >>>> depends on the actual FFT sink implementation. >>>> >>>>>>> On a related note - is there a way to get the FFT to >>>>>>> start out in 'Autoscale', or do I need to hit the >>>>>>> button every time? >>>> >>>> No. "Autoscale" is (as far as I know and can remember right >>>> now) not a /mode/ for the qt nor the wx gui fft sink, but >>>> scales the display to fit the data that is display /the >>>> moment the button is clicked/. So, since data can only be >>>> available at run time, you can't do that before running the >>>> flow graph. However, at least for the qt implementation, you >>>> can set y max/y min, if you know it beforehand. >>>> >>>> So: Verify your data is really about 1 billion samples long >>>> and not only a few thousand; if your waterfall looks >>>> periodic, your recorded signal is periodic. >>>> >>>> Greetings, Marcus >>>> >>>> On 03.12.2013 22:45, Paul B. Huter wrote: >>>>>>> >>>>>>> Is there some correlation between data rate on the >>>>>>> record and FFT refresh rate? How is 'FFT Size' used >>>>>>> (right now I have that at '1024')? On a related note - >>>>>>> is there a way to get the FFT to start out in >>>>>>> 'Autoscale', or do I need to hit the button every >>>>>>> time? >>>>>>> >>>>>>> Thanks! >>>>>>> >>>>>>> >>>>>>> On Tue, Dec 3, 2013 at 3:01 PM, Marcus Müller >>>>>>> <mar...@hostalia.de> wrote: >>>>>>> >>>>>>> Most probably your data is simply to short in relation >>>>>>> to the fft length and the amount of samples your >>>>>>> specific graphical FFT amplitude sink drops for >>>>>>> display. Please review you fft length, update rate, and >>>>>>> try out different fft GUIs (qt/wx). >>>>>>> >>>>>>> You could zeropad your data generously to notice the >>>>>>> repitition. However, I think with what you're >>>>>>> describing you might be better off with a waterfall >>>>>>> graph; try them, they're fun :) >>>>>>> >>>>>>> Greetings, Marcus >>>>>>> >>>>>>> On 03.12.2013 21:45, Paul B. Huter wrote: >>>>>>>>>> When I play my data file back through a throttle >>>>>>>>>> and frequency translating FIR filter to an FFT >>>>>>>>>> sink with repeat OFF, it seems to just show a >>>>>>>>>> static plot. However, with repeat ON, I get >>>>>>>>>> playback, but I can't tell when data ends and >>>>>>>>>> starts back over. Is there a way for me to know >>>>>>>>>> when it repeats? Or, is there a way to get >>>>>>>>>> playback with repeat turned off? >>>>>>>>>> >>>>>>>>>> Thanks. >>>>>>>>>> >>>>>>>>>> Paul B. Huter >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> _______________________________________________ >>>>>>>>>> Discuss-gnuradio mailing list >>>>>>>>>> Discuss-gnuradio@gnu.org >>>>>>>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>>>>>>>>> >>>>>>>> >>>>>>>> >>>>>>>>>> > >>>>>>>>>> _______________________________________________ Discuss-gnuradio >>>>>>>> mailing list Discuss-gnuradio@gnu.org >>>>>>>> https://lists.gnu.org/mailman/listinfo/discuss-gnuradio >>>>>>>> >>>>>>> >>>>> >>>> >> > -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.15 (GNU/Linux) Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBAgAGBQJSnyUcAAoJEAFxB7BbsDrLghsH/2M1hLURhotBQpCP8GXVECsG 11X/XYyieteYTdfd8bT/BEdNBWOtefHicimrkXBwXW6oC+50jRbvCwGDQdKrVFCE JltDYvV0YsIM5h4+BqaAE05T1ol1scKKCgJrqKgkorYsjgHMxlSo9XOZF09dRzLT Ib1j52FyH5IZ4RgU7q5hyil5lEGwPEqCyKj4TQFDO8nFLU+l9OboAj3H5Y+G3ew0 BbHyzIe4sZWHmPKGdur+xtJ+84TcNvsVVxgn/kFBRcqQrywk68U5IX2w8Dx+7sMR Dr/hQKXD1yO75YYlO8vXd74hH802tur5/BW/Q0SRGGjcr2sS2vnFr1akcIFq7QA= =Irgo -----END PGP SIGNATURE----- _______________________________________________ Discuss-gnuradio mailing list Discuss-gnuradio@gnu.org https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
