Hi,

I increased the size of the output buffer but, I'm still having the problem. With a buffer of 262144 bytes, at 2.048 Ms/s, it should be full every 16ms, but my program indicates 64ms. Could it be due to a limitation on USB ports, or on my Device (Terratec Cinergy TStick RC) ?

Well actually ... now that I rechecked, I think the problem is your math :) 262144 bytes / (2048000 samples/s * 2 bytes / sample ) = 64 ms. Cheers, Sylvain

Thanks for your help. I though IQ samples were encoded on 8 bytes. This explains my error. Cheers Frederic -----Message d'origine----- De : osmocom-sdr-bounces@lists.osmocom.org [mailto:osmocom-sdr-bounces@lists.osmocom.org] De la part de Leif Asbrink Envoyé : lundi 17 décembre 2012 14:53 À : osmocom-sdr@lists.osmocom.org Objet : Re: Information about the sampling rate of the RTLSDR driver Hello Frederic, Each sample is I and Q with 8 bit each. That is 2 bytes. When you sample at 2.048 Ms/s you get 4096 bytes/ms so your observation that it takes 2 ms to fill the buffer is fine:-) The buffer size is not critical. In my project Linrad it is a user parameter because small buffers may be useful for radio amateurs who want a small delay from antenna to loudspeaker when doing two-way communication while larger bufers may be helpful on slower computers. I tried buffers from 2048 bytes to 524288 without errors on a fast computer. You are not doing anything wrong:-) Leif

Hello,

I am testing a DVB-T USB key including the Elonics E4000 chipset and I want to check the sampling rate of this card. I set up the sampling rate at 2.048 Ms/s (rtlsdr_set_sample_rate), and my storing buffer is 8*1024 bytes, so I expect receiving 1024 I/Q samples every 500 microseconds. I am using the rtlsdr_read_async function to read the samples. Unfortunately the loop in my program indicates that 8*1024 bytes are read every 2 milliseconds. I am using the gettimeofday function to measure the time in microseconds. Does this result mean that the best I can do is to read some samples every 2 ms at 2.048 Ms/s. This would mean that I am missing 1.5 ms of signal. Is that correct or I am doing something wrong ?

Thanks for your help. Frederic

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