<html><body><div style="color:; background-color:; font-family:arial, helvetica, sans-serif;font-size:13px"><div><span>Still no luck. If I use -R for raw mode a little more data gets through (as seen by file sizes or the Play progress meter) but it seems to be less intelligible if anything. When I write to a file, the size is always in chunks of 16384 bytes (0x4000 or 2^14). At a sample rate of 24000 that's 1/3 second, which is about right compared to what I hear. Without using -R, this doesn't repeat for about a minute. That 16384 must be some buffer size or something in the rtl_fm program, but I haven't found it yet. I think this is supposed to repeat often enough to be continuous. Could computer speed be an issue? I'm on a single core P4 at 3.2 GHz.<br></span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style:
normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;">From rtl_fm -f 146970000 -f 146985000 -f 146910000 -f 146940000 scan2.dat I got this which looks like bursts of noise as rtl_fm is scanning, still all within about 1/3 second:<br><span></span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"><span>http://ab1jx.webs.com/toys/dongle/scan2.dat.gif</span></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;">There's a curious ripple in the baseline which doesn't quite look like power supply ripple, more like something from some filter.</div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: arial,helvetica,sans-serif; background-color:
transparent; font-style: normal;"><br></div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"> Alan</div><div style="color: rgb(0, 0, 0); font-size: 13px; font-family: arial,helvetica,sans-serif; background-color: transparent; font-style: normal;"><br><span></span></div><div>-----<br>Radio Astronomy - the ultimate DX<br></div><div> <br> <div>----- Original Message -----<br> > From: Adam Nielsen <a.nielsen@shikadi.net><br> > To: Alan Corey <alancorey@yahoo.com><br> > Cc: "osmocom-sdr@lists.osmocom.org" <osmocom-sdr@lists.osmocom.org><br> > Sent: Monday, December 31, 2012 1:28 AM<br> > Subject: Re: Trying to use rtl_fm, etc<br> > <br>>> With rtl_fm, I get a tiny burst of audio about once a minute.<br>>> <br>>> A fresh run:<br>>> freebie# rtl_fm -N -f 162550000 - | play -t raw -r 32k -e
signed-integer -b <br>> 16<br>>> -c 1 -V 4 -<br>> <br>> Just FYI, you can see here that:<br>> <br>>> Output at 24000 Hz.<br>> <br>> However you have told 'play' to play the audio at a sampling rate of <br>> 32kHz, even though the audio data is only arriving at 24kHz. So you will get <br>> stuttering as the audio buffer keeps running out and waiting for more data to <br>> arrive.<br>> <br>> For me (under Linux), I get best results using the -r option to rtl_fm to set <br>> the output audio sampling rate to 48kHz, then tell play to play at 48kHz too. <br>> This way my system doesn't have to resample it to 48kHz before it can mix <br>> the stream into the system-wide audio output.<br>> <br>> Note that the -s option sets the signal bandwidth and -r sets the output audio <br>> sampling rate. A lot of people misunderstand the purpose of the -s option, <br>> however you
shouldn't need it unless you are trying to receive data signals. <br>> -W and -N set -s to the correct values for voice transmissions.<br>> <br>> I would also suggest playing a .wav file with the same 'play' options <br>> just to make sure your system can play mono audio at low sampling rates. I know <br>> my sound card drivers won't (possibly because I am using a SPDIF connection <br>> to an external amplifier) so I need the Linux audio system to upmix it to 48kHz <br>> 16-bit stereo or I won't hear anything.<br>> <br>> Cheers,<br>> Adam.<br>> </div> </div> </div></body></html>