Playback of Recordings made with SDR Software

[K5KNT]

I have a few recordings I have made using HDSDR (the OS X port). When I try to play them back in QuickTime, iTunes, or Windows Media Player I don't get any audio.  Is there some sort of post processing that I need to do to listen to these in any of the mentioned players? 

[rdla4]

Generally those I/Q recordings choke "music" players, sound editors etc. You most likely have to play them back with the SDR software that they were recorded with.

[ChrisSmolinski]

I wrote this free app for Mac OS X to play back SDR I/Q recordings: http://www.blackcatsystems.com/software/sdr_iq_recording_playback_program.html

It works with recording files in the RF Space format (used by Spectravue and SdrDx), and maybe Perseus (maybe meaning someone sent me a Perseus I/Q file and I got the app to read it in).

This is the app I use to slog through a night's worth of SDR recordings.

Note that I wrote it to scratch my own itch, it is not supported, but if it works for you, consider it a bonus :-)

[cmradio]

VLC works with my SDR....

Peace!

[Echo_One]

I listen either in WMP or VLC.

[Token]

I listen either in WMP or VLC.

I rather doubt you are using WMP or VLC to playback SDR I/Q data recordings.  He is not talking about audio recordings made when using an SDR (that is no different from any audio recording made with any radio), but rather the recorded I/Q data that SDRs output when recording RF to the HD.  This ability to record the RF to the hard drive is one of the things that set SDRs apart from traditional radios.  Most remote SDRs (such as WebSDR) do not include this capability.


T!

[rdla4]

Correct, That is was I was talking about the I/Q data---while it can be played on some "media players" does not make much sense---Audio can be recorded and played back by any number of media players (WinAmp, Winders Media, Adobe CSS/Audition, VLC and on and on.)

I did find that Adobe Audition will open some I/Q recordings, depending on which SDR software recorded it...but the playback is a mish-mash of stuff that was in the passband when recorded. (In my case, a Studio1 I/Q file will play mish-mash in Adobe Audition, but an SDRdx recording produces an error message.)

Playback the I/Q data with your SDR software, so you can tune into individual signals...something I have a hard time getting Audition or other players to do.

Standard disclaimer: Your mileage may vary, depending on which codecs are available to your operating system.

[Token]

On the subject of SDR recordings, and I/Q vs Audio, K5KNT, you do know you can select in HDSDR what kind of recording to make, yes?  Either a simple audio recording of the demodulated audio (can be played back in almost any audio play application), or an “SDR” or I/Q recording of the sample bandwidth?


On the note of I/Q recordings, not sure how many realize it but these recordings are handled much like standard audio wav files.  This means you can often use your favorite audio editing program (I use Goldwave) to edit the I/Q files.  You cannot look at the data, or play back the signal, but you can trim off excess and edit length.  This means if you have a one hour, 800 MB, I/Q file, but only want to keep three minutes of the file, you can trim off the stuff around the nugget you want to keep, and end up with your 12 MB 3 minute file.

Example:  I have a 60 minute, 50 kHz width, SDR recording of a pirate on 6925 kHz.  The voice ID occurs 27 minutes into the recording, and the voice ID plus 2 minutes either side is all I want to keep for my files.  I open Goldwave, use the File / Open menu, select the SDR file I want.  Once open I sue the edit tool to delete the first 25 minutes and last 31 minutes of the recording.  I select “Save”.  This leaves a 4 minute recording with the voice ID in the middle of that 4 minutes.  This 4 minute file is a lot smaller than the 60 minute file, and easier to keep on the “keepers” hard drive.

Try it first on a copy of the file you want, just to make sure you get the timing down right


T!

[K5KNT]

Thanks for all the replies.

On the subject of SDR recordings, and I/Q vs Audio, K5KNT, you do know you can select in HDSDR what kind of recording to make, yes?  Either a simple audio recording of the demodulated audio (can be played back in almost any audio play application), or an “SDR” or I/Q recording of the sample bandwidth?

I am still playing with HDSDR's recording features. I had it set last night to record just the demodulated audio of a scheduled HM01 broadcast but I forgot to stop the playback of a recording I was listening to (I left it on pause) so the recording never started. Boy do I feel stupid. 

I'm still trying to understand the I/Q data stuff.

[Echo_One]

I listen either in WMP or VLC.

I rather doubt you are using WMP or VLC to playback SDR I/Q data recordings.  He is not talking about audio recordings made when using an SDR (that is no different from any audio recording made with any radio), but rather the recorded I/Q data that SDRs output when recording RF to the HD.  This ability to record the RF to the hard drive is one of the things that set SDRs apart from traditional radios.  Most remote SDRs (such as WebSDR) do not include this capability.


T!

That was not clear in his original posting

[blw]

Chris,

On an iMac 2.0 gHz MySdrPlayback works quite well with a Perseus I/O wav recorded last night of Renegade Radio. The output file was played with Audacity beta 1.3.3. Sounds great.

The only problem encountered is a blue box is sometimes drawn in the upper right quadrant of the waterfall after I selected a segment for playing. Otherwise, it still worked fine. For being free and working so well with Perseus files I'm really happy with it. Thanks a lot for putting the program up for download. Much appreciated here!!!

Barry

[ChrisSmolinski]

Thanks, blw. Yes, I see the extraneous blue box as well. One of those things I need to get around to fixing...

BTW... while I am thinking of it... for SSTV, I make use of the PBT (pass band tuning) value. I set it to 1, for 1 kHz offset. Then set the bandwidth to 1.5 kHz (say 6925 for the lower freq and 6926.5 for the upper). This results in the IF filter essentially being 1000-2500 Hz, which works great for SSTV, it just passes the sync and video and filters out everything else.

I'm trying to figure out C-QUAM demod now. I understand some pirate uses it :-)

[blw]

You're right! I never would have thought about doing that, but I went back and looked at your sideband instructions and that would an excellent way to trim SSTV files down. The only thing I would suggest is some 1 mHz increments shown vertically to make lining up the baseline frequency easier when drawing the box if you were to ever revisit the code again. It's still a great tool as is.

Another time saver is how you can point MySDRPlayer over to the Bootcamp drive and directly into the owner desktop directory.

I'm going to Studio 1 in a few weeks and I assume it saves the Perseus wav since it uses the Perseus ExtIO.dll format.

This old 2.0 gHz dual core 2007 iMac still amazes me running XP, Perseus, and Studio 1 like it does.

Barry

[ChrisSmolinski]

This old 2.0 gHz dual core 2007 iMac still amazes me running XP, Perseus, and Studio 1 like it does.

Macs do age much more gracefully than their Windows counterparts.

[blw]

Chris- there must be a file size limit to what MySDRPlayback will take in. I have a wav that is a little over 2 gb with several SSTVs at the end from the Wolverine Radio show. I'm going to have to break my save files into maybe 15 minute segments if I can't find a way around this. Also, I don't know about getting to those SSTV sections with the wav I have from Saturday night. Any suggestions?