Bill, The answer to both of your questions is found in audio.cs in the callbacks.
We record using floats because we floats are what we get from/send to Portaudio. They have the capability to use ints (supposedly), but we were never able to get it to work at 24-bits. Since we already have floats, it is easier to just write the data than to mess with converting them (though it is possible). The reason there is existing code for doing 16 bit integers is because the original wave playback was written for older IQ files which were 16 bit ints. The data is taken at different places depending on whether it is transmit or receive data. We take it from the very front of the chain (before any processing) on RX. We take it from the end (processed audio) for TX. Eric Wachsmann FlexRadio Systems > -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > radio.biz] On Behalf Of Bill Tracey > Sent: Monday, September 12, 2005 10:27 AM > To: FlexRadio@flex-radio.biz > Subject: [Flexradio] Recorded Wave file format > > Anyone know the design rationale for recording IQ wave files as > floats? It looks like the code will playback wave files that are 16 bit > ints. I'd think we could code them as 24 bit ints without (significant?) > loss as that's what the soundcards are feeding us. > > Reason for the question is I'm looking at using FLAC (Free Lossless Audio > Compression - http://flac.sourceforge.net/ ) to compress recorded wave > files and unfortunately it does not handle wave files encoded as > floats. It does apparently handle 24 and 16 bit ints. It looks like > at > one point PowerSDR recorded wave files as ints as there's at least one 16 > bit int encoded IQ wave file (the Aurora file from the Dayton Demo CD) > running around in the wild that PowerSDR will playback. > > Also, a second question, where in the signal processing pipe is the data > being recorded grabbed from -- is it after IQ fixup? That might explain > the recording as floats. Will take a look @ the code and see if I can > puzzle it out, but would be interested to hear from anyone that knows off > the top of their head. > > Cheers, > > Bill (kd5tfd) > > > > _______________________________________________ > FlexRadio mailing list > FlexRadio@flex-radio.biz > http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz
