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Chris -</div>
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Thanks. I'm getting back to a very belated SDR project - the Softrock - from ten years ago. I may need a sound card with capabilities beyond the onboard audio, but initially I want to experiment with Linux-based SDR software. Once I have the software running,
I'll see whether a beefier card, with better ADCs and DACs, is needed.<br>
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<p style="margin-top: 0px; margin-bottom: 0px;">Joel</p>
<p style="margin-top: 0px; margin-bottom: 0px;">973 736 8306<br>
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<div id="divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" style="font-size:11pt" color="#000000"><b>From:</b> pulseaudio-discuss <pulseaudio-discuss-bounces@lists.freedesktop.org> on behalf of Chris Keller <xylo04@gmail.com><br>
<b>Sent:</b> Friday, October 15, 2021 12:07 PM<br>
<b>To:</b> General PulseAudio Discussion <pulseaudio-discuss@lists.freedesktop.org><br>
<b>Subject:</b> Re: [pulseaudio-discuss] Recipe: recording sound card input and output</font>
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<div dir="ltr">Joel,
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<div>In this particular case I'm working on integrating the VARA-FM digital mode into the
<a href="https://getpat.io/">Pat</a> Winlink client. However, I'm excited that this approach will work for other similar use cases. With just a little more work, I can feed pre-recorded audio into decoder/modem programs for automated tests! This was already
possible in some modem programs (e.g. WSJT-X) that had built in such functionality, but doing it through PulseAudio makes the approach repeatable for pretty much any software modem!</div>
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<div>Chris</div>
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<div dir="ltr" class="x_gmail_attr">On Fri, Oct 15, 2021 at 4:20 AM Joel <<a href="mailto:jm-hotmail@hotmail.com">jm-hotmail@hotmail.com</a>> wrote:<br>
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Chris -</div>
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Are you operating an SDR rig or one of the digital modes (e.g., JTx, FTx, etc.)?<br>
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<p style="margin-top:0px; margin-bottom:0px">Joel W2TQ<br>
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<p style="margin-top:0px; margin-bottom:0px">973 736 8306<br>
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<div id="x_gmail-m_8584134862494889316divRplyFwdMsg" dir="ltr"><font face="Calibri, sans-serif" color="#000000" style="font-size:11pt"><b>From:</b> pulseaudio-discuss <<a href="mailto:pulseaudio-discuss-bounces@lists.freedesktop.org" target="_blank">pulseaudio-discuss-bounces@lists.freedesktop.org</a>>
on behalf of Chris Keller <<a href="mailto:xylo04@gmail.com" target="_blank">xylo04@gmail.com</a>><br>
<b>Sent:</b> Thursday, October 14, 2021 9:25 PM<br>
<b>To:</b> <a href="mailto:pulseaudio-discuss@lists.freedesktop.org" target="_blank">
pulseaudio-discuss@lists.freedesktop.org</a> <<a href="mailto:pulseaudio-discuss@lists.freedesktop.org" target="_blank">pulseaudio-discuss@lists.freedesktop.org</a>><br>
<b>Subject:</b> [pulseaudio-discuss] Recipe: recording sound card input and output</font>
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<div dir="ltr">Hi folks,
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<div>I just spent a while figuring out how to solve a particular need and want to save it in the mailing list for posterity.</div>
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<div>I'm an amateur radio operator, and we make extensive use of external sound cards for interfacing computers with radios for digital communication modes. I was experiencing a problem where I really wanted to record received audio (RX) to the left channel
of a file, and transmitted audio (TX) to the right channel. Doing so would let me hear exactly what the modem program heard and sent.</div>
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<div>After much fussing, I found an arrangement that worked: set up a null-sink to represent the rx-tx stream I wanted, then use two loopbacks, one each for RX and TX. Once that was set up, recording the file was simple.</div>
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<div><span style="font-family:monospace"># </span><span style="font-family:monospace">BurrBrown </span><span style="font-family:monospace">chipset used in SignaLink USB</span></div>
<div><font face="monospace">SOUND_CARD="BurrBrown" <br>
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<div><font face="monospace">RADIO_RX=$(pacmd list-sources | egrep "input.*$SOUND_CARD" | grep -oP "<\K[^ >]+")<br>
RADIO_TX=$(pacmd list-sources | egrep "output.*$SOUND_CARD.*monitor" | grep -oP "<\K[^ >]+")<br>
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<div><font face="monospace">pactl load-module module-null-sink sink_name=rxtx sink_properties=device.description=RXTX<br>
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<div><font face="monospace">pactl load-module module-loopback source=$RADIO_RX sink=rxtx channels=1 channel_map=left<br>
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<div><font face="monospace">pactl load-module module-loopback source=$RADIO_TX sink=rxtx channels=1 channel_map=right</font><br>
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<div><img alt="Radio Interface Source_Sink.jpg" width="542" height="128" data-outlook-trace="F:1|T:1" src="cid:17c84ae175818f9c89e1"><br>
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<div>Hopefully this will help someone in the future looking to record both the input and output to a sound card!</div>
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<div>Chris Keller, K0SWE</div>
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