Date: Sun, 24 Nov 2019 18:41:47 +0100 From: Polytropon <freebsd@edvax.de> To: FreeBSD Questions <freebsd-questions@freebsd.org> Subject: Audio mixer settings for recording with a microphone Message-ID: <20191124184147.a374384d.freebsd@edvax.de>
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Currently I have the following problem: I'd like to record something to a file using a microphone. I have the following sound hardware in my el-cheapo home PC: % dmesg | grep pcm pcm0: <HDA VIA VT1708_8 PCM #0 Analog> at cad 0 nid 1 on hdac0 pcm1: <HDA VIA VT1708_8 PCM #1 Analog> at cad 0 nid 1 on hdac0 pcm2: <HDA VIA VT1708_8 PCM #2 Digital> at cad 0 nid 1 on hdac0 That is a built-in sound system (located on the mainboard). % cat /dev/sndstat FreeBSD Audio Driver (newpcm: 32bit 2009061500/i386) Installed devices: pcm0: <HDA VIA VT1708_8 PCM #0 Analog> (play/rec) default pcm1: <HDA VIA VT1708_8 PCM #1 Analog> (rec) pcm2: <HDA VIA VT1708_8 PCM #2 Digital> (play) I have one 3.5mm mic input on the rear and one on the front of the system. The rear one doesn't seem to work at all. The front one seems to work, but there is more "background noise" (ca. 1 kHz sawtooth shape + 1 octave higher "beeeeeeeeeeeeep" kind of sound, which I can hear on the headphones). If I do record something (I use audacity), the signal level is very low, and there is more "interference" beep than "used signal". I can control the noise with the last 5% of the levels using the "mic", "igain" and "monitor" control, but the anticipated signal level doesn't really change. My suspicion: I'm doing something wrong with the mixer, but I cannot see what it is... On my old system, I never had such problems - I would simply attach the microphone, increase "mic" as needed, and I could use sox's "rec" command to obtain the audio needed. I put a CMI soundcard (PCI-based) into that system, which FreeBSD did perfectly support. For testing, I set the mixer as follows (important settings marked with an arrow): % mixer -f /dev/mixer0 Mixer vol is currently set to 100:100 Mixer pcm is currently set to 100:100 Mixer line is currently set to 0:0 Mixer mic is currently set to 100:100 <--- Mixer cd is currently set to 0:0 Mixer rec is currently set to 0:0 Mixer igain is currently set to 100:100 <--- Mixer monitor is currently set to 100:100 <--- Recording source: mic <--- % mixer -f /dev/mixer1 Mixer rec is currently set to 100:100 Mixer monitor is currently set to 100:100 Recording source: monitor % mixer -f /dev/mixer2 Mixer vol is currently set to 0:0 Mixer pcm is currently set to 0:0 It does not work, as described above. I tried several microphones. Electret microphones don't work at all. Dynamic microphones do work, but far too low level. I've checked them with a semi-pro mixer system - the mikes work just fine, sufficient level. I chose the one with the "best" signal, RFT DM-2413M. Do "modern" PCs (this one is older than 10 years!) require a pre-amplifier for a microphone? I assume, if I try to connect the mike to the mixer, and the mixer to the line-in of the PC, it won't work as well... but that's the next thing I will try, as I can select "line" as recording inout as well. Never touch a running system. ;-) -- Polytropon Magdeburg, Germany Happy FreeBSD user since 4.0 Andra moi ennepe, Mousa, ...
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