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VIRTUAL_OSS(8) BSD System Manager's Manual VIRTUAL_OSS(8) NAME virtual_oss -- daemon to multiplex and demultiplex an OSS device SYNOPSIS virtual_oss [-h] DESCRIPTION virtual_oss is an audio mixing application that multiplexes and demulti- plexes a single OSS device into multiple customizable OSS compatible de- vices using character devices from userspace. These devices can be used to record played back audio and mix the individual channels in multiple ways. virtual_oss requires the cuse4bsd(3) or cuse(3) kernel module. To load the driver as a module at boot time, place onf of the following lines in loader.conf(5): # FreeBSD < 11 cuse4bsd_load="YES" # FreeBSD >= 11 cuse_load="YES" All channel numbers start at zero. Left channel is zero and right chan- nel is one. The following options are available: -B Run program in background. -S Enable automatic DSP rate resampling. -Q quality Set resampling quality: 0=best, 1=medium and 2=fastest (default). -b bits Set sample-depth in bits for the proceeding commands. -r rate Set default sample-rate for the proceeding commands. -s size Set default buffer size. Size is specified as <samples> or <mil- liseconds>ms. -i priority Set real-time priority. -a amp Set default DSP device amplification as power of two value. -p polarity Set default polarity of DSP device. -e mute Set default mute state of DSP device. -m channels Set default channel mapping of DSP device. -C num Set maximum number of mix channels. -c num Set mix channels for the proceeding commands. -M filter Add a monitoring filter. -t devname Set control device name. -P devname Set playback DSP device only. Specifying /dev/null is magic and means no playback device. -O devname Set playback DSP device only which acts as a master device. This option is used in conjunction with -R /dev/null . -R devname Set recording DSP device only. Specifying /dev/null is magic and means no recording device. -f devname Set both playback and recording DSP device -T devname Install entry in /dev/sndstat. -w name Create a WAV file format compatible companion device by given name. This option should be specified before the -d and -l op- tions. -d name Create an OSS device by given name. -l name Create a loopback OSS device by given name. -L name Create a loopback OSS device which acts as a master device. This option is used in conjunction with -f /dev/null . -F size Set receive filter size in number of samples or <milliseconds>ms for the next device to be created. -G size Set transmit filter size in number of samples or <milliseconds>ms for the next device to be created. -D file Write process ID of virtual_oss to file. -g knee,attack,decay Enable device compressor in receive direction. See description of -x option. -x knee,attack,decay Enable output compressor and set knee, attack and decay. Knee is in the range 0..255, while attack and decay are between 0 and 62. Samples having an absolute value lower than the knee are trans- mitted unchanged. Sample values over the knee are lowered "a little bit". You can think about attack and decay as a measure of how fast or slow the gain of the compressor will work. It is advised that attack is low, so it reacts fast once too high sam- ple values appear. It is also advised that the decay value is higher than the attack value so that the gain reduction is gradu- ally removed. The reasoning behind this is that the compressor should react almost immediately when high volume signals arrive to protect the hardware, but it slowly changes gain when there are no loud signals to avoid distorting the signal. The default values are 85,3,20 . -h Show usage and all available options. EXAMPLES Split a 2-channel OSS compatible sound device into multiple subdevices: virtual_oss \ -S \ -c 2 -r 48000 -b 16 -s 768 -f /dev/dspX \ -a 0 -b 16 -c 2 -m 0,0,1,1 -d vdsp.zyn \ -a 0 -b 16 -c 2 -m 0,0,1,1 -d vdsp.fld \ -a 0 -b 16 -c 2 -m 0,0,1,1 -d dsp \ -a 0 -b 16 -c 2 -m 0,0,1,1 -w vdsp.jack.wav -d vdsp.jack \ -a 0 -b 16 -c 2 -m 0,0,1,1 -w vdsp.rec.wav -l vdsp.rec \ -M i,0,0,0,1,0 \ -M i,0,0,0,1,0 \ -M i,0,0,0,1,0 \ -M i,0,0,0,1,0 \ -t vdsp.ctl Split an 8-channel 24-bit OSS compatible sound device into multiple sub- devices: sysctl dev.pcm.X.rec.vchanformat=s24le:7.1 sysctl dev.pcm.X.rec.vchanrate=48000 sysctl dev.pcm.X.play.vchanformat=s24le:7.1 sysctl dev.pcm.X.play.vchanrate=48000 mixer -f /dev/mixerX -s vol 100 mixer -f /dev/mixerX -s pcm 100 virtual_oss \ -S \ -i 8 \ -x 85,3,20 \ -C 16 -c 8 -r 48000 -b 32 -s 768 -f /dev/dspX \ -a 12 -b 16 -c 2 -m 0,4,1,5 -d dsp \ -a 12 -b 16 -c 2 -m 8,8,9,9 -d vdsp \ -a 13 -b 16 -c 2 -m 10,10,11,11 -d vdsp.fld \ -a 0 -b 32 -c 4 -m 4,2,5,3,6,4,7,5 -d vdsp.jack \ -a -3 -b 32 -c 2 -m 14,14,15,15 -d vdsp.zyn.base \ -a -3 -b 32 -c 2 -m 14,14,15,15 -d vdsp.zyn.synth \ -e 0,1 \ -a 0 -b 32 -c 8 -m 0,8,1,9,2,8,3,9,4,8,5,9,6,8,7,9 -w vdsp.rec.mic.wav -d vdsp.rec.mic \ -a 0 -b 32 -c 2 -m 0,8,1,9 -w vdsp.rec.master.wav -d vdsp.master.mic \ -a 0 -b 32 -c 2 -m 10,10,11,11 -w vdsp.rec.fld.wav -l vdsp.rec.fld \ -a 0 -b 32 -c 2 -m 12,12,13,13 -w vdsp.rec.jack.wav -l vdsp.rec.jack \ -a 0 -b 32 -c 2 -m 14,14,15,15 -w vdsp.rec.zyn.wav -l vdsp.rec.zyn \ -M o,8,0,0,0,0 \ -M o,9,1,0,0,0 \ -M o,10,0,0,0,0 \ -M o,11,1,0,0,0 \ -M o,12,0,0,0,0 \ -M o,13,1,0,0,0 \ -M o,14,0,0,0,0 \ -M o,15,1,0,0,0 \ -M i,14,14,0,1,0 \ -M i,15,15,0,1,0 \ -t vdsp.ctl Connect to a bluetooth audio headset, playback only: virtual_oss \ -C 2 -c 2 -r 48000 -b 16 -s 1024 \ -R /dev/null -P /dev/bluetooth/xx:xx:xx:xx:xx:xx -d dsp Connect to a bluetooth audio headset, playback and recording: virtual_oss \ -C 2 -c 2 -r 48000 -b 16 -s 1024 \ -f /dev/bluetooth/xx:xx:xx:xx:xx:xx -d dsp Create recording device which outputs a WAV-formatted file: virtual_oss \ -C 2 -c 2 -r 48000 -b 16 -s 1024 \ -f /dev/dspX -w dsp.wav -d dsp Create a device named dsp.virtual which mix the samples written by all clients and outputs the result for further processing into dsp.vir- tual_out: virtual_oss \ -S -Q 0 -b 16 -c 2 -r 96000 -s 100ms -i 20 \ -f /dev/null -d dsp.virtual -L dsp.virtual_out NOTES All character devices are created using the 0666 mode which gives every- one in the system access. FILES SEE ALSO virtual_bt_speaker(8), virtual_equalizer(8), cuse(3) and cuse4bsd(3) AUTHORS virtual_oss was written by Hans Petter Selasky hselasky@freebsd.org. FreeBSD August 7, 2020 FreeBSD
NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | NOTES | FILES | SEE ALSO | AUTHORS
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