nickolastone / alsa-minivosc-src Goto Github PK

Minimal virtual oscillator (minivosc) soundcard
http://www.alsa-project.org/main/index.php/Minivosc


Fix build error in Linux Kernel v3.8 or later.

---

This is a potential candidate for adding audio support for DroidCam on Linux.
"minivosc.c" creates a virtual mic, which has been modified to to register a generic netlink family for getting data from user sapce.

|--------------------|----------------|--------------|-------------|-------------------------|
| genetlink-client.c # ->| libnl ] -> | snd_droidcam | -->|alsa|-> # arecord or skype or vlc |
|--------------------|----------------|--------------|-------------|-------------------------|

Missing features:
- There is not special syncronization logic yet for passing the data received via netlink to the timer that copies the data up to the recording program.

- genetlink has been modified over the last few kernel updates, so far the code has been tested on Kernel 3.13 (and with libnl3).
It would probably be easy to make it compatible with all 3.x kernels.

Getting started:

First, review the wiki linked at the top.

~$ make          # build driver
~$ make user     # build userspace test program
~$ make insmod   # run insmod to load driver

note: Output from driver will be printed to /var/log/syslog

~$ ./a.out zAudio.s16le.16000.pcm & sleep 1;  arecord -d8 -D hw:1,0 -f u16_le -r 16000 -t raw zzz.pcm

The above will start the userspace test program, which will start sending 100ms chunks of PCM data
via generic netlink to the driver (this is the "agreement" we have between user/kernel space).
We also use arecord to start recording from the mic into zzz.pcm. Again, tail syslog for some debug output.

~$ aplay -f s16_le -r 16000 -t raw  zAudio.s16le.16000.pcm # play original file
~$ aplay -f s16_le -r 16000 -t raw  zzz.pcm                # play recorded file