Re: tee-like function via virtual_oss

From: Hans Petter Selasky <>
Date: Sat, 23 Oct 2021 10:01:04 UTC
On 10/23/21 10:57, J P wrote:
> Hi,
> so I finally got some time to play with this thing.
> Virtual_oss does work as you indicate as long as I use sox'splay/rec as in
> your example.
> When I use firefox it does play but when I record there is no sound in the
> recorded file.
> I have firefox compiled as follows:
> Options        :
>          ALSA           : off
>          CANBERRA       : off
>          DBUS           : on
>          DEBUG          : off
>          FFMPEG         : on
>          JACK           : off
>          LIBPROXY       : off
>          LTO            : off
>          OPTIMIZED_CFLAGS: on
>          PROFILE        : on
>          PULSEAUDIO     : on
>          SNDIO          : off
>          TEST           : off
> Firefox uses PA, so I can set the playback device to the newly created
> dsp0.9 (it pops up as a duplicate dps0, I mean, by the same name) but it's
> there, reproduces audio and I can set the volume:
> cat /dev/sndstat
> Installed devices:
> pcm0: <ATI R6xx (HDMI)> (play) default
> pcm1: <ATI R6xx (HDMI)> (play)
> pcm2: <Realtek ALC662 rev3 (Analog)> (play/rec)
> pcm3: <Realtek ALC662 rev3 (Front Analog Headphones)> (play)
> pcm4: <USB audio> (play/rec)
> Installed devices from userspace:
> pcm0: <Virtual OSS> (play/rec)
> dsp0.9: <Virtual OSS> (play/rec)
> Note how the "original" device although it's still there, is not functional
> from firefox (i.e. plays no sound anymore), I do have to switch to the new
> device for playback. This behavior is not shown by mplayer, for example,
> that uses whatever the hw.snd_default_unit is, in this case pcm0, and
> works. Sox's play, needs the env AUDIODEV to be set to the news device to
> work, otherwise plays no sound either.
> Nevertheless, the file recorded when firefox reproduces audio, contains
> only 0s.
> Can you suggest how to solve? Thank you.
> BR


Just a wild guess:

In Firefox there is something called "about:config".

There you enter the key "media.cubeb.backend" to have the value "oss". 
They you restart firefox.