Re: use of pulseaudio -- some parameters to call?

Hi Alex,

Can you actually get usable audio in and out when you use “pulse” for
device?
Yes (OpenSuSe) – this is the only way to get some audio operation with
GnuRadio on top of pulseaudio here.
I use Ubuntu 9.10 and 10.04 and none of my computers are able
to work with that setting.
I have Ubuntu 09.04 and 09.10 (some as Linux-Mint, some in a Virtualbox
on top of SuSe) all with pulse audio. All of them have the expected
audio function (in and out).
For the VBox you can set withIn gnuradio als samplerates whcih seems to
be converted in VBox environment. On LinuxMint installation (no VBox,
direct) there are some limits for the samplerate to 44,1, kHz or to 48
kHz.

So, for the operation in GnuRadio, I prefer the use of Alsa “on top” of
Pulseaudio.

But there are still some questions how to get influence to the
parameters?

Even when I looked into the sources I found some methods for changing
parameters, but I did not understand how to call them from GRC
environment supplied with GnuRadio 3.3.1git(20100805)

Using the default alsa devices, i.e.
leaving it empty, works quite all right. According to the pulseaudio
docs, alsa applications will automatically be routed through
pulseaudio via the alsa-plugin.
for my environment on SuSe I had to use the device_name parameter
“pulse” to use the “alsa_plugin” of pulseaudio.
Are you sure your hardware actually supports all those sample rates? I
suspect the reported sample rates are software rates from the mixer
and not native rates of the hardware. I have hardware that only
supports 44.1 and 48 kHz yet I get the same list as you get.

Using other LINUX software e.g. LabView as I understand, it is possible
to change the hardware samplerate of the soundcards.

But for the signal processing in GnuRadio there may no effect if the
hardware samplerate is changed since the software solution in gnuradio
depends on a specfied samplerate inside gnuradio(GRC) – the hardware
samplerate may be tranparently changed in low level routines as the
hardware needs.

Thanks for the answer

M. Hartje


Prof. Dr.-Ing. Michael H.
Labor Hochspannungstechnik / Labor elektrische Messtechnik
Neustadtswall 30; D-28199 Bremen
Tel +49 421 5905-3444 FAX +49 421 5905-3476

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