Use of pulseaudio -- some parameters to call?

GNU Radio
1

Opensuse 11.3 uses pulseaudio as a standard audio-io. Gnuradio 3.3.x
offers alsa audiosink and audiosource.

When I put “pulse” as parameter for the “device_name” in GRC, with
“verbose” in the “~/.gnuradio/config.conf” I got information about
samplerate and other parameters (see below) – in my case: the format
S32LE is selected. – How can I change to use S16LE?

How can I change these audio parameters in GRC? What other parameters
can be changed in ~/.gnuradio/config.conf or by call?
I like to reduce the audio samplerate down to 1000 Hz or up to 192 kHz
– is there any limit to do this when the hardware supports it?

Are there any changes to do in the pulseaudio “default.pa” or by pactl /
pacmd?

Where can I find some more infomation on that? – doxygen does not show
enough information even the audio_alsa_sink.h which is given in the
doxygen object.

Thanks for reading and thinking on answers

Michael

By the way – I made a newer rpm SPEC-file for gnuradio 3.3.0 and
3.3.1-git – anybody interested obtaining this?

my config.conf is:
----------8<-------------

[audio_alsa]

default_input_device = pulse
default_output_device = pulse
verbose = true
----------8<--------------
the verbose output in terminal window of grc is
----------8<--------------

PCM name: pulse
Access types:
MMAP_INTERLEAVED NO
MMAP_NONINTERLEAVED NO
MMAP_COMPLEX NO
RW_INTERLEAVED YES
RW_NONINTERLEAVED NO
Formats:
U8 YES
S16_LE YES
S16_BE YES
S32_LE YES
S32_BE YES
FLOAT_LE YES
FLOAT_BE YES
MU_LAW YES
A_LAW YES
Number of channels
min channels: 1
max channels: 32
1 channels YES
2 channels YES
3 channels YES
4 channels YES
5 channels YES
6 channels YES
7 channels YES
8 channels YES
9 channels YES
10 channels YES
11 channels YES
12 channels YES
13 channels YES
14 channels YES
15 channels YES
16 channels YES
Sample Rates:
min rate: 1 (dir = 0)
max rate: 192000 (dir = 0)
8000 YES
16000 YES
22050 YES
32000 YES
44100 YES
48000 YES
96000 YES
192000 YES
audio_alsa_source[pulse]: using S32_LE
audio_alsa_source[pulse]: sample resolution = 32 bits
----------8<--------------

M. Hartje

Dr.-Ing. Michael H.
Labor Hochspannungstechnik / Labor elektrische Messtechnik
Neustadtswall 30; D-28199 Bremen
Germany

2

Hi Michael,

Unfortunately I do not have any good answers to your questions, but I
have added some comments below that might help.

On Wed, Sep 1, 2010 at 12:09 PM, Michael H.
[email protected] wrote:

Opensuse 11.3 uses pulseaudio as a standard audio-io. Gnuradio 3.3.x
offers alsa audiosink and audiosource.

I believe all linux distributions have been using pulseaudio for many
years now, but pulseaudio is built on top of alsa drivers so we have
both systems.

When I put “pulse” as parameter for the “device_name” in GRC, with
“verbose” in the “~/.gnuradio/config.conf” I got information about
samplerate and other parameters (see below) – in my case: the format
S32LE is selected. – How can I change to use S16LE?

Can you actually get usable audio in and out when you use “pulse” for
device? I use Ubuntu 9.10 and 10.04 and none of my computers are able
to work with that setting. 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.

How can I change these audio parameters in GRC? What other parameters
can be changed in ~/.gnuradio/config.conf or by call?
I like to reduce the audio samplerate down to 1000 Hz or up to 192 kHz
– is there any limit to do this when the hardware supports it?

The sample rate in GNU Radio is a parameter for the audio source and
sink - I think you can enter any value there.
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.

Alex