Problem with Alsa

Question

Hello,
I have got a problem with my asoundrc.. The problem is the lowpass filter with the subwoofer. It gets all frequencies. I've tried different soulutions from different forums witth different asoundrc. config codes. But nothing of them worked. Another hint is the thing, that the upmix from a stereo source to 5.1 worked out of the box with my soundcard. And when I now try to fill the asoundrc. there is no change or if it's the default device sometimes an error message. But it all seems to be unchanged when I edit it.
Thank you!
OS: Arch Linux 64 bit / KDE (removed gnome again)
Soundcard: Creative Audigy 2 / Alsa Driver
One source of an asound.conf:
http://alsa.opensrc.org/Low-pass_filter … 28HOWTO%29

Answer 1

Okay, Unless I have the asoundrc empty there is upmixed 5.1 sound "out of the box". But I have tried this configuration
pcm.upmix_20to51 {
type plug
slave.pcm lowpass_21to21
slave.channels 3
ttable {
0.0 1 # left channel
1.1 1 # right channel
0.2 0.5 # mix left and right ...
1.2 0.5 # ... channel for subwoofer
pcm.lowpass_21to21 {
type ladspa
slave.pcm upmix_21to51
path "/usr/lib/ladspa"
channels 3
plugins {
0 {
id 1098 # Identity (Audio) (1098/identity_audio)
policy duplicate
input.bindings.0 "Input";
output.bindings.0 "Output";
1 {
id 1672 # 4 Pole Low-Pass Filter with Resonance (FCRCIA) (1672/lp4pole_fcrcia_oa)
policy none
input.bindings.2 "Input";
output.bindings.2 "Output";
input {
controls [ 300 2 ]
pcm.upmix_21to51 {
type plug
slave.pcm surround51
slave.channels 6
ttable {
0.0 1 # front left
1.1 1 # front right
0.2 1 # rear left
1.3 1 # rear right
0.4 0.5 # center
1.4 0.5 # center
2.5 1 # subwoofer
But still no lowpass filter
I also tried this configuration:
# ALSA configuration for use with surround speaker sets.
# Provides on-demand upmixing via plugin plus
# lowpass filtering/crossover capability plus
# software-mixing/dmix support.
# Possibly useful sources include:
# https://wiki.archlinux.org/index.php/Alsa
# http://www.volkerschatz.com/noise/alsa.html
# http://www.sabi.co.uk/Notes/linuxSoundALSA.html
# http://www.alsa-project.org/alsa-doc/alsa-lib/pcm_plugins.html
# For those who understand German: http://wiki.ubuntuusers.de/.asoundrc
# Change default samplerate conversion algorithm to
# SRC_SINC_MEDIUM_QUALITY. Requires package "libsamplerate".
# See http://www.mega-nerd.com/SRC/api_misc.html.
# Other resampling algorithms are available.
defaults.pcm.rate_converter "samplerate_medium"
# The first ALSA device of the first soundcard
# (here: Analog Multichannel Ouput).
# See /proc/asound and "aplay -l".
pcm.sndcard {
type hw
card 0
device 0
# Dmix software mixing device.
# Takes multiple input streams, resamples them to target
# rate (here: 48kHz) and sends it to the sound card.
pcm.dmix51 {
type dmix
ipc_key 1024
slave {
pcm "sndcard"
channels 6
rate 48000
period_time 0 # Fixes audio crackling/stutter
period_size 1024 # with libsamplerate and chromium.
buffer_time 0 # Not all options may be
buffer_size 4096 # absolutely necessary.
# Convert float data from "lowpass51" to integer data
# and pass it on to the dmix device.
pcm.lowpass_float {
type lfloat
slave {
pcm "dmix51"
format "S16_LE"
# Lowpass filter.
# Requires "ladspa" for plugin support,
# "cmt" for identity_audio plugin and
# "swh-plugins" for lpf plugin.
# See http://www.ladspa.org/.
pcm.lowpass51 {
type ladspa
slave.pcm "lowpass_float"
path "/usr/lib/ladspa"
plugins {
# Copies all audio of all channels to other plugins.
# If no other plugin handles a channel, it comes out unchanged.
0 {
id 1098 # Identity (Audio) (1098/identity_audio)
policy duplicate
input.bindings.0 "Input";
output.bindings.0 "Output";
# Actual low-pass filter functionality.
# Operate on channel 5 (LFE) and remove
# frequencies higher than 120Hz.
1 {
id 1051 # Low Pass Filter (One Pole) (1051/lpf)
policy none
input.bindings.5 "Input";
output.bindings.5 "Output";
input {
controls [ 120 ]
# Automatic upmixing. Requires package "alsa-plugins".
pcm.upmix51 {
type upmix
# Simply "lowpass51" won't work.
# "plug:..." specifies a plug device like
# the long form for the default device below
# and takes care of channel/format conversions
# automatically.
slave.pcm "plug:lowpass51"
# Specifying the number of channels to upmix to here is mandatory.
channels 6
# Default device to be used by all applications playing all sorts of sources.
# There's automatic upmixing for 2.0 sources and native playback of 5.1 sources.
# (possibly others as supported by the upmix plugin)
pcm.!default {
type plug
slave.pcm "upmix51"
But I think the problem is an other:
When I use this simple configuration, the lowpass filter works:
pcm.lowpass {
type ladspa
slave.pcm "plughw:0"
path "/usr/lib/ladspa"
plugins [ {
label lpf
input {
controls [ 150 ]
pcm.test {
type plug
slave.pcm "lowpass"
The problem is, that it's working on all channels
Last edited by Destroyer4000 (2013-11-10 10:51:07)