Difference between revisions of "Squeezeslave on the core"
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[[Category: Tutorials]] | [[Category: Tutorials]] | ||
+ | [[Category:Audio]] | ||
{| align="right" | {| align="right" | ||
| __TOC__ | | __TOC__ | ||
|} | |} | ||
==Whats does it do?== | ==Whats does it do?== | ||
− | Squeezeslave basically makes it possible to add additional 'virtual' Squeezeboxes to your Core or MD's just by adding additional sound-cards. Each Squeezeslave/Sound-card combo uses about 4-5% CPU on an ATOM/Ion based MD. We have tested an ATOM/Ion based MD running 3 x Squeezeslave/Sound-Card combo's while playing a ripped DVD from the Core without any problems at all. Using Squeezeslave/Sound-Card combo's makes it possible to have several independent audio outputs from your Core or from an MD allowing you to use the 2nd Zone of your Surround Amp for example to provide audio to adjoining room eg bathroom or maybe a kitchen. All of this expands the options you have when designing your system gives you enormous additional flexibility to locate additional audio sources where you need them and | + | Squeezeslave basically makes it possible to add additional 'virtual' Squeezeboxes to your Core or MD's just by adding additional sound-cards. Each Squeezeslave/Sound-card combo uses about 4-5% CPU on an ATOM/Ion based MD. We have tested an ATOM/Ion based MD running 3 x Squeezeslave/Sound-Card combo's while playing a ripped DVD from the Core without any problems at all. Using Squeezeslave/Sound-Card combo's makes it possible to have several independent audio outputs from your Core or from an MD allowing you to use the 2nd Zone of your Surround Amp for example to provide audio to an adjoining room eg a bathroom or maybe a kitchen. All of this expands the options you have when designing your system, gives you enormous additional flexibility to locate additional audio sources where you need them, and reduces the energy footprint of your system at the same time (in comparison to adding additional physical Squeezeboxes). |
==Squeezeslave Setup== | ==Squeezeslave Setup== | ||
Line 13: | Line 14: | ||
Many other brands of USB Audio adapter will probably work too. Please add your experiences with other working hardware here too. | Many other brands of USB Audio adapter will probably work too. Please add your experiences with other working hardware here too. | ||
+ | |||
+ | Under LinuxMCE 0810 it may be necessary to downgrade Alsa in order for the device to appear (in 'aplay -l' or 'squeezeslave -L'). Be aware that downgrading alsa will remove audio over hdmi capabilities on the affected computer. | ||
===Setting Up Squeezeslave on your Core or MD's=== | ===Setting Up Squeezeslave on your Core or MD's=== | ||
Line 25: | Line 28: | ||
sudo apt-get install subversion | sudo apt-get install subversion | ||
sudo apt-get install libasound2-dev | sudo apt-get install libasound2-dev | ||
+ | Since squeezeslave is only updating the display versions of their makefiles also needed for building | ||
+ | sudo apt-get install libncurses5-dev | ||
+ | sudo apt-get install liblircclient-dev | ||
+ | |||
+ | ===Squeezeslave is available in the debs=== | ||
+ | Easiest for anybody will be | ||
+ | sudo apt-get install squeezeslave | ||
+ | This will install squeezeslave in the right directory for you to use. If you want to build it yourself follow the next steps. | ||
+ | |||
===Typical build=== | ===Typical build=== | ||
svn checkout http://squeezeslave.googlecode.com/svn/squeezeslave/trunk/squeezeslave | svn checkout http://squeezeslave.googlecode.com/svn/squeezeslave/trunk/squeezeslave | ||
cd squeezeslave | cd squeezeslave | ||
− | make -f | + | make -f makefile.linux26-alsa-display realclean |
− | make -f | + | make -f makefile.linux26-alsa-display |
+ | |||
===Or Download Source / look at the squeezeslave wiki=== | ===Or Download Source / look at the squeezeslave wiki=== | ||
− | Download a version of [http://sourceforge.net/project/showfiles.php?group_id=105169 Squeezeslave]. I'm running the latest version which was 0.9- | + | Download a version of [http://sourceforge.net/project/showfiles.php?group_id=105169 Squeezeslave]. I'm running the latest version which was 0.9-173 |
Look at the slimdevices wiki for the latest options and install instructions http://wiki.slimdevices.com/index.php/SqueezeSlave | Look at the slimdevices wiki for the latest options and install instructions http://wiki.slimdevices.com/index.php/SqueezeSlave | ||
+ | |||
===Installing=== | ===Installing=== | ||
− | *You'll want to put it somewhere in your path. | + | *You'll want to put it somewhere in your path. (This is already done if you did the apt-get install method) |
*There will be a file in the /bin directory called squeezeslave (there might be something added to this to represent the version you build, just rename the file to squeezeslave and copy to your wanted directory | *There will be a file in the /bin directory called squeezeslave (there might be something added to this to represent the version you build, just rename the file to squeezeslave and copy to your wanted directory | ||
− | *Example: /usr | + | *Example: /usr/bin |
====Modify /etc/rc.local==== | ====Modify /etc/rc.local==== | ||
Next add the following to /etc/rc.local | Next add the following to /etc/rc.local | ||
If your setting up Squeezeslave on your Core then use; | If your setting up Squeezeslave on your Core then use; | ||
− | /usr | + | /usr/bin/squeezeslave -o4 -m00:00:00:00:00:01 -r5 -M/var/log/squeezeslave.log |
If your setting up Squeezeslave on one of your MD's then use; | If your setting up Squeezeslave on one of your MD's then use; | ||
− | /usr | + | /usr/bin/squeezeslave -o4 192.168.80.1 -m00:00:00:00:00:01 -r5 -M/var/log/squeezeslave.log |
* the IP address should be the IP address of your Core (**Only needed if your running Squeezeslave on MD's**). | * the IP address should be the IP address of your Core (**Only needed if your running Squeezeslave on MD's**). | ||
* the MAC address can be whatever you want, it just needs to be the same as the device created in linux mce | * the MAC address can be whatever you want, it just needs to be the same as the device created in linux mce | ||
− | * the -o option specifies which | + | * the -o option specifies which output device ie /dev/dsp1 (check with "squeezeslave -L" for available devices then use '-oN' where 'N' is the number next to your output device) |
See example output using 'squeezeslave -L' below; | See example output using 'squeezeslave -L' below; | ||
− | + | <pre>Output devices: | |
− | + | 0: (ALSA) SB Live! Value [CT4832]: ADC Capture/Standard PCM Playback (hw:0,0) (11/46) | |
− | + | 2: (ALSA) SB Live! Value [CT4832]: Multichannel Capture/PT Playback (hw:0,2) (10/42) | |
− | + | 3: (ALSA) SB Live! Value [CT4832]: Multichannel Playback (hw:0,3) (10/42) | |
− | + | 4: (ALSA) USB Audio Device: USB Audio (hw:1,0) (10/42) | |
− | + | 5: (ALSA) front (11/46) | |
− | + | 6: (ALSA) rear (11/46) | |
− | + | 7: (ALSA) center_lfe (11/46) | |
− | + | 8: (ALSA) surround40 (11/46) | |
− | + | 9: (ALSA) surround41 (11/46) | |
− | + | 10: (ALSA) surround50 (11/46) | |
− | + | 11: (ALSA) surround51 (11/46) | |
− | + | 12: (ALSA) iec958 (10/42) | |
− | + | 13: (ALSA) spdif (10/42) | |
− | + | 14: (ALSA) spdif_playback (11/46) | |
+ | 15: (ALSA) asym_spdif (11/46) | ||
+ | 17: (ALSA) asym_analog (42/46) | ||
+ | 18: (ALSA) usb_analog (42/46) | ||
+ | 19: (ALSA) dmix (42/42) | ||
+ | *20: (ALSA) default (42/46)</pre> | ||
− | I am using the No. | + | |
+ | I am using the No.18 device in the output above and therefore would use '-o18' switch when using the squeezeslave command. | ||
* the -r option tells squeezeslave to keep retrying to connect to the server, useful if the server is not running yet. | * the -r option tells squeezeslave to keep retrying to connect to the server, useful if the server is not running yet. | ||
* the -M option makes it run as a Daemon and creates log | * the -M option makes it run as a Daemon and creates log | ||
+ | |||
+ | ====Fixing sample rate issues==== | ||
+ | Squeezeslave only likes the 44.1 kHz sample rate. Anything lower will sounds like the Smurfs, anything higher will sound "slow". This is fixed by converting the source stream to something squeezeslave can cope with. | ||
+ | |||
+ | You need to edit the <i>/etc/squeezeboxserver/convert.conf</i> file so it has these lines in it: | ||
+ | |||
+ | mp3 flc squeezeslave * | ||
+ | [sox] -q -t mp3 $FILE$ -t flac -C 0 -r 44100 - | ||
+ | aac flc squeezeslave * | ||
+ | [faad] -q -w -f 1 $FILE$ | [flac] -cs --totally-silent --compression-level-0 --ignore-chunk-sizes - | [sox] -q -t flac - -t flac -C 0 -b 16 -r 44100 - | ||
+ | |||
+ | The aac to flc conversion could be shorter, but sox has a problem with '-t wav' with the output of faad and outputs an empty stream, and flac won't actually resample the stream when the --sample-rate=44100 parameter is given to it. | ||
+ | |||
+ | More conversions might be necessary as new stations are found to be problematic, but the strategy is the same: Convert to 'flac', resample to 44100 Hz. | ||
+ | |||
+ | You'll have to restart Squeezebox Server (Logitech Media Server) for the change to take effect. | ||
===Setting Up Alsamixer=== | ===Setting Up Alsamixer=== | ||
Line 79: | Line 115: | ||
===Setting Up LinuxMCE=== | ===Setting Up LinuxMCE=== | ||
− | Next step, manually add the squeezeslave to linuxmce as a squeezebox using the mac address you gave it. | + | Next step, manually add the squeezeslave to linuxmce as a squeezebox using the mac address you gave it. The squeezebox player can be assigned to a room/entertainment area without an MD, in fact this would be a typical installation. |
====Select Device==== | ====Select Device==== | ||
− | * Select ''' | + | * Select '''Wizard->Devices->A/V Equipment''' and press 'Add device' on the bottom of the page. |
− | * | + | * In the Device Template dropdown select 'SqueezeBox Player' (template #58) and press 'Pick device template'. |
− | * Assign it to a room and | + | * Assign it to a room in the left dropdown box (-select room-, make sure you select a room that does not yet have a MD in it!), put the MAC of the squeezeslave in the MAC entry field and press update. |
* Regen your orbiters and reload the router. | * Regen your orbiters and reload the router. | ||
Restart the core to make sure it's starting automatically, to run it manually just run the line made in the rc.local | Restart the core to make sure it's starting automatically, to run it manually just run the line made in the rc.local | ||
− | /usr | + | /usr/bin/squeezeslave -o5 -m 00:00:00:00:00:01 -r5 -M/var/log/squeezeslave.log |
* Check with ps if it is running: | * Check with ps if it is running: | ||
ps aux | grep squeezeslave | ps aux | grep squeezeslave | ||
**Example output: | **Example output: | ||
− | root 11502 0.0 0.8 51484 8812 ? SLl Apr07 0:33 /usr | + | root 11502 0.0 0.8 51484 8812 ? SLl Apr07 0:33 /usr/bin/squeezeslave -05 -m00:00:00:00:00:02 -r5 -M/var/log/squeezeslave |
That should do it. | That should do it. | ||
− | use /usr | + | use /usr/bin/squeezeslave -L for available audio devices |
− | use /usr | + | use /usr/bin/squeezeslave -h for a list of options (see below) |
− | <pre>/usr | + | <pre>/usr/bin/squeezeslave -h |
squeezeslave 0.9-143 | squeezeslave 0.9-143 | ||
compile flags: linux portaudio:1485 debug signals daemon | compile flags: linux portaudio:1485 debug signals daemon | ||
Line 193: | Line 229: | ||
slimaudio_output | slimaudio_output | ||
slimaudio_output_v</pre> | slimaudio_output_v</pre> | ||
+ | |||
+ | ==Troubleshooting== | ||
+ | |||
+ | If you use a USB audio card and squeezeslave gives you an error, try the following | ||
+ | |||
+ | First of all make sure you are running the latest version. | ||
+ | |||
+ | Edit your /etc/asound.conf and add the following | ||
+ | |||
+ | <pre>pcm.usb_analog { | ||
+ | type asym | ||
+ | playback.pcm "plug:dmix:1" | ||
+ | capture.pcm "plughw:1" | ||
+ | }</pre> | ||
+ | |||
+ | After this restart alsa | ||
+ | |||
+ | /etc/init.d/alsa-utils restart | ||
+ | |||
+ | check your alsamixer to make sure pcm is unmuted and on a good level | ||
+ | |||
+ | Try squeezeslave again | ||
+ | == Information from other places == | ||
+ | The slimdevices forum has a nice [http://forums.slimdevices.com/showthread.php?86253-Poor-Man-s-Multiroom-Audio post] on how to setup multiple Squeezeslave zones with a single soundcard. | ||
+ | |||
+ | In case the above link does not work anymore, there is a [http://deb.linuxmce.org/PoorMansMultiroomAudio.pdf PDF] output of said forum entry available. |
Latest revision as of 16:44, 16 January 2013
Contents
|
Whats does it do?
Squeezeslave basically makes it possible to add additional 'virtual' Squeezeboxes to your Core or MD's just by adding additional sound-cards. Each Squeezeslave/Sound-card combo uses about 4-5% CPU on an ATOM/Ion based MD. We have tested an ATOM/Ion based MD running 3 x Squeezeslave/Sound-Card combo's while playing a ripped DVD from the Core without any problems at all. Using Squeezeslave/Sound-Card combo's makes it possible to have several independent audio outputs from your Core or from an MD allowing you to use the 2nd Zone of your Surround Amp for example to provide audio to an adjoining room eg a bathroom or maybe a kitchen. All of this expands the options you have when designing your system, gives you enormous additional flexibility to locate additional audio sources where you need them, and reduces the energy footprint of your system at the same time (in comparison to adding additional physical Squeezeboxes).
Squeezeslave Setup
Here's how to setup squeezeslave to run on your core or in fact any of your MD's. It's fairly straight forward but currently requires manual config/install of each Squeezeslave - I'm working on making this something you can just configure from Web Admin simply and quickly. One small issue is that because squeezeslave uses the OSS interface, you will need a separate sound card for each instance of squeezeslave you want to run.
Hardware Supported
The Startech Virtual 7.1 USB Audio Adapter (model No. ICUSBAUD107) works fine. This tiny USB Stick style adapter works perfectly under 7.10, 9.10 & 10.04. No installation...just plug it in and its ready a few secs later. Only stereo out jack and Mic input jack.
Many other brands of USB Audio adapter will probably work too. Please add your experiences with other working hardware here too.
Under LinuxMCE 0810 it may be necessary to downgrade Alsa in order for the device to appear (in 'aplay -l' or 'squeezeslave -L'). Be aware that downgrading alsa will remove audio over hdmi capabilities on the affected computer.
Setting Up Squeezeslave on your Core or MD's
If you want to setup Squeezeslave on your Core then either open Konsole session from the KDE Desktop or ssh in from another machine and sudo yourself. If you want to set up Squeezeslave on an MD then ssh into your Core and then use;
ssh moonNNN (**where NNN is the ID number of the MD you want to ssh into.)
You can find the ID of your MD from the Web Admin page at Wizard->Devices->Media Directors and the ID is the number with a '#' in front of it at the top of each MD section. Now follow the instructions below for each MD you want to add Squeezeslave too.
Needed Dependencies
System libraries needed are subversion and libasound2-dev
sudo apt-get install subversion sudo apt-get install libasound2-dev
Since squeezeslave is only updating the display versions of their makefiles also needed for building
sudo apt-get install libncurses5-dev sudo apt-get install liblircclient-dev
Squeezeslave is available in the debs
Easiest for anybody will be
sudo apt-get install squeezeslave
This will install squeezeslave in the right directory for you to use. If you want to build it yourself follow the next steps.
Typical build
svn checkout http://squeezeslave.googlecode.com/svn/squeezeslave/trunk/squeezeslave cd squeezeslave make -f makefile.linux26-alsa-display realclean make -f makefile.linux26-alsa-display
Or Download Source / look at the squeezeslave wiki
Download a version of Squeezeslave. I'm running the latest version which was 0.9-173
Look at the slimdevices wiki for the latest options and install instructions http://wiki.slimdevices.com/index.php/SqueezeSlave
Installing
- You'll want to put it somewhere in your path. (This is already done if you did the apt-get install method)
- There will be a file in the /bin directory called squeezeslave (there might be something added to this to represent the version you build, just rename the file to squeezeslave and copy to your wanted directory
- Example: /usr/bin
Modify /etc/rc.local
Next add the following to /etc/rc.local
If your setting up Squeezeslave on your Core then use;
/usr/bin/squeezeslave -o4 -m00:00:00:00:00:01 -r5 -M/var/log/squeezeslave.log
If your setting up Squeezeslave on one of your MD's then use;
/usr/bin/squeezeslave -o4 192.168.80.1 -m00:00:00:00:00:01 -r5 -M/var/log/squeezeslave.log
- the IP address should be the IP address of your Core (**Only needed if your running Squeezeslave on MD's**).
- the MAC address can be whatever you want, it just needs to be the same as the device created in linux mce
- the -o option specifies which output device ie /dev/dsp1 (check with "squeezeslave -L" for available devices then use '-oN' where 'N' is the number next to your output device)
See example output using 'squeezeslave -L' below;
Output devices: 0: (ALSA) SB Live! Value [CT4832]: ADC Capture/Standard PCM Playback (hw:0,0) (11/46) 2: (ALSA) SB Live! Value [CT4832]: Multichannel Capture/PT Playback (hw:0,2) (10/42) 3: (ALSA) SB Live! Value [CT4832]: Multichannel Playback (hw:0,3) (10/42) 4: (ALSA) USB Audio Device: USB Audio (hw:1,0) (10/42) 5: (ALSA) front (11/46) 6: (ALSA) rear (11/46) 7: (ALSA) center_lfe (11/46) 8: (ALSA) surround40 (11/46) 9: (ALSA) surround41 (11/46) 10: (ALSA) surround50 (11/46) 11: (ALSA) surround51 (11/46) 12: (ALSA) iec958 (10/42) 13: (ALSA) spdif (10/42) 14: (ALSA) spdif_playback (11/46) 15: (ALSA) asym_spdif (11/46) 17: (ALSA) asym_analog (42/46) 18: (ALSA) usb_analog (42/46) 19: (ALSA) dmix (42/42) *20: (ALSA) default (42/46)
I am using the No.18 device in the output above and therefore would use '-o18' switch when using the squeezeslave command.
- the -r option tells squeezeslave to keep retrying to connect to the server, useful if the server is not running yet.
- the -M option makes it run as a Daemon and creates log
Fixing sample rate issues
Squeezeslave only likes the 44.1 kHz sample rate. Anything lower will sounds like the Smurfs, anything higher will sound "slow". This is fixed by converting the source stream to something squeezeslave can cope with.
You need to edit the /etc/squeezeboxserver/convert.conf file so it has these lines in it:
mp3 flc squeezeslave * [sox] -q -t mp3 $FILE$ -t flac -C 0 -r 44100 - aac flc squeezeslave * [faad] -q -w -f 1 $FILE$ | [flac] -cs --totally-silent --compression-level-0 --ignore-chunk-sizes - | [sox] -q -t flac - -t flac -C 0 -b 16 -r 44100 -
The aac to flc conversion could be shorter, but sox has a problem with '-t wav' with the output of faad and outputs an empty stream, and flac won't actually resample the stream when the --sample-rate=44100 parameter is given to it.
More conversions might be necessary as new stations are found to be problematic, but the strategy is the same: Convert to 'flac', resample to 44100 Hz.
You'll have to restart Squeezebox Server (Logitech Media Server) for the change to take effect.
Setting Up Alsamixer
Next make sure all the volume levels in the mixer (alsamixer) are set correctly
alsamixer
Make sure that the settings are as desired and save (Esc button)
Setting Up LinuxMCE
Next step, manually add the squeezeslave to linuxmce as a squeezebox using the mac address you gave it. The squeezebox player can be assigned to a room/entertainment area without an MD, in fact this would be a typical installation.
Select Device
- Select Wizard->Devices->A/V Equipment and press 'Add device' on the bottom of the page.
- In the Device Template dropdown select 'SqueezeBox Player' (template #58) and press 'Pick device template'.
- Assign it to a room in the left dropdown box (-select room-, make sure you select a room that does not yet have a MD in it!), put the MAC of the squeezeslave in the MAC entry field and press update.
- Regen your orbiters and reload the router.
Restart the core to make sure it's starting automatically, to run it manually just run the line made in the rc.local
/usr/bin/squeezeslave -o5 -m 00:00:00:00:00:01 -r5 -M/var/log/squeezeslave.log
- Check with ps if it is running:
ps aux | grep squeezeslave
- Example output:
root 11502 0.0 0.8 51484 8812 ? SLl Apr07 0:33 /usr/bin/squeezeslave -05 -m00:00:00:00:00:02 -r5 -M/var/log/squeezeslave
That should do it.
use /usr/bin/squeezeslave -L for available audio devices
use /usr/bin/squeezeslave -h for a list of options (see below)
/usr/bin/squeezeslave -h squeezeslave 0.9-143 compile flags: linux portaudio:1485 debug signals daemon Squeezeslave is licensed free of charge. There is NO WARRANTY for the program. This program is provided "as is" without warranty of any kind, either expressed or implied, including, but not limited to, the implied warranties of merchantability and fitness for a particular purpose. The entire risk as to the quality and performance of the program is with you. Should the program prove defective, you assume the cost of all necessary servicing, repair or correction. Copyright (c) 2004-2007 Richard Titmuss, 2008-2010 Duane Paddock. squeezeslave [options] [<server address>] The Squeezebox Server address defaults to 127.0.0.1. Options: -h, --help: Prints this message. -a, Sets the amplitude of a high-frequency tone --predelay_amplitude <val>: produced during the predelay (see --predelay). The frequency is set at the source's sampling rate/2 and the amplitude is in absolute value. For 16-bit sources, the max is 32767, but values below 10 are likely to work. The goal is to produce an inaudible signal that will cause DACs to wake-up and lock before actual samples are played out. If the DAC locks using only silence, do not use this option (it will default to 0). -k, --keepalive <sec>: Controls how frequently squeezeslave sends a alive signal to SqueezeCenter. 6.5.x servers need this to avoid dropping the player's connection. By default, the implementation chooses the right value: 10s for a >=6.5.x server and 0s for a <6.5.x server, which means no keepalive. -M, --daemonize <logfile> Run squeezeslave as a daemon. Messages written to specified file. Not supported with lirc and display modes. -L, --list List available audio devices and exit. -m, --mac <mac_address>: Sets the mac address for this instance. Use the colon-separated notation. The default is 00:00:00:00:00:01. SqueezeCenter uses this value to distinguish multiple instances, allowing per-player settings. -o, --output <device_id>: Sets the output device id. The default id is 0. The output device ids can be found with -L. -P, --port <portnumber>: Sets the SqueezeCenter port number. The default port is 3483. -p, --predelay <msec>: Sets a delay before any playback is started. This is useful if the DAC used for output is slow to wake-up/lock, causing the first few samples to be dropped. --retry Causes the program to retry connecting to SqueezeCenter until it succeeds or is stopped using SIGTERM or keyboard entry (see -s/--signal). If the connection to SqueezeCenter is lost, the program will poll it until it restarts. --retry enables retry with a 5 second delay between attempts. -r <sec> For a different retry interval use -r and the desired interval in seconds. (ie. -r10) A value is required for this option. -s, --signal: Ignored. Always uses SIGTERM to exit. -V, --version: Prints the squeezeslave version. -v, --volume <sw|off>: Enables/disables volume changes done by SqueezeCenter during its operation, such as when changing the volume through the web interface or when applying replay gain. Defaults to sw. sw: volume changes performed in software. off: volume changes ignored. -Y, --debuglog <logfile>: Redirect debug output from stderr to <logfile>. -d, --debug <trace_name>: Turns on debug tracing for the specified level. The option can be used multiple times to enable multiple levels. Available levels: all slimproto slimaudio slimaudio_buffer slimaudio_buffer_v slimaudio_decoder slimaudio_decoder_r slimaudio_decoder_v slimaudio_http slimaudio_http_v slimaudio_output slimaudio_output_v
Troubleshooting
If you use a USB audio card and squeezeslave gives you an error, try the following
First of all make sure you are running the latest version.
Edit your /etc/asound.conf and add the following
pcm.usb_analog { type asym playback.pcm "plug:dmix:1" capture.pcm "plughw:1" }
After this restart alsa
/etc/init.d/alsa-utils restart
check your alsamixer to make sure pcm is unmuted and on a good level
Try squeezeslave again
Information from other places
The slimdevices forum has a nice post on how to setup multiple Squeezeslave zones with a single soundcard.
In case the above link does not work anymore, there is a PDF output of said forum entry available.