Uwe Hermann - Playing audio on the NSLU2 - Comments

soundcards

anacron — Tue, 07 Oct 2008 15:21:00 +0200

Thanks for really usefull article! you can get those same soundcards dirt cheap from dealextreme, 3.98 US dollars, free shipping!. I didn't know those work for linux, but thanks to you now I do

Unable to Play Streaming WMA/ASX Files with mplayer

meappy — Sat, 19 Jan 2008 21:48:20 +0100

Anyone experiencing extremely choppy audio while trying to play online ASX/WMA streams in mplayer?

Tried all sorts of solutions, from adjusting srate to tweaking -cache control in mplayer options, to no avail.

Would like to see some input from you guys.

Thanks!

OSS

Uwe Hermann — Sat, 19 Jan 2008 11:36:31 +0100

Nice, thanks for the OSS sound tip.

Uwe.

/dev/dsp (No such file or directory)

meappy — Sat, 19 Jan 2008 06:20:52 +0100

I was toying with the idea of purchasing a wireless radio receiver, when I had a light bulb moment, "Why not use my NSLU2 + Debian to play audio?" My Debian Slug has been serving me for about a year plus now, and attaching a USB Audio Device to it would have made it play online radio just as well. Brilliant!

So off I went, to the computer stores, bought myself the same USB Audio Device called "3D Sound" which you have. I have a full Debian running on my overclocked NSLU2.

What to do next? That's when I stumbled on your Blog

You're right that the USB Audio Device works out of the box on Debian 2.6.18-4-ixp4xx which is installed in my NSLU2

For people who plan to use this similar USB Audio Device and run into an error like /dev/dsp (No such file or directory) while trying to play audio, that's because this device uses ALSA drivers

mplayer and madplay search for /dev/dsp which is what OSS programs use

The following modules will have to be loaded for backward compatibility with OSS (Open Sound System) programs, ALSA uses /dev/snd/* devices.

modprobe snd-pcm-oss
modprobe snd-mixer-oss

Reference: http://tldp.org/HOWTO/Alsa-sound-2.html

That's it!

Works like charm :)

Thanks for the write up Uwe, nice read on the various players that work.

My experience

Antemaro — Fri, 13 Jul 2007 07:12:14 +0200

Hi !

I'm myself trying to configure my Turboslug to do lot of things, which include a music server. I'm writing down all the stuff I'm doing, to publish later on the webserver that is supposed to run on it (not yet online, that's why my webpage says "Forbidden access").

I work on the music part for the moment. My system is a Debian Etch 4.0r0 for now, and MPD runs fine, but only for MP3 and FLAC files. Ogg files (320kpbs I admit) takes up 98%+ of the CPU and are inaudible.

For MP3s (320kpbs also) it plays at ~7%, better than Mr Hermann it seems. Same for the FLACs, around 8-9%.

I will try to install the tremor decoder for ogg, and recompile mpd to use it. But I need to switch to testing for it... Or use a backport. I don't know yet.

I hope this will be useful to you.

Hm, I didn't notice mixer

Uwe Hermann — Thu, 12 Jul 2007 21:37:00 +0200

Hm, I didn't notice mixer problems or overdriving problems the last time I tried. I used both passive and active speakers with good success.

Uwe.

USB Audio working how well?

Marco Cogoni — Tue, 10 Jul 2007 18:10:27 +0200

hi, very interesting article.
I have exactly the same device as yours as usb audio card but
I have a problem with the mixer... it does not work!
The problem is that connecting to a pair of amplified speakers
it overdrives them and the only solution is to use software mixing but
it reduces audio quality.
Do you have the same problem?

Thanks.

The article is very good

wltuoye — Tue, 03 Jul 2007 02:58:20 +0200

The article is very good

save flash life

Stephen — Sat, 02 Jun 2007 10:41:04 +0200

On some (Unslung?) wiki page, I found a recommendation to make /var/log a ramdisk. Since it only said how to copy /var/log to memory but not back (which might be important), here's mine:

#!/bin/sh
# /etc/init.d/mount_var.sh
# Script section to create ramdisk for /var

# disable the oom-killer to use the full swap
/sbin/sysctl -w vm.overcommit_memory=1
# From JNC : this command does not exist on my slug (release 2.7)

# better only use /var/log then the full /var
# following lines might need to be adjusted according to your OS and/or installed services
/bin/echo "Creating ramfs for /var/log:"
/bin/mkdir -p /var/oldlog
/bin/mount -t ramfs ramfs /mnt -o maxsize=256
/bin/cp -rp /var/log/* /mnt/
/bin/mount -o bind /var/log /var/oldlog
/bin/mount -o bind /mnt /var/log
/bin/umount /mnt
return 1

and:

#!/bin/sh
# /etc/init.d/umount_var.sh
# Script section to destroy ramdisk for /var

/bin/echo "Destroying ramfs for /var/log:"
#/bin/cp -rp /var/log/* /var/oldlog
/usr/bin/rsync -au /var/log/. /var/oldlog/.
/bin/umount /var/log
/bin/umount /var/oldlog
return 1

Together with these links
lrwxrwxrwx 1 root root 23 May 21 16:35 ../rc0.d/S37umount_var.sh -> ../init.d/umount_var.sh
lrwxrwxrwx 1 root root 23 May 21 16:36 ../rc6.d/S37umount_var.sh -> ../init.d/umount_var.sh
lrwxrwxrwx 1 root root 22 May 21 15:34 ../rcS.d/S37mount_var.sh -> ../init.d/mount_var.sh
I suppose disk write access will be limited to software installs (and some swap, since ramdisk old contents will overflow to swap I suppose)

Suggestions welcome.

mpd

Uwe Hermann — Tue, 15 May 2007 22:54:15 +0200

Should run pretty good, lots of people seem to be using it (I haven't tried yet, don't need it). There's a good page in the NSLU2-Linux wiki on that...

HTH, Uwe.

Mplayer

Uwe Hermann — Tue, 15 May 2007 22:52:24 +0200

Yep, true. This is not compiled in the standard mplayer Debian package, though (maybe worth a wishlist bug report)...

Vorbis, Tremor

Uwe Hermann — Tue, 15 May 2007 22:51:02 +0200

The "normal" ogg123 is floiting point, thus slow. The tiny program (ivorbisfile_example) uses "Tremor" which is a fixed-point version of the code and works fine (or at least better).

There's no Tremor support in ogg123 Debian package (yet), as far as I know.

Fixed Point?

mentor — Tue, 15 May 2007 21:07:57 +0200

Is that Vorbis decoder the floating point or fixed point version. (I ask this with the understanding that floating point is software emulated by the kernel on ARM processors that don't have some form of FPU).

fixed-point decoders

Anonymous — Mon, 14 May 2007 17:01:59 +0200

You should compile mplayer with tremor and libmad and configure it to use those. Then mplayer should work.

Please do expand on the

Anonymous — Mon, 14 May 2007 13:49:32 +0200

Please do expand on the "implemented [...] measures to maximize the life time of the USB thumb drive". I'd think that it is pretty hard to destroy a flash drive, see the article about swap space on flash drives at Dan's Data.
Regardless of that I'd think that after the garanty on these things (5 or 10 year mostly) runs out, the replacement would would cost almost nothing (Moore's Law).

Playing audio on the NSLU2

Uwe Hermann — Mon, 14 May 2007 03:01:42 +0200

I'm a happy NSLU2 user since a few months now, and I'm using it for all kinds of things, e.g. as a 24/7 remote ssh server at home (using DynDNS and the ddclient Debian package), as IRC logger (screen + irssi), etc. etc.

I was considering multiple options as to where/how to install the slug (USB thumb drive, Compact Flash, disk drive, ...) but I settled with a full Debian install on an 1 GB USB thumb drive for now. I implemented some measures to maximize the life time of the USB thumb drive, maybe I'll post some info on that later...

One new thing I've been trying lately is to use the slug as an audio player.

As it doesn't come with an integrated sound card, you have to use an external USB audio device. I've got mine (see photo) from eBay for ca. 5 Euro (+ shipping) and it works out of the box with Linux 2.6.18 using the snd_usb_audio kernel module. You simply attach it via USB (the module is automatically loaded) and then attach external speakers to it. Here's an lsusb of the device:

Bus 001 Device 011: ID 1130:f211 Tenx Technology, Inc.

One problem with playing audio on the slug is the slow CPU. At 266 MHz (and without FPU!) playing audio with "normal" audio players such as mplayer or mpg321 is not possible. But there are several ways to make the slug play your favorite music. Here's a list of players I tested and a status report of whether they work at all. If yes, I listed a rough percentage of CPU load resulting from playing the music.

MP3:
- mplayer, mpg321, aplay, playsound, and splay don't work.
- $ madplay foo.mp3: 17% CPU load

Ogg vorbis:

mplayer, aplay, playsound, and ogg123 don't work.

$ apt-get install libvorbisidec-dev
$ cd /usr/share/doc/libvorbisidec-dev/examples
$ make
$ cat foo.ogg | ./ivorbisfile_example | aplay -f cd

Result: 40% CPU load

MOD, XM, S3M, IT, etc.:
- $ mikmod foo.mod: 10% CPU load (even with compressed MOD files)
WAV:
- $ mplayer foo.wav: 10% CPU load
- $ aplay foo.wav: 10% CPU load
- $ playsound foo.wav: 10% CPU load
FLAC:
- $ flac123 foo.flac: 17% CPU load
SPEEX:
- $ speexdec foo.spx: doesn't work, 100% CPU load. Any known alternatives?
AU:
- $ cat foo.au > /dev/dsp: 3% CPU load (but sounds crappy)
- $ cat foo.au > /dev/audio: 3% CPU load (sounds better)
- $ mplayer foo.au: 5% CPU load
- $ aplay foo.au: 5% CPU load
- $ playsound foo.au: 5% CPU load
AIFF:
- $ sox foo.aiff -t wav - | aplay: 50% CPU load (a bit stupid, but it works)
Streaming MP3:
- $ mplayer http://www.example.com/foo.mp3: doesn't work, 100% CPU load.
- $ wget http://www.example.com/foo.mp3 -O - | madplay - : 17% CPU load
Streaming Ogg Vorbis:
- $ cd /usr/share/doc/libvorbisidec-dev/examples $ wget http://www.example.com/foo.ogg -O - | ./ivorbisfile_example | aplay -f cd: 40% CPU load

The SlugAsAudioPlayer page in the NSLU2-Linux wiki might have further information on this topic.

Feel free to add comments if you know of other audio types which can be played on an NSLU2.