Introducing aloopd - the ALSA Loop Sound Server

Aka, who needs the stinking pulseaudio?


All over many years, I only had one soundcard in my machines. I configured it once, and there it went. No further tweaking was ever needed. If I needed alternate sound output - just plug in a headphone to the headphone jack. Nothing else was needed, ALSA takes care of everything.

When laptops started to support HDMI output, a problem arose. The HDMI output in effect was a second soundcard; so all these new-fangled laptops now had two soundcards. It was not a problem in itself, except that the kernel had no idea which was was to be the "default". Often times, the HDMI output was chosen as the default soundcard (over the "more correct" analog output jack), and since the laptop HDMI's port was not connected to anything, the result is an absolute silence when the user tried to play some audio apps.

To address this problem, Kirk invented Multiple-Sound-Card-Wizard (MSWC) to allow the user to choose which soundcard he/she wanted to use as the default. This settings was persisted over reboots, so the user only had to configure it once. MSCW was quickly adopted by Puppy Linux world, and its derivatives still lives on until today.

In Fatdog, MSCW was replaced with "" (FDS) - which worked exactly like the original MSCW except that it had more options and more features (e.g. equaliser, pre-amp, stereoswap, etc).

And then came bluetooth speakers. The FDS was updated to support these as well, so audio apps could route the audio to these speakers too. Now, unlike the analog out/HDMI selection, which was usually set only once and then never touched again, with bluetooth speakers one might want to connect to it one day, and disconnect and use the internal speaker the other day.

FDS supported this - but, after each changes, the audio app had to be restarted. If you're watching a video you had to quit the video player, make the change using FDS, and re-started. A bit annoying, but not too bad you only had to do it once a day.

And then came USB soundcards. That's okay, we could still ignore that. And then come USB headphones. These are headphones whose cables are permanently soldered to USB soundcards, the only way to make them make sound, is to connect their USB connections to USB ports and then run FDS to set the configuration.

This now means that over the course of the day, one might want/need to change the "default" soundcard many times - perhaps to route over the internal soundcard, then to bluetooth speakers/headset, then to USB headphones, etc ... FDS still works, but if one has to restart the audio app everything this happens, it starts to get more and more annoying.

The solution to avoid re-starting the audio apps is to use a "audio router", a middleman that takes the output from an audio app, and then send it to the correct destination (internal soundcard, bluetooth speakers, USB devices, etc). These "audio routing" function is done by a "sound server", of which pulseaudio is the most well know notorious example, but there are others too (JACK for real-time audio, older/defunct ones like EsoundD/ESD, aRts, etc).

All these sound servers suffer from the same problem: the applications must be explicitly programmed to use them. Apps that uses PulseAudio have to use PulseAudio API and link with PulseAudio libraries, same for JACK, and all the others too. And therein lies the problem.
1) If you don't have these libraries at run-time, the app goes kaput.
2) Even if you do, in case the "sound server" cannot run properly at run-time, you won't hear any sound.

And PulseAudio, while being the most popular soundserver in this decade (due to it being pushed down the throat on many distributions, just like systemd is), isn't exactly the most stable or the easiest one to configure. If you need proof, just use your favourite search engine and see how many questions there are about "PulseAudio not working" ...

Anyway, as I said, in days past, I only had one soundcard, so the need to do all these was non-existent - if one only has one soundcard, what's really the need of having a middleman? So, I was never bothered about this for long while ...

Until now. Recently got a USB headphone. With a regular headphone, you plug in the jack to the hole, and it all works (the sound on the laptop was turned off and redirected to the headphone). This was by the way done by the __hardware__ (the audio codec chip), there is no "sound server" in the kernel that does this.

However, things aren't the same with USB audio. As I said above, it is effectively a different soundcard, so FDS needs to be called to configure the app to use it, and then the audio app has to be restarted ...

And thus is born the ALSA Loop Sound Server.

The ALSA Loop Sound Server

As it turns out, ALSA has already come with a sound server of sorts.
It's primitive compared to others, but for me, it does the job fine enough.

My objective is only one: I want to be able to switch sound output without having to shutdown and restart the audio apps. I can live with the interruption during the switching, I can live with the fact that different soundcards have different mixer (volume) control etc (although this apparently can be automated as well - I haven't tried it).

The ALSA Sound Server consist of two components: the kernel module component called snd-aloop (ALSA Loopback module), and the user-space program called "alsaloop". ALSA Loopback module basically acts are virtual soundcard and acts are a "pipe" - audio data goes from one part, and out into another. "alsaloop" acts like a pump - it read data from one card, and output it to another.

The entire setup is conceptually simple:
- use snd-aloop to create a virtual soundcard and make it as the default output.
- run alsaloop, which reads audio from this virtual soundcard, and push it out the actual soundcard.

So the audio routing becomes like this:
app --> loopback virtual soundcard --> alsaloop --> actual soundcard.

But what have we achieve with this middle-man setup? Well, the magic of this setup is that even if "alsaloop" is not running, the audio app will continue to blissfully send its output - except that of course you hear no sound.

To hear any sound, run the "alsaloop" pump, and if you want to switch output, just kill alsaloop and re-start it with different output. Presto!

This implementation is available on Fatdog64 812.

It is capable of switching audio seamlessly between internal soundcards and bluetooth speakers, without restarting the sound apps.

Beyond Fatdog64 812

After the release of Fatdog64 812, I worked a little bit more on the ALSA Sound Server and it is now capable of delivering __network__ audio, using a neat package called "trx" (available in the Fatdog repository).

It is now possible to send audio over the network, and receive audio from the network. Using multicast, it possible to send a single stream to multiple listeners at once.

All using only ALSA (and trx).

This implementation will be available on next release of Fatdog, whenever that will be. If you are keen to test, you can always get the "tip" version of Fatdog, which gets updated whenever there is an interesting feature (or update).

Posted on 9 Dec 2021, 16:15 - Categories: Fatdog64 Linux
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Fatdog64 812 Final is released

The release candidate was released a little over 3 weeks ago. As the reports have dried up and and we have fixed all reported bugs, it's time to release Fatdog 812 Final.

There are two features in Final which wasn't there in RC (and thus, is considered experimental because it only received short testing time): Simple Bluetooth Manager, and ALSA Loop sound server.

There is nothing special about the overdue Bluetooth Manager, but I may write a little about the ALSA Loop sound server (aloopd) later.

Release notes here, announcement (and discussions) here.

Get it from the usual mirrors:,, or

Posted on 9 Nov 2021, 22:18 - Categories: Fatdog64 Linux
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Fatdog64 812 RC is released

Yeap, still here. Still alive and kickin'.

Just dropping by to let you know something that you've probably already known: that is Fatdog64 812 RC has been released.

Release notes here, announcement (and discussions) here.

Get it from the usual mirrors:,, or

Unfortunately we lost AARNET for the Australian folks.

Posted on 17 Oct 2021, 00:58 - Categories: Fatdog64 Linux
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Fatdog64 811 is released

Fatdog64 811 was released on 10 September 2020.

Release notes here, announcement here.

Get it from the usual mirrors:, aarnet,, or

Posted on 20 Sep 2020, 00:27 - Categories: Fatdog64 Linux
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New forum for Fatdog

Fatdog has, for years, since its inception, always been piggybacking on Puppy Linux forum. Firstly because of its obvious roots; also because we simply didn't have enough man power to run and police an independent forum ourselves.

As the previous blog entry indicates, however, John de Murga, the owner of the Puppy Linux forum, sadly passed away, and the original Puppy Linux forum went down (for a time).

Behind the scenes people are frantically working to bring it up, but there are also efforts to setup a replacement forums, including one by rockedge.

By now, both efforts have been fruitful: the old forum has been resurrected and the rockedge forum has flourished with old and new members (re-)joining it.

The stewards of Puppy Linux has decided that the old forum will continue in read-only mode as archives, while rockedge forum will take over as the new Puppy Linux forum.

Rockedge has graciously offered a section of the forum specifically for Fatdog, for which we are very grateful.

After some internal discussions, we have decided to take the offer and continue the tradition of piggybacking on Puppy Linux forum. All of Fatdog team members have now re-joined there as well.

For your reference:

The new forum address: (Fatdog posts will be in the Fatdog section)

The old (archived) forum (in case you need to review/check old postings for older version of Fatdogs): (Fatdog posts are in the Puppy Projects section)

We'll see you there in the new forum!

Posted on 19 Aug 2020, 14:31 - Categories: Fatdog64 Linux PuppyLinux
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Goodbye to a friend - John de Murga

John de Murga (aka John Murga) was the owner of the official Puppy Linux forum, formerly located in

If you use Fatdog64, you will know that we hosted our support threads on the same forum.

But my involvement with the Puppy Linux forum dates back well before then. I started browsing the forum when I was still a Windows user back in 2006; and joined in 2007 when I was converted into Puppy Linux user - and had been a regular on the forum ever since. Until the forum went down in early July 2020.


But in all my years being John's forum, I don't really know John Murga. Not personally. Never met him. Never spoke with him. Not even knowing how he looked like - well, not until a few days before I wrote this. Not through my fault though, I only know bits and pieces that he himself chose to share, for he himself claimed to be 'the man of mystery'.

He and his work, however, left an indelible mark on my life. It was such a simple work. Setting up an online forum. What was so difficult about it? Get a web-hosting site. Click a button, and you've got a forum and up running. Easy. Everyone can do it, right?

No. Not every one can do what John did.

The forum he set up was the forum where I spent lots of my past life on. Where I got help when I started and when I stumbled. Where I, eventually, helped others as I became proficient enough. Where I, unexpectedly, met and became friends with people in the real world.

All of these because he had the tenacity to keep the forum going for 15+ years; and let the forum to govern itself instead of strict policing found in many others. He even had the magnanimity to allow people to post links of competing projects and forums. This was one of the factors why so many people stayed on and the forum grew to become the melting pot of folks from all walks of life, sharing the same interest - Puppy Linux, and Linux in general.

So it was great shock and sadness that I learn of his passing recently in May 2020. I was even more stunned to know that he had left a young family - a daughter and twins who were born shortly after his passing. I have young children myself, I could not even begin to contemplate how it must have felt, to be left so soon, and so suddenly.

Nevertheless, I would like offer a prayer of hope for whom that John's family, that John had left a legacy that not many people could manage to do: to change the life of thousands, if not then ten thousands. John had left many friends that he himself probably didn't know. I was one of them, one among the thousands. For us, he is a hero. In every sense of the word.

Goodbye, John, and all blessings in your next journey.

You will be missed, but not forgotten.


Eulogy from 01micko, the current steward of Puppy Linux

Eulogy from Barry Kauler, the creator of Puppy Linux

Posted on 19 Jul 2020, 14:53 - Categories: Fatdog64 Linux PuppyLinux General
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Fatdog64 updates - behind the scenes

Fatdog64 was last released on 23 Jan. And although we have been quiet, it doesn't mean that things stopped. Things are still going in the background, bug fixing, adding features, etc.

Here are a few major things that has been going on, in no particular order.

1. Puppy Linux forum user ICPUG has indicated possible issues with Fatdog savefile residing on an NTFS partition, especially partition shared with Windows. This is due to the way Fatdog uses ntfs-3g: it runs with full permission control enabled. It makes NTFS behaves like POSIX filesystem and we can use it for save directory (not only save file), but on the other hand it makes Windows complain about not-granted access each time the partition needs to be accessed from Windows.

Based on this feedback, we have added "ntfsnoperm" boot parameter to disable that permission control. When this parameter is used, ntfs-3g is run without permission: it would behave just like FAT filesystem (all files and directories are owned by a given uid/gid specified at mount time). It would not be possible to use a save directory on NTFS, but at least the permission wouldn't be touched and Windows will stop complaining.

2. The same ICPUG also found an old bug related to the above: where the user "spot" would be unable to access a Downloads folder that has been relocated to a save partition if the save partition is NTFS. This has been fixed.

3. Fatdog has long supported btrfs. The kernel is built to support btrfs and we have the complete btrfs-progs included; and nominally we support having save directory on btrfs. But this does not actually work; because "aufs" - the unifying filesystem layer that we use to make the magic happen, does not support btrfs the way it supports other filesystem. For the techie: the problem is that aufs cannot have its xino file inside btrfs. It has to be somewhere else.

Thanks for our team member SFR (his Puppy Forum name), this was brought to attention and he shared a fix too. The fix was tested, worked on, and finally merged: now, save directory will work seamlessly on btrfs-formatted partition.

4. The original motivation for doing (3) above was actually to attempt to use a compressed filesystem. This has been a particular interest for me for years. The last time I explored this (a couple of years ago), btrfs wasn't mature enough and there was no other native writable filesystem with compression support. Sure, there were native filesystem with compression support - but they were all readonly (squashfs being the most popular one). Sure, a couple of FUSE filesystems support compression too (in fact it's their number one feature), but they were not actively maintained and being done in userspace, it was slow. I never got enough motivation to implement them properly with Fatdog.

Btrfs finally changed this equation. By now it should be considered mature enough (although probably not as hyped as before), and it supports compression as well. In fact, it supports three different compression algorithms: lzo, lz4 and zstd.

So as we fixed btrfs save directory support, we grafted compression support too. If the kernel parameter "btrfscompress" is specified, the compression support for btrfs will be enabled, using the algorithm specified on that parameter. This has been tested to work wonderfully and using zstd, the compression rate is about 30% on average.

5. We have an update on the in-house "screencaster" application (a program record the video of the display). It now has the ability to take repeated screen capture, better quality video, among other things.

6. Step, another member of Fatdog team, has also revamped the "Samba Shares" application. It has been re-factored and is heavily tested to work across different Samba servers (different Windows versions, etc).

7. We have also fixed a long-standing bug when running Fatdog with RAM layer operation, which can cause inconsistencies if the system is heavily used (a lot of filesystem access) when the "merge down" process happens. SFR found this to be irritating enough to find a solution that works better; and this got incorporated into Fatdog.

An additional feature was also added: the ability to remove whiteouts if they don't hide any files on the lower SFS layers, but not activated by default due to possible conflict with multisession operation (we haven't tested the interaction yet).

8. We also include the "updater script" which re-enable VLC's ability to play youtube video directly, without having to update VLC itself. The script is called SFR found this script.

And of course, many other smaller bugfixes and feature addition, as well as adding and updating packages on the repo as well.

So when will we have a new release? Well, it will be released when it is released.

Posted on 19 Apr 2020, 16:17 - Categories: Fatdog64 Linux
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Fatdog64 810 Final is released

Maintenance release, basically a bug-fixed version of 810 Beta.

Release Notes and Forum announcements

Can't believe that Fatdog is coming to its twelfth year.

Download locations:, aarnet,,

Posted on 23 Jan 2020, 21:53 - Categories: Linux Fatdog64
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Fatdog64 810 Beta is Released

Maintenance release.

Release Notes and Forum announcements

Download locations:, aarnet,,

Posted on 9 Dec 2019, 02:37 - Categories: Fatdog64
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Fatdog64 801 is Released

It is a rolled-up updates, containing bugfixes and minor feature updates.

Release Notes and Forum announcements

Get it from the usual locations:
Primary site - (US) - European mirror - Australian mirror - European mirror

ISO Builder: Get it from here: and choose the builder dated 2019.05 and the package list for 801.


Posted on 4 May 2019, 22:20 - Categories: Fatdog64 Linux
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