Start you maker project and learn how to 3D with Blender (it’s marvelous 3D application). After Blender there is no excuse and it’s free (but remember if you really like it give something back). Are you on more on CAD? Learn 3D CAD with FreeCAD (Again amazing tool). Want to ride IoT wave but you don’t have too much money then get new shiny Tiny $5 Raspberry Pi Zero or 9$ C.H.I.P and make your Fritzing electric boogie with ease (and by the way you can commit those boards to library. It’s open source!). You are in music how about doing some DJ:n with linux? Mixxx just got shiny 2.0 RC1 out. Are you more reading type and need something to manage you e-books: Calibre is here to help. Huh so much to do so less time!

Where to get them? openSUSE have RPM for all of them just learn to search them from Packman or from OBS. Sorry to say Raspberry Pi Zero is currently not supported but you can help to add it to ARM boards working with openSUSE same problems with C.H.I.P (If you have Raspberry Pi 1/2 just get image for them from openSUSE ARM image and start hacking). You should learn how to add new repos to YaST2 and add Packman repo for new FreeCAD, Fritzing and Mixxx. Yes! most of them run also on Windows and Mac OS X. Now smile on, thumbs up and get your groove on with title song: De La Soul – Ring Ring Ring (Ha Ha Hey)

My first app

I been coding long time maybe too long. First I was using Pascal but it was too high level for me and not cool at all. When I started using Linux KDE 1 was Koolest desktop environment on earth and CDE was de-facto environment on for the big boys. Soon after KDE 2 was released I started using KDE PIM suite because KMail is still neat application and Korganizer was way better than Evolution. I realized I like to format my happenings in list which wasn’t supported the way I liked. I thought, ‘Hey what If I write console application for that. I know how to code C and Java so C++ can’t that hard?’.

It was possible. QT2 was really great GUI library for writing applications. That time QT licensing was insane but today it’s much easier to understand. Writing applications with KDE libraries wasn’t all that hard. Application was all main-function and soon as I got it working I mailed to KDE mailing list. I don’t have that mail any more and can’t find it from the net but it was something like: ‘Hello, I’m the best QT-coder ever and I have this app called KonsoleKalendar‘. I got very friendly feedback and it got included into CVS. I though now I’m greatest coder ever lived!

Actually I maintained KonsoleKalendar only short time and as I said I wasn’t happy about licensing of QT2 (It didn’t help that it was badly written application like ever). Most wonderful and bizarre thing is that KonsoleKalendar this exists in KDE5 and it’s in much better shape than when I left it. Afterwards this was the main learning point about collaboration in Open Source project for me. In start of 2000 there weren’t Git nor there where any fancy GUIs for sending patches. People mailed each other and tried to cope with CVS/Subversion and KDE still is very friendly community if you compare it to many others.

Getting along the communities

If you ever are going to cope the Open Source world try to get along with community. There is as many communities as there is project and they can be friendly, neutral, unknown or hostile. There are several nearly or really hostile projects where bug reports and patches are rejected with making fun of you body organs or mom. Hostile projects seems to have same pattern. There one master of universe mega alpha coder that dictators everything and then people who needs that project or are somehow contributed something that coder number one things that they can exists. If you cross this kind of project you should have very nice shielding or some precious code gems to take as bounty. Remember many very successful project also have that mega dictator which have some urge to make things happen. problem is that most of these dictators only understand code and can’t speak anything else.

Unknown projects are strangest ones. Common thing is that plenty of people use them and commit actively bug reports. Only few people commit changes to version control but they don’t pay any attention to bug reports or mailing-lists. libSDL is this kind of project. People share their patches on bug database but it’s nearly impossible to get them to code base or I just don’t understand how SDL development goes.

Neutral communities are nice. They have good management and clean orders how to contribute. You can get you patch or bug report in if it’s good enough. Neutral communities are somehow uneasy to enter but if you prove to make good contribution they let you make your thing. So what is difference with neutral and friendly. In friendly community you can ask stupid questions and someone answers you nicely not just blank silence or some kind RTFM answers.

How to contribute?

I tried to open situation little bit above but I give you example from Mixxx community which I’m most active these days. Most of people pop in mailing list and they have the best idea ever but they haven’t looked Mixxx code so they don’t know if it’s possible or not. If their ideas are reasonable and that human being is ready to do work it’s mostly greeted with some advises and notes how it should be made. After hiatus that developer commits Pull Request or not.

If Pull request been made then rough ride starts. Reviewing code is not a bad thing and people who are making these code reviews in Mixxx knows application well and only wants best code in.  For green contributor it can be very frustrating. Basicly you have to have good code quality to get into Mixxx code base and you have to sign contributor paper.

How fast this happens? It really depends size of you contribution and how badly it’s done. People are doing code review in their spare time so it can be slow. If you just get out of blue with Pull request in Github you most probably won’t get nothing in. In Mixxx everything gets in with Pull Request (if it’s trivial then it’s just LGTM and merge style stuff).

If you didn’t read anything else this is what I wanted to say

What I have learned are in these three things: Know community you are going to work with (it takes time and motivation), Know how to contribute (what are rules) and try to cope with some level of frustration (They can be very hard on you if you ask stupid questions because most of them are stupid in Open Source world). If you just stop development because project things your code is pile of sh*t and you have to work on it more. Understand it’s pile of sh*t until they are happy and you have to make it to their standard.  Every community it is always Dystopia of commiters. They decide what goes in and what doesn’t. If it’s your project you can choose but if you are not in enough you just have to cope with it. You can Fork code and start new project but believe most time it’s more progressive to stay in same project and try to change that. If it’s not possible then just Fork it but you can end up like FFmpeg and AVConv situation.

Working in Open Source project is about communication. So talk in mailing list, work on bug reports, write documentation and review code. If you are silent then you don’t exist and remember if you can’t code but you like to something there is always plenty to do. If you like to contribute learn: Git (Gitbub), Mercurial (Bitbucket), Subversion, Bug reporting (Mantis, Bugzilla), code structure of project and debugging/reading others code or if you are sysadmin, web designer or something else there always something to do. Remember if you think you are correct and everyone else if incorrect you are the one who have to prove them incorrect. Flaming and trolling is nice and fun but not going to get project forward.

I end here and remember these are my own notes.

What is license for?

Wear your tin-hats and make securing spells because here we go. In modern world everything is for sale and everything you can image will be stolen and in-incorporated in nuclear bomb or used in mass destruction of human beings. This ain’t new feature in human society. For example fire have been probably one man thing for long time (and I can just imagine how many jokes you can make about that poor fellow and that even poorer soul that first roasted something) after a while it widespread all over the world and same goes with wheel. They were invented somewhere and someone took them in use without giving a dime to the inventor. Is it fair? No it’s not. Bit harsh and unfair to this original guy but again this is how ball is played.

What this is related to licensing and what is the big deal of open source and free software anyway if this the Status Quo? What are the licenses for? Believe or not they are important agreements! It’s not secret that most of the Github repositories are still without proper license. That is why they launch: http://choosealicense.com/. Take time and study a bit or if you don’t have a time I’ll tell how I see things.

Free software

There is Free Software movement which is constructed around GNU project and FSF (Free Software Foundation). Most significant person in Free software is Richard Stallman (Yes that hansom guy with a beard) . If you want more history please read it from FSF site they know it more better than me. Main principals in Free software are Freedom, Freedom to share and make sure that everyone else have that freedom also.

Free Software licenses are commonly known as Copyleft licenses and most know is Gnu Public license (Actually version 3.0 ain’t that popular). All these licenses share a same thing. You will always have 4 freedoms:

• Freedom 0 – the freedom to use the work
• Freedom 1 – the freedom to study the work
• Freedom 2 – the freedom to copy and share the work with others
• Freedom 3 – the freedom to modify the work, and the freedom to distribute modified and therefore derivative works.

What this means (and I’m not a lawyer so don’t blame me if you get sued) is that you can make your changes to code, used it in nuclear bomb but if you release your bomb to big public (or make it available only in machine readable form) you must release also the code changes you have made to original code. There is eternal fight do these changes have to be delivered to upstream project and do they have to be suitable to attach into original code base.

This why every distribution is releasing their source packages (which ain’t bad thing at all) because GPL demands it. Copyleft tries to make sure you will get source code of binary if you demand it but it can be made available only for those who demand it and even in printed out form as A4 papers.

Copyleft there different opinions how these license articles really apply and there is plenty of violations like Allwinner. Still most of them a settled out of the court. One of the biggest GPL (which wasn’t about GPL license at all) that get in the court was (or is it still?) Linux kernel vs SCO. It was only possible because code was freely available and everyone could study it.

Because you didn’t read the anything above. Remember one thing Copyleft is VERY restrictive license. If you are using some library which is using Copyleft license of any form and you doing in-house development make sure you apply license demands before releasing your work or it could get real nasty. Main thing is: you have the right to use the source but same time you have to provide everyone else the same rights and no this doesn’t mean you have to have version control or bug tracker.

Puppy projects: Linux, Libreoffice, Blender and GIMP

Open source

Open Source licenses are widespread and there is plenty more of them than there is Copyleft licenses. How they compare Copyleft? Open Soure licenses tend to give you all rights so they are more liberal. Most popular licenses are MIT, Apache License 2.0 and BSD license. Why they are popular? It’s because they are simple and all these three gives you right to do what ever you want with these files and choose you want to contribute back. If you choose some not popular license you have to make sure you are compatible with GPL without that there is no game.

Why even have license then if you don’t care what people do with your stuff? Choosing liberate Open Source license is not letting everyone ‘steal’ your work it’s about making sure that they know what they can do with it and you are the owner of the rights. Project without any license or release as Public domain is most dangerous ever because you don’t know is this some kind of bomb project that author is waiting to spread and then he or she is making demand on court with statement ‘hey I have this code on Internet and this my new EULA! GIVE ME YOU €€€ (or $$$ sometimes £££) YOU FEALTY ROBBERS!’. These licenses most cases tell what kind of warranty you have and every time it’s next to nothing.

Why then choose Open Source license and not the Free Software? It’s about the attitude: Freedom makes freedom happen. With Free Software you are forced to be free and with Open Source you can choose what is your freedom level and of course you need something to fight about.

Puppy projects: Docker, FreeBSD, Apache HTTP server

What about something else that is not code

Back in days creative works was a weak spot of licensing. Free Software and Open Source license are very fitting to code but they are not very well fitting to creative work. This is why Creative Commons (commonly known as CC) was created. There is suitable licenses for sharing you images, writings or what ever. They have Copyleft style licenses and then more liberal ones. Take you time and find what fits to your project.

Lengthy post but nothing much to said

I think I’ll rest my case here. Next time I think I’ll post about contributing code and remember these are my OWN observations. If they are incorrect please let me know or if you hate me because I like Systemd and liberal licenses you can tell that too. Remember it’s your project and you can choose any license in the world you like.

Internet early days

As that Big company released Window 98 and after that Windows XP URW started to look akward as it was still a DOS (it included graphics but still). Distribution model changed from BBS to Internet WWW-page were you could download installation package (still Shareware) and pay for full version by mail.

In this point distributional things started to rise. People wanted to buy a game with credit card and that wasn’t popular way in Finland which caused little bit hustle. Answer for that was start using ‘Albert’s Ambry’ net distribution system. It was working as expected and it had all needed facilities only problem was Albert’s Ambry got out of business rather soon after URW entered to it.

Times goes by and Internet grows

After Albert’s Ambry get out of business years has passed and UnReal World RPG was distributed through it’s web-page. Everything worked just fine until download rate began to be so huge that Internet service provider started to complain about the traffic that URW caused monthly. Time for mirrors and bigger pipes. Paypal arrived and it made credit card payment things simpler.

Distribution models changes 2013 and UnReal World turned away from old-school Shareware system. Shareware is very good model but it’s rather heavy to use. You provide two versions of your application (one that is for testing and another with full whistles and bells or one that can be modelled to full version with password). Shareware was changed to donation based system (and if you want to donate to URW please do so. All money goes to development of the game [Except that food what two cats can eat]). Donation model is easier games like UnReal World which are regularly updated. You get full game straight a head and you donate if you like it.

Modern web days

In same year 2013 URW changed from Shareware to donation based it also was ported to Mac OS X and Linux (openSUSE, Fedora and Ubuntu/Debian supported currently every build). Port was done by me and it was rumble as you try get DOS game to another platform but it was also ported few years back to SDL1 so it wasn’t that bad.

I assume all you gamers know there is one mammoth in modern PC game distribution: Steam. There were also smaller players like: Desura. Their idea is the same. You have distribution system that is standardized (which all games should be working) and you can buy new games to your own catalogue with credit card from their system. URW entered to Desura last year and now Desura is out-of-business. Desura was great channel delivering applications (supported Linux, Mac OS X and Windows) but I understand it’s very difficult to make money when you are wrestling against Steam.

In near future UnReal World RPG will in Steam as it get through Green light program. Hopefully it doesn’t give death kiss to that service too.

Lessons learned

Take time to make your installers as good as you can get. There is no excuse to have awful installer or Tar/RPM/DEB/DMG-package. If anyone can’t play your game straight away they will complain to you or they just move away without taking any second though. That is the power of Steam.

Don’t trust just one distribution model. If your distributor goes out of business have plan B on hand (very near if possible). If you are doing games for Apple iOS then you are out of luck but If you can use multiple ways to distribute your software do it. You need to work little bit more but more places more eyes to stare your application but. Remember these days many youngsters just play what they can download from Steam (and not blaming them from that) or some other shop that is tied to their device. They don’t know how to install game from Internet or they just don’t care.

If you support Linux (as you should). Ubuntu is biggest but also Arch people are fast growing player community (Fedora is non exist and openSUSE is mediocre). Have at least Ubuntu and provide DEB-package (in future Snappy) and if possible TAR-package (If you are willing provide RPM and Arch package). Have menu integration and do you homework with Linux. In future Linux gaming will be on rise if Steam machines take any market share and today you can buy many Linux AAA-games (over 1000) from Steam today!

Sorry to write this but truth is: In many cases user are all wrong (they just can’t understand how to play your game) but they pay the bills so make yourself a favour: fix bugs fast and give support at least at some forum. Community around the game is very hard to build and it even easier to lose. Final wisdom: last support multi platform. Mac OS X and Linux downloads are minority but do you want to cut these customers out?

Ok summer is crazy.. endless and crazy.. Peace out!

After doing little bit homework I popped up with XWax which is an open-source Digital Vinyl System (DVS) for Linux. It works great and believe me it’s geeky. Still it left me little bit blank because I liked to use some Dj controller to load music.  XWax doesn’t support Dj controller at least I didn’t get mine working. So back to square one.

Then I crossed Mixxx and it looked very promising but Mixxx version 1.10 left much to hope for. After a short while they released version 1.11 which was better but I noted that plenty of MP4 format audio files didn’t work (most of the my music is encoded with Vorbis and wrapped with Ogg that works great but if you buy something they tend to favour MP4).

Make long story short. I get involved with Mixxx and it have very nice community, fixed non-working FFmpeg plug in and fixed handfull of Linux specific stuff. After making FFmpeg plug in working I noticed I have solved most of my digital Dj problems. Mixxx works with Linux… check, openSUSE.. thank you for asking yes, is open source… GPLv2, Dj controllers.. long list,  Digital vinyls.. serato and traktor and have nice working skinnable interface.. check.

Only thing is that Mixxx is using Portaudio with Linux and Portaudio doesn’t play nice with Pulseaudio but I wrote patch for Portaudio and it’s currently in ‘works for me’-stage which means late Beta. If I ever got time I’ll give it a facelift, commit it to Github and generate little bit documentation and try to again get it to official Portaudio

But if you are open source Dj and like to test state-of-art version (which is light years ahead last one) of Mixxx I’ll recommend to test Mixxx version 1.12 beta. You should understand it’s Beta software and if you find bug please report it. But if you want to stick with stable Mixxx version 1.11 there is nothing wrong with that it’s also very capable application.

In openSUSE you can download it with zypper from Packman repos.

It seems that there is some problems with  OpenGL/DirectX and other accelerations APIs that they don’t play together without tweaking and researching ways to make them work. Okay this ain’t SDL2 fault completely this manufacturer problem again but.. you use SDL2 to get rid of hardware problems.

All those problems are solvable with current SDL2 version but again they takes lots of time and someone who is willing to debug application in non-working machine and remember this is normal stuff in development and not a big thing. But it’s big thing when you are about to releasing your new bling bling game with megalomanic blitting and your surfaces starts to blink every time you blit with some random machines. Even in not so bling bling UnReal Wolrd RPG you have problem with that but they are solved now but I builded many many Mac OS X and Linux builds before problem was traced to SDL2 related. If you are Apple people I point my finger to you. What the heck you are doing to openGL in Mac OS X??

SDL2 is what open source library but their biggest problems (in my opinion) are these: Hey Wiki is nice but have proper Doxygen or something documentation (which should be official), You have Bugzilla but there is no connection (or I just didn’t noticed) how bugs and Mercurial repository communicate each other and where/how you communicate with you users (mailinglists are so 90′ how about posting some news)?

What this leads is people post patches to Bugzilla where they get to nowhere and other one are using them because they solve their problem. This leads in situation where there is unofficial SDL2 libraries that are not compatible with each other. This is normal situation in open source world and SDL2 is under ZLib license so you can do it but what happens when they fix something that was broken to official SDL2 library and you using older one in development that is patched to work?

This is not SDL2 specific thing it’s very common situation with many open source projects (and yes they tend to have limited man power if you like to fix them you can! Learn to communicate with those people like I should with SDL2 people) but in a way SDL2 have deep connection with Valve (They use it in Linux steam client at least) and Steam ain’t small company they should but power behind this or let it go.

At the end remember this ain’t rant against SDL2 or SDL2 developers. They are doing hard work for you getting mostly nothing out of it. Because Eastern is all about pain and unhappiness so this was my contribution to that or no not really people!! Life is too short for sadness so have a lot’s of fun all eastern!

History

LibAO is developed under Xiph umbrella. Xiph is the organization who brought you Ogg/Vorbis, FLAC, Theora and currently they are hammering together next generation video codec Daala. Opus-audio codec standard is also Xiph project. LibAO rised from Xiph’s need multi-platform audio output library for Vorbis-audio codec. In this point if you don’t have any glue what I just said in last sentences I think you should take your spoon and start shovelling about Open Source audio codecs.
Becaus of the history libAO only has output mode and doesn’t use any callbacks. It doesn’t have fancy Float32 mode (as much as I understood) but that doesn’t say it’s bad thing. It works as expected you just feed bytes and after while you hear them from your speakers.

What about API

Supported outputs: Alsa, Oss, Jack, Mac OS X, Windows
License: GNU General Public license 2.0+

As said libAO API is difficult to describe since there almost ain’t NAN of it. You initialize, ask output device, put in your mode settings and start feeding data. Pulseaudio simple is almost easy as this but it’s still more difficult if you compare it to libAO. LibAO doesn’t support recording so only output and there must be a way to use another device than default but it’s not very easy to find or I was too lazy to dig it out.

So who wants to use libAO? People in hurry and don’t mind GPL-license, someone with very very tiny need of just getting audio out and people how hate bloat.

Summary: So if you hate bloat and again license doesn’t make you unhappy please use this library. Still libAO has kind of same problem that ALSA has. It’s mature, usable and ready for hardcore torturing but is it sexy? No! Is fresh? No, No! Is something that will change it API every week or hour?

After this I have to choose what to bring next. I have FFmpeg, Gstreamer and VLC in row. If you have opinion about next framework let me know.

Loki only shipped CD’s for installing your application and there wasn’t hot fixes waiting when you got CD from post or yes there where but I had to wait and wait for 200 MB blob to download for ages with my 57600 modem. All the time I thought that I’ll boot Windows for playing Castle Wolfestein. It was long before before Linux have any gaming community what so ever. There weren’t Firefox or Chrome available and Google was just starting to own our lifes.  So it was dark days of late ’90 (we had electricity thanks for asking).

Loki was founded on 1998 and  it got on bankruptcy on 2001 after IT bubble blowed. Loki changed Linux in good way. One thing that they left behind was called Simple Direct Layer (SDL1). SDL layer sits top on Xorg that makes creating games more ease. You can port your game to Windows and Mac OS X with little effort. Current version of SDL is SDL2.

Good thing about SDL is that it abstracts drawing to screen in Windows, Mac OS X and X-windows. SDL1 was all about pixel buffers but SDL2 is all about surfaces and acceleration. It support many more OSes but that’s not the what we are looking at today. So how do you playing audio out of SDL1/2?. Good thing is audio interface stayed same through conversion from SDL1 to SDL2. They only added few bugs and float point audio in SDL2.  SDL1 have recording but I didn’t manage to make it work so if anyone with more patience than me can lead me to correct path I would be happy puppy. Here is SDL Github location: https://github.com/illuusio/linux-audio-example/tree/master/sdl

Simple Direct Layer API

Supported outputs: Alsa, Oss, Pulseaudio, Mac OS X, Windows, iOS, Android
License: SDL1 GNU Lesser General Public License 2.1 and SDL2 ZLib license

SDL API is like name says very simple and it’s very popular toolkit. SDL can be found on every bigger Linux distribution out of box (at least SDL1 and SDL2 is fast spreading). SDL can be used for graphics, input and audio. SDL API is actually almost dead simple. Support for audio outputs if very good on Linux and things are like if it’s working on Linux it works on Mac OS X and Windows the same.  Playing audio was so easy that I get frustrated when I tried to make recording example. I even read the source code how it should be done and yes It doesn’t work with SDL2 that what I learner but I couldn’t get it working in SDL1 nether.
SDL audio API is fully and only callback based. You give your callback function and it just get called when SDL feels audio should be played. After that you feed the correct type output as much callback asks and then you wait another callback to feed more. Simple and very efficient.
If you compare callback system to Pulseaudio with SDL you can’t get no information what ALSA, Pulseaudio or OSS is doing. You just feed and they just get played out of speakers. If audio is that what makes your game rock then SDL could be what you want.

SDL audio for whom.

It’s for people who don’t need much or don’t have interested how audio get played. People who likes to get audio out with ease and fast. Currently SDL development is under Steam umbrella so they have some commercial interest with it. SDL1 was licensed with LGPL+2.0 and SDL2 is under Zlib license which mostly same like than MIT-license. SDL is also mostly rock solid, sanely licensed (SDL2) and used by many many Indie (The UnReal World RPG if I have to mention one Indie game that I know well) and not so Indie games. Biggest problem with whole SDL is lack of documentation. There is wiki but if there is no question you crawler through web and test everything you find along if it solves your problem. Development is also little bit slow and fixing bugs are not getting fixed in fast but if you can live with that it’s all yours!

Summary: Very simple to get audio out of speaker. Not for high-end or surround sound but mostly for games or playing videos this is excellent! Learning curve is non exist or  there is small: you got to understand C well to work with SDL. Works with IOS and Android so if you are on cross platform this can help you out.

Open Sound System

First let’s talk about Open Sound System first before going to ALSA. After that we talk about todays topic: Pulseaudio.  I recall correct OSS was the first sound system that provided support for audio in Linux kernel. Even today it’s emulated by ALSA and you can use it as output with Pulseaudio. Real OSS still lives as Proprietary library and it’s implemented in several OS like FreeBSD.
If you look OSS as API point of view it’s very blocking because it uses heavily IOCTL-calls and because they are direct memory calls you have to wait. Only reason I can imagine why someone wants to support OSS in new application is trying to support whole UNIX family. If it’s not must then trust me you don’t want OSS. Event lack of duplex audio wasn’t biggest problem at late ’90.  I had Gravis Ultrasound and OSS support sucked a lot. ALSA wasn’t even pre-alpha and without thinking I jumped that rapidly moving wagon.

ALSA

Advanced Linux Sound Architecture is current Linux Audio API. You should use it for new applications and it has impressive set of supported audio chips. I haven’t find a single audio hardware that doesn’t work. Only problem with ALSA is that is so stable that it’s getting little bit too mature. times have change from ’90 and ALSA is starting look not fantastic like I thought about it first but just OK.
Getting your hardware working is not the complicated case with ALSA. Hard part comes whne you want set up more complicated patterns like USB audio, Bluetooth or send audio to another machine for playing.

Nowadays Every other platforms than Linux desktop had neat audio servers. There have been several attempts for Linux also ESD, KDE audio server and several others that never reached much attention. There is also JACK but it’s again little bit too hard to use and not for old morons like me. Believe I have use it for high-end stuff and I cannot recommend it more but when you just want your audio come from the speaker without routing it half an hour then Pulseaudio is just better, sorry you can hate me being old senile fart.

Pulseaudio

Supported outputs: Alsa, Oss, Jack, Mac OS X, Windows
License: GNU Lesser General Public License 2.1

So why we talked ALSA and OSS? Because Pulseaudio doesn’t handle sound cards. It expects that someone else have knowledge about what cards are in system and how to use them. Pulseaudio just provides common way to use them. But let’s start from beginning shall we? Lennart Poettering is who created Pulseaudio. His new beast Systemd is just like Pulseaudio hated from the start and dividing Linux community but making huge impact in Linux. Pulseaudio was meant to be replacement for Gnome ESD and there is compatibility layer for ESD available.  Pulseaudio works for  KDE, XFCE and others. Prove me wrong but I don’t know anyone how misses ESD! I miss KDE 2.0 Audio server Arts in sentimental moments but in my point of view ESD was horrible piece of crap. My opinion is only Android Audioflinger is more popular audio server in Linux world. Sometimes I wonder why Pulseaudio doesn’t provide Audioflinger compatibility layer? How does Pulseaudio sit top of the Linux audio stack. I try to make nice picture of it.

If you want to talk to sound card you make connection to Pulseaudio server with Pulseaudio C-library and talk to the Pulseaudio. Not direct to ALSA not direct to sound card. Pulseaudio is built upon sockets so you can access Pulseaudio from another machine or from network if you have bandwidth and play your tunes from or to other machine. Pulseaudio takes care about find out what sound cards you may have and connecting to them for example Bluetooth audio device. What is so wrong with Pulseaudio if it’s working so well? Basicly, it adds latency between application and audio coming out of speakers. Not me or not you not your mother are going to spot it but those nerdy super HIFI audio humans (Homo HIFIcus) can spot it. If you have some very bad audio chip there you notice but 99% times you are happier with Pulseaudio than without it.

Stop praising Pulseaudio and get to API

As beautiful as Pulseaudio API is it’s horrible same time! Modern slick callback based monster that just does something and at the you get audio or you can play it so feed me with bytes. I think they noticed this and made blocking Simple API. Which is very simple and easy to use. If you don’t want to use Pulseaudio Simple API then oh boy!
There is two main mode which you can use if we count Simple API out. There is normal mainloop and threaded mainloop. So if you want to control everything you choose mainloop mode. You iterate your mainloop and get events to your callbacks or you can let Pulseaudio do it with pa_mainloop_run() command. In threaded version it just runs and gives you callback as you go. Difference is that threaded loop stays away of you sight and normal blocks your application.

What kind of callbacks there is?

In Pulseaudio question is more like what doesn’t have callback. Stream is ready, check, buffer underrrun, check, something weird just happen, check. You just choose what to implement and then they appear as they happen. Then you choose do something or not.

Is there something wrong with this. No there isn’t, it works as expected. Actually it worked better than I was expecting. Learning curve for Pulseaudio is bit high because fully understanding how Pulseaudio works takes time and patience.

Summary:  Little bit weird pure C API but when correctly implemented very powerful. Widely spread in Linux world such all major distributions use it. Even it support Mac OS X and Windows it’s not really as easily portable at it sounds. It’s little bit Linux specific although BSD family is  beginning to use it. But if you need to support Linux and want to have higher level API than ALSA then this is for you but most frameworks support it so you can also leave it to them and not shovel into API.

Application

Like I said example applications are very simple. With Every library I tried to write playback and record example. If you can use blocking API interface there is blocking example also. In these Examples I use sndfile because API is super easy to use and I could test with WAV. So no troubles big bobbles approach.

Code

I won’t be posting code here it can be found on Github repository. I tried to be super clear as they are examples and added comments as needed but if you don’t get glue fault is all mine.

Portaudio

Supported outputs: Alsa, Oss, Jack, Mac OS X CoreAudio and Many Windows Audio API’s

Why do want to use something else than ALSA? If you need to support other platforms than Linux you get idea of cross platform API for audio. Portaudio is hidden gem of Linux audio libraries. It’s stable as can get. Portaudio has blocking and callback support. It has Float 32-bit Int 32-, 16- and 8-bit input/output. I tries to be very high end in every corner. Also licensing is very liberal.  For a while It’s has seen slowing development  because main developers have something else to do in life.

For me biggest no-no for me was lack of Pulseaudio support (I go so upset that I wrote Pulseaudio  hostApi for Portaudio but that is worth of another blog post). Portaudio supports Windows, Linux and Mac OS X so it’s good choice if you need same quality audio in every platform.

Biggest minus in Portaudio is there ain’t much applications using it. There is some highlights like Mixxx and Audacity. Rest of the list can be found here. Why it’s not more popular I can’t say because it’s easy to use.

Summary: Simple but powerful API for I/O which I can recommend. So go and see examples if it’s for you and documentation from official pages. Next time we get on Pulseaudio.