PulseAudio

Horay! I participate in this year’s Google Summer of Code and I’ll be involvled in PulseAudio community to help enhance the logging and testing facilities. Let me first introduce what’s GSoC (Google Summer of Code), it’s a project hosted by Google ... [More] every year to motivate students to be engaged in open source projects. Students will have a meaningful summer and be paid for their hard coding work. Then PulseAudio project. If you’re using a modern Linux desktop, then chances are that you’re already using this software. It’s the component which helps to mix all the sounds from other applications and then output them into your speakers or headphones. Finally me I’m a student from East China Normal University. Technically speaking, I’m not majoring in computer science, nor anything related to it. But I’m inspired by my friends and now I’m happy to say that I could CODE! This is the coolest skill, that is, I can make almost anything into reality. I’m so lucky to be chosen into PulseAudio community. I’d love to thanks all the developers in this community. My mentor Arun, and the maintainer Colin, and Tanu even had a full code review on my proof of concept of circular log buffering patch! Well, let me share some tips how you would be better selected in GSoC. First, start early! Early birds catches the worms. Each year’s schedule is quite similar, find out last year’s accepted projects and see which one interests you most. This whole list is quite long, so start early to find out your interests! Second, be involved in the community. Once you’ve found one project, the first thing you should do is to be invovled in the community. Being involved has different meanings, the first step is of course to download the software and have a try, be a user! And then be a tester. Then, you can find out from its website to see how to setup your developement environment. Sign up for the mailing list, or even hang out in its IRC channel. Third, do your homework. Now it comes the hard part. After some tests and uses, you may wonder, “hey, this could be enhanced!” or “I would this feature in another way!”. That’s a good sign, this means you have your own opinion on what the project should be shaped. Then start small and write a simple demo to show you are ABLE to do this project. In my application, I spent about one week to write the circular log buffer demo and it turns out to be useful of getting myself faimilar with its internals. Now here are some words about this blog. According to the advice from Colin, I’m setting this blog up to mainly track my status of this summer project. However, possibly this blog would have more technically contents later on with more engagement in open source community. It’s a good start, isn’t it? [Less]

That’s right, it’s finally out! Thanks go out to all our contributors for the great work (there’s too many — see the shortlog!). The highlights of the release follow. Head over to the announcement or release notes for more details. Dynamic sample ... [More] rate switching by Pierre-Louis Bossart: This makes PulseAudio even more power efficient. Jack detection by David Henningsson: Separate volumes for your laptop speakers and headphones, and more stuff coming soon. Major echo canceller improvements by me: Based on the WebRTC.org audio processing library, we now do better echo cancellation, remove the need to fiddle with the mic volume knob and have fixed AEC between laptop speakers and a USB webcam mic. A virtual surround module by Niels Ole Salscheider: Try it out for some virtual surround sound shininess! Support for Xen guests by Giorgos Boutsiouki: Should make audio virtualisation in guests more efficient. Special thanks from me to Collabora for giving me some time for upstream work. Packages are available on Gentoo, Arch, and probably soon on other distributions if they’re not already there. [Less]

That’s right, it’s finally out! Thanks go out to all our contributors for the great work (there’s too many — see the shortlog!). The highlights of the release follow. Head over to the announcement or release notes for more details. Dynamic sample ... [More] rate switching by Pierre-Louis Bossart: This makes PulseAudio even more power efficient. Jack detection by David Henningsson: Separate volumes for your laptop speakers and headphones, and more stuff coming soon. Major echo canceller improvements by me: Based on the WebRTC.org audio processing library, we now do better echo cancellation, remove the need to fiddle with the mic volume knob and have fixed AEC between laptop speakers and a USB webcam mic. A virtual surround module by Niels Ole Salscheider: Try it out for some virtual surround sound shininess! Support for Xen guests by Giorgos Boutsiouki: Should make audio virtualisation in guests more efficient. Special thanks from me to Collabora for giving me some time for upstream work. Packages are available on Gentoo, Arch, and probably soon on other distributions if they’re not already there. [Less]

pulseaudio: PulseAudio 2.0 is out! Our tweets sound even better now! http://t.co/S5DwpkIS (by Arun)

There's one feature In the upcoming Fedora 17 release that is immensly useful but very little known, since its feature page 'ckremoval' does not explicitly refer to it in its name: true automatic multi-seat support for Linux. A multi-seat computer ... [More] is a system that offers not only one local seat for a user, but multiple, at the same time. A seat refers to a combination of a screen, a set of input devices (such as mice and keyboards), and maybe an audio card or webcam, as individual local workplace for a user. A multi-seat computer can drive an entire class room of seats with only a fraction of the cost in hardware, energy, administration and space: you only have one PC, which usually has way enough CPU power to drive 10 or more workplaces. (In fact, even a Netbook has fast enough to drive a couple of seats!) Automatic multi-seat refers to an entirely automatically managed seat setup: whenever a new seat is plugged in a new login screen immediately appears -- without any manual configuration --, and when the seat is unplugged all user sessions on it are removed without delay. In Fedora 17 we added this functionality to the low-level user and device tracking of systemd, replacing the previous ConsoleKit logic that lacked support for automatic multi-seat. With all the ground work done in systemd, udev and the other components of our plumbing layer the last remaining bits were surprisingly easy to add. Currently, the automatic multi-seat logic works best with the USB multi-seat hardware from Plugable you can buy cheaply on Amazon (US). These devices require exactly zero configuration with the new scheme implemented in Fedora 17: just plug them in at any time, login screens pop up on them, and you have your additional seats. Alternatively you can also assemble your seat manually with a few easy loginctl attach commands, from any kind of hardware you might have lying around. To get a full seat you need multiple graphics cards, keyboards and mice: one set for each seat. (Later on we'll probably have a graphical setup utility for additional seats, but that's not a pressing issue we believe, as the plug-n-play multi-seat support with the Plugable devices is so awesomely nice.) Plugable provided us for free with hardware for testing multi-seat. They are also involved with the upstream development of the USB DisplayLink driver for Linux. Due to their positive involvement with Linux we can only recommend to buy their hardware. They are good guys, and support Free Software the way all hardware vendors should! (And besides that, their hardware is also nicely put together. For example, in contrast to most similar vendors they actually assign proper vendor/product IDs to their USB hardware so that we can easily recognize their hardware when plugged in to set up automatic seats.) Currently, all this magic is only implemented in the GNOME stack with the biggest component getting updated being the GNOME Display Manager. On the Plugable USB hardware you get a full GNOME Shell session with all the usual graphical gimmicks, the same way as on any other hardware. (Yes, GNOME 3 works perfectly fine on simpler graphics cards such as these USB devices!) If you are hacking on a different desktop environment, or on a different display manager, please have a look at the multi-seat documentation we put together, and particularly at our short piece about writing display managers which are multi-seat capable. If you work on a major desktop environment or display manager and would like to implement multi-seat support for it, but lack the aforementioned Plugable hardware, we might be able to provide you with the hardware for free. Please contact us directly, and we might be able to send you a device. Note that we don't have unlimited devices available, hence we'll probably not be able to pass hardware to everybody who asks, and we will pass the hardware preferably to people who work on well-known software or otherwise have contributed good code to the community already. Anyway, if in doubt, ping us, and explain to us why you should get the hardware, and we'll consider you! (Oh, and this not only applies to display managers, if you hack on some other software where multi-seat awareness would be truly useful, then don't hesitate and ping us!) Phoronix has this story about this new multi-seat support which is quite interesting and full of pictures. Please have a look. Plugable started a Pledge drive to lower the price of the Plugable USB multi-seat terminals further. It's full of pictures (and a video showing all this in action!), and uses the code we now make available in Fedora 17 as base. Please consider pledging a few bucks. Recently David Zeuthen added multi-seat support to udisks as well. With this in place, a user logged in on a specific seat can only see the USB storage plugged into his individual seat, but does not see any USB storage plugged into any other local seat. With this in place we closed the last missing bit of multi-seat support in our desktop stack. With this code in Fedora 17 we cover the big use cases of multi-seat already: internet cafes, class rooms and similar installations can provide PC workplaces cheaply and easily without any manual configuration. Later on we want to build on this and make this useful for different uses too: for example, the ability to get a login screen as easily as plugging in a USB connector makes this not useful only for saving money in setups for many people, but also in embedded environments (consider monitoring/debugging screens made available via this hotplug logic) or servers (get trivially quick local access to your otherwise head-less server). To be truly useful in these areas we need one more thing though: the ability to run a simply getty (i.e. text login) on the seat, without necessarily involving a graphical UI. The well-known X successor Wayland already comes out of the box with multi-seat support based on this logic. Oh, and BTW, as Ubuntu appears to be "focussing" on "clarity" in the "cloud" now ;-), and chose Upstart instead of systemd, this feature won't be available in Ubuntu any time soon. That's (one detail of) the price Ubuntu has to pay for choosing to maintain it's own (largely legacy, such as ConsoleKit) plumbing stack. Multi-seat has a long history on Unix. Since the earliest days Unix systems could be accessed by multiple local terminals at the same time. Since then local terminal support (and hence multi-seat) gradually moved out of view in computing. The fewest machines these days have more than one seat, the concept of terminals survived almost exclusively in the context of PTYs (i.e. fully virtualized API objects, disconnected from any real hardware seat) and VCs (i.e. a single virtualized local seat), but almost not in any other way (well, server setups still use serial terminals for emergency remote access, but they almost never have more than one serial terminal). All what we do in systemd is based on the ideas originally brought forward in Unix; with systemd we now try to bring back a number of the good ideas of Unix that since the old times were lost on the roadside. For example, in true Unix style we already started to expose the concept of a service in the file system (in /sys/fs/cgroup/systemd/system/), something where on Linux the (often misunderstood) "everything is a file" mantra previously fell short. With automatic multi-seat support we bring back support for terminals, but updated with all the features of today's desktops: plug and play, zero configuration, full graphics, and not limited to input devices and screens, but extending to all kinds of devices, such as audio, webcams or USB memory sticks. Anyway, this is all for now; I'd like to thank everybody who was involved with making multi-seat work so nicely and natively on the Linux platform. You know who you are! Thanks a ton! [Less]

There's one feature In the upcoming Fedora 17 release that is immensly useful but very little known, since its feature page 'ckremoval' does not explicitly refer to it in its name: true automatic multi-seat support for Linux. A multi-seat computer ... [More] is a system that offers not only one local seat for a user, but multiple, at the same time. A seat refers to a combination of a screen, a set of input devices (such as mice and keyboards), and maybe an audio card or webcam, as individual local workplace for a user. A multi-seat computer can drive an entire class room of seats with only a fraction of the cost in hardware, energy, administration and space: you only have one PC, which usually has way enough CPU power to drive 10 or more workplaces. (In fact, even a Netbook has fast enough to drive a couple of seats!) Automatic multi-seat refers to an entirely automatically managed seat setup: whenever a new seat is plugged in a new login screen immediately appears -- without any manual configuration --, and when the seat is unplugged all user sessions on it are removed without delay. In Fedora 17 we added this functionality to the low-level user and device tracking of systemd, replacing the previous ConsoleKit logic that lacked support for automatic multi-seat. With all the ground work done in systemd, udev and the other components of our plumbing layer the last remaining bits were surprisingly easy to add. Currently, the automatic multi-seat logic works best with the USB multi-seat hardware from Plugable you can buy cheaply on Amazon (US). These devices require exactly zero configuration with the new scheme implemented in Fedora 17: just plug them in at any time, login screens pop up on them, and you have your additional seats. Alternatively you can also assemble your seat manually with a few easy loginctl attach commands, from any kind of hardware you might have lying around. To get a full seat you need multiple graphics cards, keyboards and mice: one set for each seat. (Later on we'll probably have a graphical setup utility for additional seats, but that's not a pressing issue we believe, as the plug-n-play multi-seat support with the Plugable devices is so awesomely nice.) Plugable provided us for free with hardware for testing multi-seat. They are also involved with the upstream development of the USB DisplayLink driver for Linux. Due to their positive involvement with Linux we can only recommend to buy their hardware. They are good guys, and support Free Software the way all hardware vendors should! (And besides that, their hardware is also nicely put together. For example, in contrast to most similar vendors they actually assign proper vendor/product IDs to their USB hardware so that we can easily recognize their hardware when plugged in to set up automatic seats.) Currently, all this magic is only implemented in the GNOME stack with the biggest component getting updated being the GNOME Display Manager. On the Plugable USB hardware you get a full GNOME Shell session with all the usual graphical gimmicks, the same way as on any other hardware. (Yes, GNOME 3 works perfectly fine on simpler graphics cards such as these USB devices!) If you are hacking on a different desktop environment, or on a different display manager, please have a look at the multi-seat documentation we put together, and particularly at our short piece about writing display managers which are multi-seat capable. If you work on a major desktop environment or display manager and would like to implement multi-seat support for it, but lack the aforementioned Plugable hardware, we might be able to provide you with the hardware for free. Please contact us directly, and we might be able to send you a device. Note that we don't have unlimited devices available, hence we'll probably not be able to pass hardware to everybody who asks, and we will pass the hardware preferably to people who work on well-known software or otherwise have contributed good code to the community already. Anyway, if in doubt, ping us, and explain to us why you should get the hardware, and we'll consider you! (Oh, and this not only applies to display managers, if you hack on some other software where multi-seat awareness would be truly useful, then don't hesitate and ping us!) Phoronix has this story about this new multi-seat support which is quite interesting and full of pictures. Please have a look. Plugable started a Pledge drive to lower the price of the Plugable USB multi-seat terminals further. It's full of pictures (and a video showing all this in action!), and uses the code we now make available in Fedora 17 as base. Please consider pledging a few bucks. Recently David Zeuthen added multi-seat support to udisks as well. With this in place, a user logged in on a specific seat can only see the USB storage plugged into his individual seat, but does not see any USB storage plugged into any other local seat. With this in place we closed the last missing bit of multi-seat support in our desktop stack. With this code in Fedora 17 we cover the big use cases of multi-seat already: internet cafes, class rooms and similar installations can provide PC workplaces cheaply and easily without any manual configuration. Later on we want to build on this and make this useful for different uses too: for example, the ability to get a login screen as easily as plugging in a USB connector makes this not useful only for saving money in setups for many people, but also in embedded environments (consider monitoring/debugging screens made available via this hotplug logic) or servers (get trivially quick local access to your otherwise head-less server). To be truly useful in these areas we need one more thing though: the ability to run a simply getty (i.e. text login) on the seat, without necessarily involving a graphical UI. The well-known X successor Wayland already comes out of the box with multi-seat support based on this logic. Oh, and BTW, as Ubuntu appears to be "focussing" on "clarity" in the "cloud" now ;-), and chose Upstart instead of systemd, this feature won't be available in Ubuntu any time soon. That's (one detail of) the price Ubuntu has to pay for choosing to maintain it's own (largely legacy, such as ConsoleKit) plumbing stack. Multi-seat has a long history on Unix. Since the earliest days Unix systems could be accessed by multiple local terminals at the same time. Since then local terminal support (and hence multi-seat) gradually moved out of view in computing. The fewest machines these days have more than one seat, the concept of terminals survived almost exclusively in the context of PTYs (i.e. fully virtualized API objects, disconnected from any real hardware seat) and VCs (i.e. a single virtualized local seat), but almost not in any other way (well, server setups still use serial terminals for emergency remote access, but they almost never have more than one serial terminal). All what we do in systemd is based on the ideas originally brought forward in Unix; with systemd we now try to bring back a number of the good ideas of Unix that since the old times were lost on the roadside. For example, in true Unix style we already started to expose the concept of a service in the file system (in /sys/fs/cgroup/systemd/system/), something where on Linux the (often misunderstood) "everything is a file" mantra previously fell short. With automatic multi-seat support we bring back support for terminals, but updated with all the features of today's desktops: plug and play, zero configuration, full graphics, and not limited to input devices and screens, but extending to all kinds of devices, such as audio, webcams or USB memory sticks. Anyway, this is all for now; I'd like to thank everybody who was involved with making multi-seat work so nicely and natively on the Linux platform. You know who you are! Thanks a ton! [Less]

Derek Foreman has finally written up a nice blog post about his Androgenizer tool, which we’ve used for porting PulseAudio, GStreamer, Wayland, Telepathy and most of their dependencies to Android. If you’ve got an autotools-based project that you’d like to build on Android, whether on the NDK or system-wide this is really useful.

Derek Foreman has finally written up a nice blog post about his Androgenizer tool, which we’ve used for porting PulseAudio, GStreamer, Wayland, Telepathy and most of their dependencies to Android. If you’ve got an autotools-based project that you’d like to build on Android, whether on the NDK or system-wide this is really useful.

Some of you might’ve noticed that there has been a bunch of work happening here at Collabora on making cool open source technologies such as GStreamer, Telepathy, Wayland and of course, PulseAudio available on Android. Since my last blog post on ... [More] this subject, I got some time to start looking at replacing AudioFlinger (recap: that’s Android’s native audio subsystem) with PulseAudio (recap: that’s the awesome Linux audio subsystem). This work can be broken up into 3 parts: playback, capture, and policy. The roles of playback and capture are obvious. For those who aren’t aware of system internals, the policy bits take care of audio routing, volumes, and other such things. For example, audio should play out of your headphones if they’re plugged in, off Bluetooth if you’ve got a headset paired, or the speakers if nothing’s plugged in. Also, depending on the device, the output volume might change based on the current output path. I started by looking at solving the playback problem first. I’ve got the first 80% of this done (as we all know, the second 80% takes at least as long ;) ). This is done by replacing the native AudioTrack playback API with a simple wrapper that translates into the libpulse PulseAudio client API. There’s bits of the API that seem to be rarely used(loops and markers, primarily), and I’ve not gotten around to those yet. Basic playback works quite well, and here’s a video showing this. (Note: this and the next video will be served with yummy HTML5 goodness if you enabled the YouTube HTML5 beta). (if the video doesn’t appear, you can watch it on YouTube) Users of PulseAudio might have spotted that this now frees us up to do some fairly nifty things. One such thing is getting remote playback for free. For a long time now, there has been support for streaming audio between devices running PulseAudio. I wrote up a quick app to show this working on the Galaxy Nexus as well. Again, seeing this working is a lot more impressive than me describing it here, so here’s another video: (if the video doesn’t appear, you can watch it on YouTube) This is all clearly work in progress, but you can find the code for the AudioTrack wrapper as a patch for now. This will be a properly integrated tree that you can just pull and easily integrate into your Android build when it’s done. The PA Output Switcher app code is also available in a git repository. I’m hoping to be able to continue hacking on the capture and policy bits. The latter, especially, promises to be involved, since there isn’t always a 1:1 mapping between AudioFlinger and PulseAudio concepts. Nothing insurmountable, though. :) Watch this space for more updates as I wade through the next bit. [Less]

Some of you might’ve noticed that there has been a bunch of work happening here at Collabora on making cool open source technologies such as GStreamer, Telepathy, Wayland and of course, PulseAudio available on Android. Since my last blog post on ... [More] this subject, I got some time to start looking at replacing AudioFlinger (recap: that’s Android’s native audio subsystem) with PulseAudio (recap: that’s the awesome Linux audio subsystem). This work can be broken up into 3 parts: playback, capture, and policy. The roles of playback and capture are obvious. For those who aren’t aware of system internals, the policy bits take care of audio routing, volumes, and other such things. For example, audio should play out of your headphones if they’re plugged in, off Bluetooth if you’ve got a headset paired, or the speakers if nothing’s plugged in. Also, depending on the device, the output volume might change based on the current output path. I started by looking at solving the playback problem first. I’ve got the first 80% of this done (as we all know, the second 80% takes at least as long ;) ). This is done by replacing the native AudioTrack playback API with a simple wrapper that translates into the libpulse PulseAudio client API. There’s bits of the API that seem to be rarely used(loops and markers, primarily), and I’ve not gotten around to those yet. Basic playback works quite well, and here’s a video showing this. (Note: this and the next video will be served with yummy HTML5 goodness if you enabled the YouTube HTML5 beta). (if the video doesn’t appear, you can watch it on YouTube) Users of PulseAudio might have spotted that this now frees us up to do some fairly nifty things. One such thing is getting remote playback for free. For a long time now, there has been support for streaming audio between devices running PulseAudio. I wrote up a quick app to show this working on the Galaxy Nexus as well. Again, seeing this working is a lot more impressive than me describing it here, so here’s another video: (if the video doesn’t appear, you can watch it on YouTube) This is all clearly work in progress, but you can find the code for the AudioTrack wrapper as a patch for now. This will be a properly integrated tree that you can just pull and easily integrate into your Android build when it’s done. The PA Output Switcher app code is also available in a git repository. I’m hoping to be able to continue hacking on the capture and policy bits. The latter, especially, promises to be involved, since there isn’t always a 1:1 mapping between AudioFlinger and PulseAudio concepts. Nothing insurmountable, though. :) Watch this space for more updates as I wade through the next bit. [Less]