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Kinda fun watching this video. As it seems the big new features of the Windows 7 audio stack are the ability to move streams while they are live, to do role-based policy routing, and to pause streams during phone calls. Hah! That's so yesterday! A certain sound server I happen to know very well has been supporting this for a longer time already, and you can even buy that logic in various consumer products.

Nice to know that in some areas of the audio stack it's not us who need to play catch-up with them, but they are the ones who need to play catch-up with us.

CIO has an interview with me.

LWN covers Paul's and my talk at the Audio MC at LPC, Portland. (Subscribers only for now)

Update: Here's a free subscriber link.

Here are some very short notes from the Audio BoF at the Linux Plumbers Conference in Portland two weeks ago. Sorry for the delay!

Biggest issue discussed was audio routing. On embedded devices this gets more complex each day, and there are a lot of open questions on the desktop, too. Different DSP scenarios; how do mixer controls match up with PCM streams and jack sensing? How do we determine which volume control sliders that are in the pipeline we are currently interested in? How does that relate to policy decisions? Format to store audio routing in?

The ALSA scenario subsystem currently being worked on by Liam Girdwood and the folks at SlimLogic and currently on its way to being integrated into ALSA proper hopefully helps us, so that we can strip a lot of complexity related to the routing logic from PulseAudio and move it into a lower level which naturally knows more about the hardware's internal routing.

Does it make sense for some apps to bypass the ALSA userspace layer and to talk to the kernel drivers via ioctl()s directly?i (i.e. thus not depending on ALSA's LISP intepreter, and a lot of other complexities)? Probably yes, but certainly not in the short term future. Salsa? libsydney?

Should the timing deviation estimation/interpolation be moved from PulseAudio into the kernel? Might be a good idea. Particularly interesting when we try to to monitor not only the system and audio clocks, but the video output and particularly the video input (i.e. video4linux) clocks, too. A unified kernel-based timing system has advantages in accuracy, allows better handling of (pseudo-) atomic timing snapshots, and would centralize timing handling not only between different applications (PA and JACK) but also between different subsystems. Problem: current timing stuff in PulseAudio might be a bit too homegrown for moving it 1:1 into the kernel. Also, depends on FP. Needs someone to push this. Apple does the clock handling in the kernel. How does this relate to ALSA's timer API?

Seems Ubuntu is going to kill OSS pretty soon too, following Fedora's lead. Yay!

And that's all I have. Should be the biggest points raised. Ping me if I forgot something.

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An often asked question is how to properly talk to PulseAudio from within applications where latency matters. To answer that question once and for all I've written this guide in our Wiki that should light things up a little. If you are interested in audio latency in PA, want to know how to minimize CPU usage and power consumption or how to maximize drop-out safety make sure to read this!

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one small note: requiring copyright assignment from contributors, and putting your code in exotic VCSes that only a minority of potential contributors know or are willing to use is not helpful for attracting contributions -- right the contrary, it scares them away. Please fix that!

Last week I've been at the Linux Plumbers Conference in Portland. Like last year it kicked ass and proved again being one of the most relevant Linux developer conferences (if not the most relevant one). I ran the Audio MC at the conference which was very well attended. The slides for our four talks in the track are available online. (My own slides are probably a bit too terse for most readers, the interesting stuff was in the talking, not the reading...) Personally, for me the most interesting part was to see to which degree Nokia actually adopted PulseAudio in the N900. While I was aware that Nokia was using it, I wasn't aware that their use is as comprehensive as it turned out it is. And the industry support from other companies is really impressive too. After the main track we had a BoF session, which notes I'll post a bit later. Many thanks to Paul, Jyri, Pierre for their great talks. Unfortunately, Palm, the only manufacturer who is actually already shipping a phone with PulseAudio didn't send anyone to the conference who wanted to talk about that. Let's hope they'll eventually learn that just throwing code over the wall is not how Open Source works. Maybe they'll send someone to next year's LPC in Boston, where I hope to be able to do the Audio MC again.

Right now I am at the BlueZ Summit in Stuttgart. Among other things we have been discussing how to improve Bluetooth Audio support in PulseAudio. I guess one could say thet the Bluetooth support in PulseAudio is already one of its highlights, in fact working better then the support on other OSes (yay, that's an area where Linux Audio really shines!). So up next is better support for allowing PA to receive A2DP audio, i.e. making PA act as if it was a Headset or your hifi. Use case: send music from from your mobile to your desktop's hifi speakers. (Actually this is already support in current BlueZ/PA versions, but not easily accessible). Also Bluetooth headsets tend to support AC3 or MP3 decoding natively these days so we should support that in PA too. Codec handling has been on the TODO list for PA for quite some time, for the SPDIF or HDMI cases, and Bluetooth Audio is another reason why we really should have that.

Next week I'll be at the Maemo Summit in Amsterdam. Nokia kindly invited me. Unfortunately I was a bit too late to get a proper talk accepted. That said, I am sure if enough folks are interested we could do a little ad-hoc BoF and find some place at the venue for it. If you have any questions regarding PA just talk to me. The N900 uses PulseAudio for all things audio so I am quite sure we'll have a lot to talk about.

See you in Amsterdam!

One last thing: Check out Colin's work to improve integration of PulseAudio and KDE!

Tomorrow, Thu 24th 10 am, there's going to be an Audio BoF at LPC Portland, Salon E. Don't miss it.

A quick update on Skype: the next Skype version will include native PulseAudio support. And not only that but they even tag their audio streams properly. This enables PulseAudio to do fancy stuff like automatically pausing your audio playback when you have a phone call. Good job!

In some ways they are now doing a better job with integration in to the modern audio landscape than some Free Software telephony applications!

Unfortunately they didn't fix the biggest bug though: it's still not Free Software!

Here's a list of quick updates on my mutrace mutex profiler since my initial announcement two weeks ago:

I added some special support for tracking down use of mutexes in realtime threads. It's a very simple extension that -- if enabled -- checks on each mutex operation wheter it is executed by a realtime thread or not. (--track-rt) The output of a test run of this you can find in this announcement on LAD. Particularly interesting is that you can use this to track down which mutexes are good candidates for priority inheritance.

The mutrace tarball now also includes a companion tool matrace that can be used to track down memory allocation operations in realtime threads. See the same lad announcement as above for example output of this tool.

With help from Boudewijn Rempt I added some compatibility code for profiling C++/Qt apps with mutrace, which he already used for some interesting profiling results on krita.

Finally, after my comments on the locking hotspots in glib's type system, Wim Taymans and Edward Hervey worked on turning the mutex-emulated rwlocks into OS native ones with quite positive results, for more information see this bug.

As soon as my review request is fully processed mutrace will be available in rawhide.

A snapshot tarball of mutrace you may find here (despite the name of the tarball that's just a snapshot, not the real release 0.1), for all those folks who are afraid of git, or don't have a current autoconf/automake/libtool installed.

Oh, and they named a unit after me.