Linux-audio-dev February 2011

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Faust MIDI?

by Carlo Capocasa

Hi, is it possible to send and receive MIDI with a FAUST program? Carlo

12 years, 4 months

RDF libraries, was Re: [ANN] IR: LV2 Convolution Reverb

by Chris Cannam

On 23 February 2011 22:11, David Robillard <d(a)drobilla.net> wrote: > SLV2 is now based on two new libraries: Serd (RDF syntax) and Sord (RDF > store). Both are roughly 2 thousand lines of C, solid and thoroughly > tested (about 95% code coverage, like SLV2 itself). Serd has zero > dependencies, Sord depends only on Glib (for the time being, possibly > not in the future). Can you point me at the API or code? I couldn't see it in a quick browse on your SVN server. I have a library (Dataquay, http://code.breakfastquay.com/projects/dataquay -- preparing a 1.0 release of it at the moment, so if anyone wants to try it, go for the repository rather than the old releases) which provides a Qt4 wrapper for librdf and an object-RDF mapper. It's intended for applications whose developers like the idea of RDF as an abstract data model and Turtle as a syntax, but are not particularly interested in being scalable datastores or engaging in the linked data world. For my purposes, Dataquay using librdf is fine -- I can configure it so that bloat is not an issue (and hey! I'm using Qt already) and some optional extras are welcome. But I can see the appeal of a more limited, lightweight, or at least less configuration-dependent back-end. I've considered doing LV2 as a simple example case for Dataquay, but the thought of engaging in more flamewars about LV2 and GUIs is really what has put me off so far. In other words, I like the cut of your jib here. Chris

13 years

Petri-Foo - a new fork of Specimen

by James Morris

Hi, I've forked Specimen primarily to provide frequency Modulation of the LFOs and to make all the LFOs and ADSRs independent so that there is no longer a single dedicated ADSR and a single dedicated LFO for ie pitch modulation, but two 'inputs' for pitch modulation for which the choice of all ADSRs and all LFOs is available. Please read the README for more information: https://github.com/jwm-art-net/Petri-Foo#readme The current state of Petri-Foo is that the LFOs and ADSRs have been made independant and are, AFAICT, working as should. The GUI is not yet up to date, but changes have been made enough to get a basic idea of what's going on. Please do read the README before commenting. I've tried to do things properly! I'm only human and only a hobbyist coder. Cheers, James. -- _ : http://jwm-art.net/ -audio/image/text/code/

13 years, 4 months

Finding Deadlock causes in multithreaded C++ using gdb

by Harry Van Haaren

Hey guys, I'm working on a mulithreaded version of my pet project, and I've now managed to deadlock one thread, which in turn makes the GUI thread wait for a mutex lock, and then finally segfaults the whole program :-) So I'm looking for pointers on how best to find a deadlock's cause using gdb? Other advice / good articles on the topic etc welcome! Thanks for reading, -Harry

13 years, 6 months

Re: [LAD] [patch] Re: autogroup: sched_setscheduler() fails

by torbenh

sorry... i cced the old ML addresses :S fixing the CC now. On Mon, Feb 28, 2011 at 07:29:54PM +0100, Mike Galbraith wrote: > On Mon, 2011-02-28 at 18:53 +0100, torbenh wrote: > > > > On Tue, Feb 22, 2011 at 03:47:53PM +0100, Mike Galbraith wrote: > > > On Tue, 2011-02-22 at 13:24 +0100, torbenh wrote: > > > > On Fri, Feb 18, 2011 at 01:50:12PM +0100, Mike Galbraith wrote: > > > > > > > Sounds like you just want to turn CONFIG_RT_GROUP_SCHED off. > > > > > > > > but distros turn it on. > > > > we could prevent debian from turning it on. > > > > now opensuse 11.4 has turned it on. > > > > > > If you or anyone else turns on RT_GROUP_SCHED, you will count your > > > beans, and pay up front, or you will not play. That's a very sensible > > > policy for realtime. > > > > this probably means that generic computer distros should not turn this > > option on ? > > Yeah, agreed, not for a great default config, but only because > newfangled automation thingies can't (possibly?) deal with it sanely. but this is excactly the reason, why i would advocate rt_runtime to be in a separate cgroups system. any admin who wants to limit RT runtime could still do it. people who dont care, and just want their cfs slices configured, can still do it. > > > > If systemd deals with it at all, seems to me it can only make a mess of > > > it. But who knows, maybe they made a clever allocator. If they didn't, > > > they'll need an escape hatch methinks. > > > > the problem is that audio applications can not really pre allocate their > > cpu needs. user can add processing plugins until he pushes his machine > > to the limit. (or the cgroup where his process is running in) > > > > we dont really have a mechanism for plugins to publish their needed > > cycles. > > I can't see how it could matter what any individual group of arbitrary > groups N (who can appear/disappear in the blink of an eye) advertises as > it's wish of the instant. "Hard" + "Arbitrary" doesn't compute for me. i dont really understnad this statement. > > -Mike > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo(a)vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ -- torben Hohn

13 years, 7 months

[ANN] IR: LV2 Convolution Reverb

by Tom Szilagyi

Hi all, Standing on the shoulders of giants[*], I am pleased to announce the public release of IR, a convolution reverb in the LV2 plugin format. Released as free software under the GNU GPL, this easy to use plugin has been created to open the fascinating world of convolution reverb to Linux-based audio engineers. If you use Ardour to create, mix & produce music, you will most probably want to check out this plugin. Assorted features: * Zero-latency operation * Support for mono, stereo and 'True Stereo' (4-channel) impulses * Realtime operation * Very reasonable CPU consumption * Maximum impulse length: 1M samples (~22 seconds @ 48kHz) * Loads a large number of audio file formats * High quality sample rate conversion of impulse responses * Stretch control (via high quality SRC in one step integrated with impulse loading) * Pre-delay control (0-2000 ms) * Stereo width control of input signal & impulse response (0-150%) * Envelope alteration with immediate visual feedback: Attack time/percent, Envelope, Length * Reverse impulse response * Autogain: change impulses without having to adjust 'Wet gain' * Impulse response visualization (linear/logarithmic scale, peak & RMS) * Easy interface for fast browsing and loading impulse responses IR should work on Linux with Ardour 2.8.x (x >= 11) and 3. For further info and source code download, please visit the plugin's homepage: http://factorial.hu/plugins/lv2/ir Thanks, Tom [*] Fons Adriaensen (zita-convolver), Erik de Castro Lopo (libsndfile, libsamplerate)

13 years, 7 months

LAD Activity (WAS: [ANN] IR: LV2 Convolution Reverb)

by Stefano D'Angelo

2011/2/23 Alexandre Prokoudine <alexandre.prokoudine(a)gmail.com>: > On 2/22/11, David Robillard wrote: > >> I have a working plugin (called "dirg") that provides a UI by hosting a >> web server which you access in the browser. It provides a grid UI either >> via a Novation Launchpad, or in the browser if you don't have a >> Launchpad. Web UIs definitely have a ton of wins (think tablets, remote >> control (i.e. network transparency), etc.) >> >> I also have a complete LV2 "message" system based on Atoms which is >> compatible with / based on the event extension. Atoms, and thus >> messages, can be serialised to/from JSON (among other things, >> particularly Turtle). > > Any of them available to have a look at? > >> Currently dirg provides the web server on its own with no host >> involvement, but every plugin doing this obviously doesn't scale, so >> some day we should figure this out... first we need an appropriately >> high-level/powerful communication protocol within LV2 land (hence the >> messages stuff). > > Where do you stand with priorities now? That sounds like something > very much worth investing time in. > > You see, one thing I'm puzzled about is that you have beginnings of > what could be significant part of a potentially successful cloud > computing audio app, and then you talk about how donations don't even > pay your rent :) Before I totally forget about it... I think it might be a very clever thing to do to have some web-based thing (wiki or whatever, ideally a social network kind of thing) were LAD people can notify of what they are working on and what are their plans, so that it's easier to: a. know about it and b. start cooperations, etc. For example, Dave is doing lots of stuff that I plan to reuse, but I only know it because I happen to lurk on #lv2 on freenode from time to time, and the same goes for lots of stuff I'm seeing coming out lately. If it is a problem for me to keep up to date with this stuff, I can only imagine what it would be like for a newcomer. I can't comment on this more now, but please somebody consider the idea. Stefano

13 years, 7 months

Realtime threads and security

by Olivier Guilyardi

Hi everyone, I am currently spending a lot of time working on Android, and on the andraudio mailing list [1] we are discussing about possible improvements to the internal Android audio system. Currently, latencies are very high, over 100ms, and we're looking for ways to improve the situation. In my opinion this can't be achieved on Linux without realtime scheduling. On Android, there's something called audioflinger which acts as a sound server, and apps act as clients of this server. The server and clients run in distinct processes. What I'm thinking about is having a realtime thread within the server, as well as another realtime thread in the (each) client. The one thing about Android is that it has a strict security model. Every app is considered potentially harmful and is thus "sandboxed". Here, this for example means that apps can lower their threads priority, but not increase it. And of course they can only use non-realtime scheduling. On desktops, for instance using JACK, apart from a few multimedia distributions, realtime permissions are not granted by default to normal users. And when one enables it, security is usually not a primary concern AFAIK. If a piece of software happens to crash the system when running in realtime, the user may just uninstall the buggy software, etc.. But on phones, this is critical, for example if the system crashes while you're waiting for a call. So, on Android, the security policies are strict. But this could certainly be necessary to plenty of other Linux usages. Now my question is: how to allow user-space apps to use realtime scheduling for one of their threads without compromising the overall security? For example, in man sched_setcheduler() I see SCHED_RR, and "Everything described above for SCHED_FIFO also applies to SCHED_RR, except that each process is only allowed to run for a maximum time quantum". Would this help and be sufficient? Would there need to have some kind of watchdog/monitor running with SCHED_FIFO scheduling to prevent realtime client threads from consuming too much resources? Or is there some other ways to achieve this? Some kernel patch maybe? Thanks in advance [1] http://music.columbia.edu/mailman/listinfo/andraudio Olivier

13 years, 7 months

Lexicon MX300 console for Linux

by jani＠lasipalatsi.fi

Hi, I've written a small program (Leevi is its name) to drive Lexicon MX300, similar console what Lexicon ships for Windows operating system along with their devices. Leevi supports Linux and BSD, and needs either libusb-0 or libusb-1. It does not require any user interface libraries, as everything is built on libX11, so if you can boot to runlevel 5, you can run Leevi. Please note: As Lexicon wasn't very keen to tell me how to talk with their devices, USB protocol is reverse engineered by me and there are myriad of things that I haven't yet revealed. Although Leevi is proven to work without breaking anything, there is always a small change that something goes wrong. Therefore I don't take any responsibility, you use Leevi at your own risk. Check BSD License in Leevi's homepage. Leevi is yet in development stage, changing effect in stereo mode and changing routing to/from stereo does not yet work. All other features should be fully functional. http://leevi.sourceforge.net - Jani Salonen

13 years, 7 months

Writing an IEEE 802.1BA (AVB) compliant network backend for Jack2

by Christoph Kuhr

Hi list, i want to write a jack2 network backend, like netjack2, for my bachelor thesis. There is a new network standard comming up specialized for audio and video transmission, called AVB (Audio Video Bridging -> IEEE 802.1AS, 802.1Qat, 802.1Qav,...). I want do integrate this standard into jack2. I want to choose AVB (not ALSA or NET) from the driver dropdown box. does anyone know where i can find this implementation in the source code?

13 years, 7 months

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Linux-audio-dev February 2011