Re: [LAD] jack ringbuffer question
Sean Bolton wrote: On Dec 2, 2009, at 7:33 AM, lieven moors wrote: Paul Davis wrote: On Tue, Dec 1, 2009 at 9:51 PM, lieven moors lievenmo...@gmail.com wrote: I want to repeat the same Arp, until there is an update to the text file. One arp is allready loaded in each ringbuffer in main(). When the file is modified, a second one is added, and process skips to the second one. Since I have only space for two arps in the buffer, there should always be exactly one which is readable. I know it is a bit weird, but it seems to work, apart from the problem I described. sounds as if you might want to look into atomic pointer and/or integer exchange instead, to get lock-free double buffering. ringbuffers are generally for passing streaming data/events. Could you give me a hint on how to use atomic pointers? Should I use __sync_val_compare_and_swap from GCC? I've been looking around for other libraries, but I'm not sure where to start. Also, what did you mean with 'integer exchange'? Is it yet another way of using CAS? All of that stuff is great to learn about, but on the other hand, you've already got the hang of the ringbuffer API -- why not just use that? The way I usually deal with this sort of thing is to have two ringbuffers, one from the worker thread to the process thread, and one from the process thread back to the worker thread. Worker (inotify) thread creates a new Arp, and passes a pointer to it through the ring buffer to the process thread. Process thread then reads the new Arp pointer from the first ringbuffer, begins to use it, and passes a pointer to the old Arp back through the second ringbuffer to the worker thread. Worker thread then reads the old Arp pointer from the second ringbuffer, and frees or reuses it. Disadvantage to this is it's not quite as efficient as an atomic pointer exchange, but the advantage is you've already got everything you need right there in jack, no need for an extra library. HTH, -Sean Thanks very much for your reply! I was reluctant to start using atomic pointers, because I might change the program later to read longer sequences of Arps. So the ringbuffer approach might be a good choice after all. I think your idea is exactly what I was looking for. Thanks again, Greetings, Lieven P.S. I would love to see a simple (maybe fake) example of how to use atomic pointers though, because I only have a vague idea of how they are used in practice... Anyone? ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
Re: [LAD] jack ringbuffer question
On Thu, Dec 3, 2009 at 8:14 AM, lieven moors lievenmo...@gmail.com wrote: Thanks very much for your reply! I was reluctant to start using atomic pointers, because I might change the program later to read longer sequences of Arps. So the ringbuffer approach might be a good choice after all. I think your idea is exactly what I was looking for. I was going to suggest the same exact thing as Sean. With the 2 ringbuffers, you're guaranteed that your RT thread is no longer looking at the old Arp object. You're basically implementing message passing, while still taking advantage of the threads' shared memory (where the Arp object resides). With an atomic pointer swap, I don't think you're guaranteed that. Each access to the address of the old Arp object would be atomic, but isn't it still possible that the RT thread reads the old pointer value, is pre-empted, the other thread swaps the pointers, then the RT threads tries to access memory a few bytes from the old pointer it read? ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
Re: [LAD] [LAU] [LAA] [ANN] guitarix-0.05.2-1 released
Am Donnerstag, den 03.12.2009, 14:04 +0100 schrieb Hartmut Noack: hermann schrieb: I'm happy to announce a new guitarix release guitarix is a simple Linux Rock Guitar amplifier and is designed to achieve nice thrash/metal/rock/blues guitar sounds. Guitarix uses the Jack Audio Connection Kit as its audio backend and brings in one input and two output ports to the jack graph. Nice one, thatnk you :-) I love to see this project grow - a simple works-right out of the box amp for Linux is extremely welcome. BTW: do you think, you could turn it into a LV2-plugin? Some people could consider then to boost stability and performance of their Linux audio system by dropping VST via WINE Thanks Hartmut, good to hear that you like it. :-) Make guitarix a LV2-plugin, is at least a question of development power. We would love that to, but, Guitarix is a young small project, we are only 2 developers, and we both have at first other tasks in mind witch we wone implement. In fact, it will be easy for a bit experienced LV2 developer to port the control chain of guitarix to LV2. Our source is spiked with comments witch make it easy to jump in and grep the needed source. Guitarix is a open Project, open for developers who wone join the project. gruß hermann ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
[LAD] Milivoltmeter - Was FOSS Ethernet Soundcard
On Wed, 2 Dec 2009 17:19:30 + Folderol folde...@ukfsn.org wrote: On Tue, 1 Dec 2009 21:46:32 +0100 (CET) k...@aspodata.se (Karl Hammar) wrote: Folderol: ... My new millivoltmeter/dB meter is nearly finished - All I need now is precision resistors 9M, 900k, 90k :? ... Can you publicise it so I can build me one also? Regards, /Karl It is simple enough, so as soon as I can find the time I'll draw out the schematic and post it here as a PDF attachment. As promised, PDF attached. I haven't had time to make out any explanatory notes, but I think it's pretty straight forward anyway 0dB is variable so it can be set to whatever is convenient, hence temperature drift from using an ordinary diode as a reference is not important. -- Will J Godfrey http://www.musically.me.uk Say you have a poem and I have a tune. Exchange them and we can both have a poem, a tune, and a song. Meter.pdf Description: Adobe PDF document ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
Re: [LAD] Milivoltmeter - Was FOSS Ethernet Soundcard
On Thu, Dec 03, 2009 at 10:29:54PM +, Folderol wrote: As promised, PDF attached. Mmmm. Just 1 picofarad of stray capacitance on the switch and wiring, in parallel with 9M, will create a filter with its 3 dB frequency in the audio band. And 1 pf is really nothing, expect more. This will lead to gross errors at anything but the lowest frequencies. Is there any reason why an audio level meter should have such a high input impedance ? Ciao, -- FA Wie der Mond heute Nacht aussieht ! Ist es nicht ein seltsames Bild ? ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
Re: [LAD] [LAA] [ANN] guitarix-0.05.3-1 quick release
Hi, Being a user of Debian Stable, the dependency on gtk+-2.14 is not good. I've uploaded a patch which will get guitarix built against gtk+-2.12 on Debian Stable - but it's utterly untested. (side note: I did not know what to replace gtk_menu_get_accel_path with, so used an empty string .) http://jwm-art.net/art/text/guitarix-0.05.4-1_gtk2.12.patch Hope it helps the Debian Stable users out there who don't want to upgrade their gtk right now. james. On 2/12/2009, hermann brumm...@web.de wrote: This is a quick guitarix update to cover the new release of jconvolver eg. jconv guitarix is a simple Linux Rock Guitar amplifier and is designed to achieve nice thrash/metal/rock/blues guitar sounds. Guitarix uses the Jack Audio Connection Kit as its audio backend and brings in one input and two output ports to the jack graph. To cover the renaming of jconv to jconvolver, guitarix-0.05.3-1 looks now first for jconvolver, if it isn't installed, it looks for jconv. Also a patch from Michal Seben (OpenSuse) is added to cover a build fail at openSUSE:Factory. Thanks Michal. :-) Additional, there is a (rt) 2 Channel delay chooser for the output to jconv, and the Chorus effect work in Stereo now. have fun Project page with screenshots: http://guitarix.sourceforge.net/ download: http://sourceforge.net/projects/guitarix/ For capture, guitarix uses the external application 'jack_capture' (version = 0.9.30) written by Kjetil S. Matheussen. If you don't have it installed, you can look here: http://old.notam02.no/arkiv/src/?M=D For extra Impulse Responses, guitarix uses the convolution application 'jconv' created by Fons Adriaensen. If you don't have it installed, you can look here: http://www.kokkinizita.net/linuxaudio/index.html I(hermann) use faust to build the prototype and will say thanks to : Julius Smith http://ccrma.stanford.edu/realsimple/faust/ : Albert Graef http://q-lang.sourceforge.net/examples.html#Faust : Yann Orlary http://faust.grame.fr/ guitarix is licensed under the GPL. regards Hermann Meyer James Warden -- ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
Re: [LAD] Milivoltmeter - Was FOSS Ethernet Soundcard
On Thu, 3 Dec 2009 23:52:03 +0100 f...@kokkinizita.net wrote: On Thu, Dec 03, 2009 at 10:29:54PM +, Folderol wrote: As promised, PDF attached. Mmmm. Just 1 picofarad of stray capacitance on the switch and wiring, in parallel with 9M, will create a filter with its 3 dB frequency in the audio band. And 1 pf is really nothing, expect more. I use the old fashioned method of wiring resistors directly on standard glass loaded wafer switches. Initial tests suggest the bandwidth well exceeds 20kHz - as opposed to less than 1kHz for many quite expensive commercial units. This will lead to gross errors at anything but the lowest frequencies. Is there any reason why an audio level meter should have such a high input impedance ? No reason at all, except that being a cheapskate I was able to convince the boss that a good true RMS meter would be useful in the workshop :) A 10M input is more-or-less mandatory in this case, but anyone else should feel free to make the ladder impedance whatever they like. -- Will J Godfrey http://www.musically.me.uk Say you have a poem and I have a tune. Exchange them and we can both have a poem, a tune, and a song. ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
Re: [LAD] Milivoltmeter - Was FOSS Ethernet Soundcard
On Thu, Dec 03, 2009 at 11:13:05PM +, Folderol wrote: I use the old fashioned method of wiring resistors directly on standard glass loaded wafer switches. Initial tests suggest the bandwidth well exceeds 20kHz - as opposed to less than 1kHz for many quite expensive commercial units. They are not so 'standard' today, and probably difficult to find. Bandwidth will not be the problem. What you get is a filter that will boost HF. 1 pf = +3dB at 17.7 Khz on all but the 20 mV range. 10 pf means +3dB at 1.77 kHz, and rising. A 10M input is more-or-less mandatory in this case, but anyone else should feel free to make the ladder impedance whatever they like. Even a 1M input would require at trimmer across the 0.9M resistor and fixed Cs for the others. The only reliable way to have 10M is to use an external calibrated probe feeding into a standard 1M input (which then will need a calibrated capacitance as well). Ciao, -- FA ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
Re: [LAD] Milivoltmeter - Was FOSS Ethernet Soundcard
Looking at the pdf, the voltmeter looks functional. Maybe the front end can be tweaked, but this a problem of most test instruments. Last I saw, good probes that match a decent input cost a lot of money; maybe more then the voltmeter in this case. Anyway, thanks for the schematic Will. And thanks for the (somewhat)constructive help on the circuit Fons. ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
[LAD] L2Ork story on Slashdot brings up the age-old question whether Linux is ready for serious audio use
Dear fellow FOSS enthusiasts, This is probably already old news according to Internet standards but as it turns out we spent a good time this evening in class not knowing that we got slashdotted. For those interested in belatedly joining the discussion, please visit: http://entertainment.slashdot.org/story/09/12/03/2018253/Introducing-L2Ork-W orlds-First-Linux-Laptop-Orchestra Best wishes, Ivica Ico Bukvic, D.M.A. Composition, Music Technology Director, DISIS Interactive Sound Intermedia Studio Assistant Co-Director, CCTAD CHCI, CS, and Art (by courtesy) Virginia Tech Dept. of Music - 0240 Blacksburg, VA 24061 (540) 231-6139 (540) 231-5034 (fax) i...@vt.edu http://www.music.vt.edu/faculty/bukvic/ ___ Linux-audio-dev mailing list Linux-audio-dev@lists.linuxaudio.org http://lists.linuxaudio.org/mailman/listinfo/linux-audio-dev
