Linux-audio-dev

linux-audio-dev@lists.linuxaudio.org

3 participants
7439 discussions

by Lea Anthony

Hi, I am a musician and also a programmer. I have many years experience of coding but not in the audio field. Any tuts around? How do I get into it? Cheers for any info. -Lea.

21 years, 11 months

Re: [linux-audio-dev] [ann] unmatched - a LADSPA amp tone

by nikodimka

>> You can calculate your tranformation for the input signal S(x_i) once >> And the same transformation for S(x_i)+1 again. > >Won't that just give you the gradient at point x_i, ie. d/dt(S)? yes. >We are talking about frequency domain aliasing here, oh yeah i see. sorry. > which is when you >generate partials that would be above the nyquist frequencyi, so they get >reflected down into low frequencies. It is not directly related to the >differential of the signal, though a high differential is often indicative >of an aliasing problem. > >Typically you prevent audio aliasing by generating the waveform in a way >so that it contains no partials above nyquist, or by generating it at a >sufficiently high sample rate that there are none, then decimating down. but you can do the pretty same trick for the frequencies: take two different numbers with no common divisors (or just a pair of prime numbers) as sampling rates and see how the output signal changes. The difference give you some linear combination of aliased frequencies. __________________________________________________ Do you Yahoo!? Y! Web Hosting - Let the expert host your web site http://webhosting.yahoo.com/

21 years, 11 months

Re: [linux-audio-dev] [ann] unmatched - a LADSPA amp tone

by nikodimka

>> my feeling is that oversampling alone will not do, although >> you're probably right in that it will get rid of most of >> the aliasing. > >Its how most people tackle to problem. I think I can get the valve cheap >enough that it will be practical. I'm not really familiar with what are the techniques of anialiasing in use. But I can see the following way. You can calculate your tranformation for the input signal S(x_i) once And the same transformation for S(x_i)+1 again. I mean two similar input signals differing in one bit of value. So when you have two output saignals you can calculate the error due to aliasing: abs( F(S(x_i)) - F(S(x_i)+1) ) And apply some techniques to eliminate this aliasing ranging from qubic splines to plain dithering applied to the output signal. It seems to me that this is much better than oversampling. Especially for nonlinear transformations. (Or is it just a trivial thing and it doesnt work and this is not what you discuss?) nikodimka > >> i'm thinking about how to apply the technique to produce >> square clipping, or better a [0 .. 1] range of clipping, >> but the integration approach is awkward. > >I doubt that the electronics ever produces hard square clips. __________________________________________________ Do you Yahoo!? Y! Web Hosting - Let the expert host your web site http://webhosting.yahoo.com/

21 years, 11 months

Re: [linux-audio-dev] DJCJ Linux Audio Developers Tech Support database.

by Patrick Shirkey

>Well, I just added myself and discovered the first problem - >you can't change anything after you hit that final submit :-\ >I can guarantee that I will be relocating in the next >4 months. No worries. I/we'll have it more configurable by then. >also, I didn't realize that the "Company Name" is necessary >to get the web URL to show up. I haven't taken this scenario into account. I'll look at fixing it. The data is still available I just have to add an if statement. Actually I'm surprised it didn't show up on the preview. >Good idea, I think. Thanks. This is definitely a work in progress. -- Patrick Shirkey - Boost Hardware Ltd. For the discerning hardware connoisseur Http://www.boosthardware.com Http://www.djcj.org - The Linux Audio Users guide ======================================== "Um...symbol_get and symbol_put... They're kindof like does anyone remember like get_symbol and put_symbol I think we used to have..." - Rusty Russell in his talk on the module subsystem

21 years, 11 months

RE: [linux-audio-dev] Re: image problem [was Re: [Alsa-devel] hel p for a levelmeter]

by Patrick Shirkey

> this is what's on the page: >Creative Labs | Soundblaster Live Platinum | EMU10K1 | Install | >(4)[A][B] > bottom of the page: > >(4) Hardware mixing supported > >... > >NOTE: Just because an I/O is listed does NOT mean it is guaranteed to >be supported. Please check the mailing >list archives before making purchase decisions based on requirements >forIEC958 or ADAT I/O. >[A] IEC958 RCA Input >[B] IEC958 RCA Output >which does not have a lot of informational value (I know what it does >not mean but what does it mean?) and it definitely does not imply there >is a problem of getting the docs to support certain functionality. Hmm. It has a certain informational value although I will concede that when I started getting into alsa these comments were cryptic for me then. They assume a certain level of knowledge is known when referring to the notes. I'll try to think of a way to word it for users who may not have the requisite knowledge. Apart from that at the top of the page it's explicitely stated that some companies have not provided the required docs to enable support for a device. I have always noticed those comments however it may just be my angle on things. I have made some changes to the matrix to be more obvious that even if we have the docs we may not have all the necessary parts. Although I would've thought that most people already know that about Linux hardware support. As you know the known bugs section in the driver notes gives explicit information about things that we know do not work. I'll look making a form for adding specifically to this file. I would like to do that and also make it easier for people to post info about supported devices. I have most of the work done but not finished yet. As it is I currently stay up to 6:00 in the morning many nights of the month. I'm lucky though as I only have to work 16 hours a week in my paying job. I could be working many more hours but have made the decision to sacrifice some of my current earnings in order to build Boost Hardware and DJCJ. Along the way I have also picked up the alsa website :) -- Patrick Shirkey - Boost Hardware Ltd. For the discerning hardware connoisseur Http://www.boosthardware.com Http://www.djcj.org - The Linux Audio Users guide ======================================== "Um...symbol_get and symbol_put... They're kindof like does anyone remember like get_symbol and put_symbol I think we used to have..." - Rusty Russell in his talk on the module subsystem

21 years, 11 months

[linux-audio-dev] DJCJ Linux Audio Developers Tech Support database.

by Patrick Shirkey

I'm pleased to anounce that a database for people willing to provide Tech Suppport to their local community has been setup. The service is free of charge and hosted at http://www.djcj.org/ The purpose of this database is to promote the professional arm of the Linux Audio Developers community. It is intended to be of use to potential clients who may be interested in getting a Linux Audio system working but don't have the time or background knowledge to do the installation or system maintainance? The people and businesses presented in the database are not endorsed or guaranteed by DJCJ.org but they are active members of the Linux Audio Community. Payment for services received is encouraged. Rates are decided by the parties involved. This is intended to be a database for professional tech support. Please let people know about it so that we can show the world we are more than just a bunch of amateurs hacking in our spare time. The database currently provides a very simple interface for adding your contact details and there is also a contact form provided for potential clients to easily get hold of you. Special thanks to Steve Harris and Antti Boman for assistance with the internal code. It is guaranteed that the interface will become much more user configurable over time. Any feedback is welcome and appreciated. -- Patrick Shirkey - Boost Hardware Ltd. For the discerning hardware connoisseur Http://www.boosthardware.com Http://www.djcj.org - The Linux Audio Users guide ======================================== "Um...symbol_get and symbol_put... They're kindof like does anyone remember like get_symbol and put_symbol I think we used to have..." - Rusty Russell in his talk on the module subsystem

21 years, 11 months

Re: Re: [linux-audio-dev] Fwd: Opinions on running VST or DirectX plugins

by chrismorgan＠rcn.com

Just so people don't think the code has fallen off of the face of the planet ;-) Currently I'm working on two things with the wine jack driver , one of which needs to be complete before I submit the patch, the other can wait until some ongoing jack support is complete. 1. The driver currently closes and opens jack connections synchronously with wodOpen and wodClose. The problem is that jack doesn't actually close the clients right away, sometimes it can take many seconds for this to occur. Apparently this is a known jack bug but I'm also wondering if this is a problem in wines pthread implementation of conditions(there is no support for them right now). Either way I've implemented a workaround that basically consists of opening jack connections and marking them as in-use or available as apps open or close audio devices. This behavior can be enabled/disabled via a define in the driver. This isn't complete yet but it should be soon and would prevent the lockups and delays that currently make things a pain. 2. I don't know of an easy way to do resampling so the input audio matches the sample rate that jack expects. What I want is to be able to do something along the lines of: set_sample_rates(input_rate, jack_output_rate); set_resample_algorithm(x); /* pick a reasonable algorithm based on the current cpu and latency requirements */ And then in the callback routine something like: resample(audio_data_in, *audio_data_out); I haven't found anything even close to this simple as of yet, if anyone has any suggestions feel free to mail me about them. There is someone on the jack mailing list working on a resampling library that is supposed to be easy to use and flexable. Either way, this isn't critical although your music sounds funny if your sample rates don't line up very well ;-) Otherwise I'm also looking into a crash with using the jack driver and directsound that might be due to the client process and memory allocation. After working on the arts driver I realized that the future of audio servers really is callback based. It is quite frustrating to see so little use of jack and so much use of poor solutions like direct hardware drivers(alsa/oss) or high latency servers like artsd. No offense intended to people that work on or use either of those audio solutions, it just doesn't make sense when you want to have multiple apps outputting audio at the same time or if you need low latency(high end audio, games?, etc). I'll see what I can do to get things cleaned up and a patch submitted in the next week, conditional of course upon Alexandre accepting jack support into wine. At least now I have someone other than myself with an interest in using jack and wine together ;-) Thanks, Chris > > From: "Kjetil S. Matheussen" <k.s.matheussen(a)notam02.no> > Date: 2002/10/23 Wed PM 12:18:13 EDT > To: linux-audio-dev(a)music.columbia.edu > CC: wine-devel(a)winehq.com > Subject: Re: [linux-audio-dev] Fwd: Opinions on running VST or DirectX plugins > on Linux in real time > > > > On Wed, 23 Oct 2002, Taybin Rutkin wrote: > > > On Wed, 23 Oct 2002, Kjetil S. Matheussen wrote: > > > > > Could it be possible to overcome all problems mentioned just by simply > > > adding jack-support to the wine-server? Then someone could make a simple > > > windows-program for chaining directx and vst plug-ins. > > > > Someone has done this, I believe: > > http://kt.zork.net/wine/wn20021011_139.html#2 > > > Wow, it allready exist. Hey, wine-people, this driver is really needed for > real-time audio-work, and for programs as sound-editors, multitrackers > and interactive dsp programs as pd, jmax, and a lot of others. Artsd > (f.ex) is not an alternative in its current form, and probably never will > be either. Its something else. I guess Paul or some other competant person > can explain a bit more why jack is so important. > > > -- > > > > >

21 years, 11 months

RE: [linux-audio-dev] Re: image problem [was Re: [Alsa-devel] hel p for a levelmeter]

by STEFFL, ERIK (SBCSI)

> -----Original Message----- > From: Patrick Shirkey [mailto:pshirkey@boosthardware.com] > Sent: Wednesday, October 23, 2002 11:38 AM > > >> Plus the sound matrix at > >> http://www.alsa-project.org/alsa-doc/ doesn't say there > are problems > >>getting docs from manufacturer. > > >Perhaps someone should add a note. > > I thin there is right at the bottom of the page. But I will > make a more > noticible note. this is what's on the page: Creative Labs | Soundblaster Live Platinum | EMU10K1 | Install | (4)[A][B] bottom of the page: (4) Hardware mixing supported ... NOTE: Just because an I/O is listed does NOT mean it is guaranteed to be supported. Please check the mailing list archives before making purchase decisions based on requirements for IEC958 or ADAT I/O. [A] IEC958 RCA Input [B] IEC958 RCA Output which does not have a lot of informational value (I know what it does not mean but what does it mean?) and it definitely does not imply there is a problem of getting the docs to support certain functionality. > > professional system or not, I would expect it to be > capable running > >browser and mp3 player at the same time (even though I would not > expect >this capability to be used in studio work). > > AFAIK this is possible if you use kde or gnome as your > desktop and don't > mind having artsd block the interface. Many other desktops > support artsd ? it's not desktops but applications that need to support sound server. you mean that the sound server is not installed as part of that dektop environment? > also but they are usually not installed by default. Hence > anyone who can > install an alternative desktop should also be willing to > get the sound > server running if they desire that functionality. This has > been the case > for at least the past three years. yes, sound servers can be used with certain application, but what is needed is something that supports ALL applications (or more precisely, that is supported by all applications), or at least does not prevent other applications from working (jack might turn out to be the solution - once it's as good as planned it might become the only player in town) erik

21 years, 11 months

Re: [linux-audio-dev] Re: image problem [was Re: [Alsa-devel] hel p for a levelmeter]

by Patrick Shirkey

>> Plus the sound matrix at >> http://www.alsa-project.org/alsa-doc/ doesn't say there are problems >>getting docs from manufacturer. >Perhaps someone should add a note. I thin there is right at the bottom of the page. But I will make a more noticible note. > professional system or not, I would expect it to be capable running >browser and mp3 player at the same time (even though I would not expect >this capability to be used in studio work). AFAIK this is possible if you use kde or gnome as your desktop and don't mind having artsd block the interface. Many other desktops support artsd also but they are usually not installed by default. Hence anyone who can install an alternative desktop should also be willing to get the sound server running if they desire that functionality. This has been the case for at least the past three years. -- Patrick Shirkey - Boost Hardware Ltd. For the discerning hardware connoisseur Http://www.boosthardware.com Http://www.djcj.org - The Linux Audio Users guide ======================================== "Um...symbol_get and symbol_put... They're kindof like does anyone remember like get_symbol and put_symbol I think we used to have..." - Rusty Russell in his talk on the module subsystem

21 years, 11 months

RE: [linux-audio-dev] Re: image problem [was Re: [Alsa-devel] hel p for a levelmeter]

by STEFFL, ERIK (SBCSI)

> -----Original Message----- > From: Taybin Rutkin [mailto:trutkin@physics.clarku.edu] > > On Tue, 22 Oct 2002, STEFFL, ERIK (SBCSI) wrote: > > > except of the blocking of sounds (the problem mentioned > above) I am quite > > dissapointed by functionality of linux drivers I have > tried, I have sb live > > platinum and (last time I checked): > > Maybe you should buy cards from companies that care about > Linux support. and which are those? I know of no way to get information about how good/complete the alsa driver is. I have read number of thread on various mailing lists/forums etc. about which cards to use (for different purposes) and I didn't find any useful information... The docs at alsa site are pretty much useless for this purpose (as far as I can tell). BTW creative provides some linux support. Plus the sound matrix at http://www.alsa-project.org/alsa-doc/ doesn't say there are problems getting docs from manufacturer. > You seem to be forgetting that most of the drivers are written by > volunteers working without documentation. no I don't. I am not saying somebody should go and fix my problems. I was just ranting because I am frustrated and I hope it will provide semi-useful feedback to somebody... (and somebody will go and fix my problems:-) possibly... and we were talking about acceptance of linux audio. erik

21 years, 11 months

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Linux-audio-dev