Linux-audio-dev

linux-audio-dev@lists.linuxaudio.org

2 participants
7447 discussions

by Jeff McClintock

> From: Fons Adriaensen <fons(a)linuxaudio.org> > On Fri, Feb 18, 2011 at 07:36:44AM +1300, Jeff McClintock wrote: > > > With a RMS VU Meter you measure a 1KHz tone as a reference. > > A contradiction... A VU does not measure RMS, whatever does measure > RMS is not a VU. Isn't a VU Meter a standard root-mean-square function followed by a 300ms integration to give it some 'weight'? ...calibrated against a 1kHz tone?

13 years, 7 months

Calculate R M S

by Alfs Kurmis

Hi Experts. I wanna normalize my sound stream by loudness (energy / pressure / intensity) , not by peaks. How i do it ? Is available Jack plugin for so what ? What is (we hear as) "loudness" ? RMS or +(average) or something else ? Is somewhere available examples how to calculate RMS ? Is it done simlpe by :  int i, n;  double sums, rms;  sums=0.0;  n=10;  rms=0;  for(i=0; i<n;i++)  {   sums = sums + ( (double)i * (double)i );  }  rms = sqrt(sums / n);  printf("          rms = %12.12fnn", rms ); Is so sipmple algo good enough for frequencies > 10 kHz ? How to calculate RMS with hi-precision for frequencies > 10 kHz ? With inerpolation or so ? What is reference ( 0dB ) RMS for example for 16bit PCM signal 1024 samples ?   sqrt( 1024*(0x7FFF ^ 2) / 1024 )  ==  sqrt( (0x7FFF ^ 2)  ) == 0x7FFF  Is it simple  0x7FFF (32000 dec) ? How to calc RMS for stereo signal ? So , or somehow else ? for(i=0; i<n;i++)  {  ....    sums = sampleL/2 + sampleR/2;  } In case operating with float point, what should be a bit faster,  / 2  or * 0.5 ? How to gotta RMS value in dB ?    20 x log10(Measured/Reference0_dB)  or 10 x log10(Measured/Reference0_dB)  ?? Im just physics student and im new in DSP, so pleaz no angree about simple or stuppid questions. Any examples and hints welcomed. Many Tnx in advance. Alf ----

13 years, 7 months

Re: [LAD] Realtime threads and security

by Kjetil S. Matheussen

Paul Davis: > > On Thu, Feb 17, 2011 at 4:53 PM, Robin Gareus <robin(a)gareus.org> wrote: > >>> Aside of that, what about locks? I've many times been told that one mustn't do >>> anything that could block in a realtime thread. What are the consequences of >>> that? Could a malicious app freeze the system by blocking in a realtime thread? > > it poses no risks to anything except itself if it does that. blocking > in an RT thread matters to the thread, not to anything else. > > to demote RT threads that are doing too much you'd need a user-space > watchdog like das_watchdog > Actually, das_watchdog is not very useful anymore after the kernel developers implemented a scheme to avoid a process to take over the machine. This built-in scheme is also a watchdog, but much more fine graided than das_watchdog. And it is also (more often than not) useless, so one has to press the reboot button anyway. The sad thing is that this built-in watchdog in newer kernels fools das_watchdog into thinking that the system is operational. (@#$@#%%!#$$!!!) I should look into it though, it might not be impossible to tune das_watchdog to work again.

13 years, 7 months

Re: [LAD] Calculate R M S (Alfs Kurmis)

by Jeff McClintock

With a RMS VU Meter you measure a 1KHz tone as a reference. Best Regards, Jeff

13 years, 7 months

Devs needed for opensource virtual analog softsynth idea

by Sascha Schneider

Hi folks, inspired by a plan of a german onlinemag called amazona.de I came up with the idea that a virtual analogue opensource softsynth nativly running on Linux would be really nice. (a nice filterbank too, but thats another thing) Amazona planned a complete synth based on userpolls (only in german, sorry): http://www.amazona.de/index.php?page=26&file=2&article_id=3191 which is now realized as vst: (only german, too) http://www.amazona.de/index.php?page=26&file=2&article_id=3202 I know that Zynaddsubfx/yoshimi has a really strong soundengine and I asked myself, if it would be possible to take this engine or the DSSI-API and build a polyphonic softsynth with a nice UI like the new calf plugins or guitarix, a bit like the loomer aspect, with some discoDSP, a bit from the Tyrell or the Roland Gaia SH-01 with midilearn, ...... The problem I have are my programming skills, that are not good enough to code this kind of software by myself. Are there some LAD's willing to join/take/realise this idea?? If there is interest I could translate the ideas of amazona.de and we all could share our visions for a new kind of controllable virtual analogue softsynth. kind regards, saschas

13 years, 7 months

kokkinizita -- correction

by Fons Adriaensen

In a fit or complete braindeadness FA wrote: kokkinizita.linuxaudio.org 198.82.152.114 which should of course have been: 198.82.152.114 kokkinizita.linuxaudio.org Sorry for the confusion !!! -- FA

13 years, 7 months

kokkinizita

by Fons Adriaensen

Hello all, As posted before, kokkinizita.net went offline last week as the result of some stupid but apparently uncorrectable issues with my hosting service, hosteurope.de. They are flatly refusing to put the site back online or allow me to create a new one. The kokkinizita.net domain will appear again (I still own the domain name), but this could take some time. Meanwhile the site has been recreated at <http://kokkinizita.linuxaudio.org>. You won't be able to access it until linuxaudio.org's DNS will be updated to include this url, which will happen some time friday. In the meantime, if you need something urgently, just add the line kokkinizita.linuxaudio.org 198.82.152.114 to your /etc/hosts, but don't forget to remove it later. Many thanks to Robin Gareus, Ico Bukvic and Virginia Tech for providing this solution, and also to all people who suggested alternative hosting. For email, please use the from: address of this message, not the gmail one I posted earlier (I'll still check it, but not as frequently as I do now). Ciao, -- FA

13 years, 7 months

Petri-Foo - have your say!

by James Morris

Hi, I've forked the Specimen sampler to create Petri-Foo[1]. The main goal of Petri-Foo was to make the ADSRs and LFOs independent from the items they modulate (ie amplitude/pitch/etc). This has been achieved and is quite nice to play with switching modulation sources on the go as a sequences plays and the output is recorded. I'm currently overhauling the sample-'editor'. So far I've ported the deprecated GDK drawing code to Cairo, and prettified the display of play start/stop and loop start/stop points and areas. What I want to do next is explained here Sample editor zoom [2] Your ideas would be welcome in how it should work. I'll try and implement it. If you're interested subscribe to the Petri-Foo-Devel list[3]. Please note though, it's not ready for general usage by inexperienced users who don't know how to download and compile software from git repo's nor for users who aren't expecting things to be broken. Thanks, James. [1] http://petri-foo.sourceforge.net/ [2] http://sourceforge.net/mailarchive/message.php?msg_id=27069524 [3] https://lists.sourceforge.net/lists/listinfo/petri-foo-devel

13 years, 7 months

Allocating 96 but reading 16 (multple times)

by Jens M Andreasen

The other day I tried somthing unusual. I use 96 frame buffers and so I allocate two of those for each of in and out, and then read/write (blocking) 96 frames at a time - makes sense, yes? Well no, it turns out that - without doing any processing - looping over read/writing only 16 frames at a time is more robust. How come? The same effect can be observed with 64 frames and 16 appears to be the optimal value in the loop. /j

13 years, 7 months

Fwd: Temporary mail address

by zita kokkini

Hello all, Last week my mail and web host (Hosteurope in Germany) blocked my accound due to failed credit card payments. I got no notice of this until it was too late, and the result is that I can't re-activate my account or even start a new one. For anything urgent you can reach me via the gmail address used to send this messsage. I looking out for a new host, and hope to have the website online before the end of the week. Ciao, -- Fons Adriaensen

13 years, 7 months

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Linux-audio-dev