Linux-audio-dev July 2010

linux-audio-dev@lists.linuxaudio.org

69 participants
72 discussions

by lieven moors

On 07/22/2010 03:36 PM, Fons Adriaensen-2 wrote: > On Thu, Jul 22, 2010 at 09:31:09PM +0200, lieven moors wrote: > > > Hi Fons, I'm a fool to even try to answer this question. > > But I couldn't resist... > > :-) > > > > Let's suppose we have two sounds A and B, > > and sound B has been measured as being twice as loud as A, > > by somebody. In order to be able to say that, that person needs > > some kind of reference measurement unit, the equivalent of a > > measurement stick. That unit has to satisfy two requirements. > > It has to be big enough, so that people can agree some difference > > is being measured, and it has to be small enough, so that a multiples > > of that unit fit into a realistic range. There is a requirement of > maximum > > precision (the smallest value we can measure), and a requirement of > > minimum precision. The question is, what kind of measurement stick > > is being used by that person. > > Not really. If A is 'twice' B, either A or B can act as the reference. Yes, but we can never agree that A is twice B, unless we agree on how precise the measurement could/should be. > > I'm pretty sure that if you'd do the experiment to find out when > people think that an object B is twice as big as another object A > (without introducing optical illusions), you'd find that it's quite > close to a factor of 2. This is because we can easily imagine two > A's side by side, which would be 'twice as big' as one A. I don't think this is easy. Imagine a ruler lying on your desk, and try to imagine the point where the ruler would become twice as long. I think you will find that your brain is continually adjusting that distance, and that it requires significant effort. It also occurs to me, that by doing this, I am actually determining the smallest observable difference, and that this distance is proportionate to the length of the ruler. > > Can we do something similar with 'loudness' ? As I wrote, the > only option I see is to consider two equal sources to be 'twice > as loud' as one of them, but that doesn't work out. It could work if we would agree on it. But apparently our brains have made up their own mind :-) That's why I propose to reconsider how we look at measurement. The process of measuring might not be as simple as we think. > > Given this, what you write does make sense - there must be some > 'stick' rather than a real comparison of A to B. But what is it > based on ? If most people do agree on some value for 'twice as > loud', even with a large variation, there must be some physical > ground for this. But what is it ? And a related question: iff > there is some 'unit' even a variable one depending on frequency > etc., why can't we imagine that unit ? Why don't we 'see' the > stick ? When we see the length of something, we don't see the stick either. The only thing we see is that one thing is longer than the other. The stick is just a short thing, which we can compare to all other things. But even when you agree on such a reference, you still have to go through the process of measuring. The problem of 'twice as loud', shows us that we can measure things even without an agreed-on unit. Somehow we are able to dynamically create that unit when we need it. This is how it could work for example: we have a range, and something within that range: | x | we try to cut the range in halves and keep the part with x: | x | The precision of cutting in halves is based on the smallest observable difference between the two halves, and is proportionate to the size of the range. (yes I know this is a problematic statement, I have to think more about this) We do the same thing again: | x | Now, if we would halve the range again, we would be unable to distinguish x from that point, and we have some kind of measuring stick: | | | | | > > First of all, we can assume that the length of that stick will be > depend > > on the range of possible input values that we observe, and that we want > > to measure. If we want to measure the size of a road, we will probably > > use kilometers, instead of meters. In the same way, when our ears want > > to measure the amplitude of a sound, our ears will use smaller or > bigger > > units, depending on the ranges observed. What are the ranges we > observe? > > Let's assume that humans are perfect, and observe everything that we > > can observe with SPL meters. We could do a statistical investigation > > on a number of people, and make charts of everything they hear. > > In these charts we would see what frequencies they are exposed to, > > and what the minimum and maximum SPL's are for that frequencies. > > After more analyses, we would have one chart that could be > > representative for most people. > > This is basically what has been done more than 50 years ago, with > the known results: the objective ratio corresponding to 'twice as > loud' depends on frequency, absolute level, etc. > > > From that chart we could get an estimate of the size of the measurement > > unit. Frequencies with with bigger SPL variations would be measured > > with bigger units, and visa versa. And from this we could deduce what > > the minimum precision is for a certain frequency, when we say it is > twice > > as loud. To satisfy the requirement of maximum precision, we should > > take into account the smallest observable differences for every > frequency > > in the spectrum. > > 'Smallest observable difference' has been measured as well. It should > relate in some way to 'twice as loud', but I haven't verified this. > OTOH, knowing the smallest observable difference does not help to > define what 'twice as loud' is supposed to be. As I said above, I think it plays a major role, in our ability to measure things Could you elaborate on this a little bit more? Greetings, Lieven > > Another poster mentioned that he found it quite difficult to work > out what 'twice as loud' means for him - and I do believe that is > touching on the real problem: if you start *thinking* about it > rather than just following your 'gut feeling', how sure can you > still be of your impression of 'twice as loud' ? How stable is it > in the face of doubt ? > > Keep on thinking ! > > Ciao, > > -- > FA > > There are three of them, and Alleline. > > _______________________________________________ > Linux-audio-dev mailing list > Linux-audio-dev@... > http://lists.linuxaudio.org/listinfo/linux-audio-dev

14 years, 1 month

Fwd: [tablatures] [Request/Bounty] Tablature bends

by rosea grammostola

---------- Forwarded message ---------- From: Marc Hohl <marc(a)hohlart.de> Date: Sat, Jul 24, 2010 at 8:19 PM Subject: [tablatures] [Request/Bounty] Tablature bends To: Lily-Devel List <lilypond-devel(a)gnu.org>, "tablatures(a)lilynet.net" < tablatures(a)lilynet.net> Hello all, after about half a year I have to admit that I don't have a) the time and b) the programming skills to implement bends in lilypond[1]. Sorry. Bends are important for guitarists, so I offer 75$ for this issue and I am posting to the tablature list, because perhaps someone else there is willing to donate some money too, to get this task done. During winter 2009/2010, Carl and I discussed the syntax and implementation details very intensively in about a dozen mails or so, and as things got nailed down, I wrote a roadmap how the bend engraver and the tab note head engraver have to be built/extended. There is also a file bend.ly which uses slurs to mimic bends - the graphic routines for bends are already there, so I offer my help providing and explaining the roadmap. A skilled developer should have no problems to code the new engraver and transform the graphic routines into c++ code. During the bend.ly story, I got in touch with developers of tuxguitar, so I think the whole bend story will make lilypond more attractive as a front end to tuxguitar users and of course to professional music typesetters working on contemporary guitar music. Greetings Marc [1] It was really hard for me to accept b), but to be honest, I still struggle with some basic concepts of c++ in combination with lilypond, which is *very* frustrating.

14 years, 1 month

One feature, that would be nice for virtual instruments and effects with GUI.

by Mike Cookson

I suggested this idea on linux-audio-dev list: http://lists.linuxaudio.org/pipermail/linux-audio-dev/2010-July/028590.html, but still have no any answers. Unfortunally, as I just saw, it was included into other thread: http://lists.linuxaudio.org/pipermail/linux-audio-dev/2010-July/028588.html, I can guess, it is why there are still no answers. I will not confuse, if this message will also be included into some other thread... At least, you could point me other reasons to not answer to that post. It causes a slight letargy, when question hits into black hole. Initially I planned to make a special controller for Aeolus, which should allow to write stops toggling to sequencer, but then thought, that it is like a sycle building, and a such thing could be more compact - e.g., controller could be integrated into instrument GUI. A feature to generate correct MIDI signal, written to sequencer, could be disabled, even on the fly, to save performance.

14 years, 1 month

Re: [LAD] twice as loud

by lieven moors

...continuation of truncated mail (does anyone know why this happens?) >From that chart we could get an estimate of the size of the measurement unit. Frequencies with with bigger SPL variations would be measured with bigger units, and visa versa. And from this we could deduce what the minimum precision is for a certain frequency, when we say it is twice as loud. To satisfy the requirement of maximum precision, we should take into account the smallest observable differences for every frequency in the spectrum. Greetings, Lieven

14 years, 1 month

mailing list subject line

by lieven moors

Hi everybody, I need some help on using the mailing list. The problem is that I don't know why my posts are creating new threads in the mailing list archives. And I am not sure what the subject line should be, so the post gets attached to the existing thread. I use "Re: subject" in the subject line, but this doesn't seem to be enough (although I think this used to work) Part of the problem might be that I choose not to receive all the mailing list mail in my mailbox. So I am mostly replying to feeds. Thanks for your help, Lieven

14 years, 1 month

JACK Network Manager 0.2.3

by Mike Cookson

JACK NetSource GUI is renamed to JACK Network Manager (jack-netmanager-gtk), since jack_netsource is only a command line front-end for jack netmanager module. Changes: - Name changed from jack-netsource-gui to jack-netmanager-gtk (humany name - JACK Network Manager), since jack_netsource is just a wrapper, controlling jack "netmanager" module. - Presets support, deprecating creation of script with tray support, due to ability to reuse ordinary scripts by JACK Network Manager itself. During of preset saving name is requested and approriate script is stored in presets directory. - Ability to start sources at LADISH rooms. - ladish_launch is deprecated. ladish_control snewapp and rnewapp commands used instead. - Improved desktop launcher - New system tray icons; added application icon, unwantedly removed from 0.2.2 - Fixed help text - Options for jack_netsource from various jack versions are stored in separated file now - Internationalization of bash scripts through gettext - Build system improvements: all text files are configured - e.g., instalation prefix now is working. Configured files are stored into separate build directory, which is autonomous and can be distributed. Also, uninstalation is available. - Internationalization improvements: added update-locales script, which updates template with translations at once, and localization of bash scripts through gettext. Note for distribution maintainers: if you place menu items for special audio software into extra submenus inside standart Audio menu, it would be nice to have JACK Network Manager item in one place with QJackNet (at least) and QJackCtl. And create dummy jack-netsource-gui package for smooth upgrade. Page at GTK-Apps: http://gtk-apps.org/content/show.php/JACK+Network+Manager?content=122327 Latest screenshot is third.

14 years, 1 month

May I asked something OT?

by Ralf Mardorf

A lot of kids wish to have a kill switch for their guitars. A kill switch is a short circuit, to 'stop' the audio signal. I'm not fine with this solution, but the kids argue, that e.g. an interruption does cause unwanted noise, especially for over drive sounds. IMO even using opto-electronics won't solve the issue, because the noise of the transistor overdrive effect still would be hearable, while for a short circuit there is silence. Has anybody an idea to solve this without a short circuit? I'm really not a fan of short circuits. Note, it's not possible to do an interrupt all the times behind the latest noise generator and even an interrupt could cause noise itself, while a short circuit indeed is a good way to cancel sound.

14 years, 1 month

Routing signals in mixer (Ardour, Qtractor)

by Louigi Verona

Hello! Both Ardour and Qtractor are capable sequencers. Ardour is getting midi soon, Qtractor is getting automation. All of this is good news. I was wondering if the devs are interested in implementing routing signals in a mixer as the next important priority. This would allow not only effects chains which is usually very useful, but also usage of vocoders. At the moment it is impossible to use a vocoder plugin inside Ardour or Qtractor. The beauty of vocoders is that they can be used not only on voice, but as electronic instruments as well. I am often using them to create beautiful textures, but in order for the result to be good, I need to automate parameters of the vocoder. LADSPA Vocoder, for instance, is capable of generating very beautiful sounds, but only if you can change the bands in real time, fade the in and out. Of course, sometimes it can be recorded live, but in many cases it needs to be automated and stored in a project. Tell me what you think. -- Louigi Verona http://www.louigiverona.ru/

14 years, 1 month

Re: [LAD] Floating point processing and high dynamic range audio

by lieven moors

On 07/22/2010 05:31 AM, Philipp Überbacher wrote: > Excerpts from Philipp Überbacher's message of 2010-07-22 03:16:00 +0200: > > > Excerpts from fons's message of 2010-07-22 02:24:04 +0200: > > > On Thu, Jul 22, 2010 at 01:05:01AM +0200, Philipp Überbacher wrote: > > > > > > > I think the word loudness is a problem here. Afaik it usually > refers to > > > > how it is perceived, and twice the amplitude doesn't mean twice the > > > > perceived loudness. It may mean twice the sound pressure level, > energy, > > > > or intensity (if we ignore analogue anomalies, as you wrote in > some other > > > > answer). > > > > > > Subjective loudness is a very complex thing, depending on the > > > spectrum, duration, and other aspects of the sound, and also > > > on circumstances not related to the sound itself. > > > > > > For mid frequencies and a duraion of one second, the average > > > subjective impression of 'twice as loud' seems to correspond > > > to an SPL difference of around +10 dB. > > > > I had a brief look at the section about loudness in musimathics and it > > mentions 10 dB based on the work of Stevens, S.S. 1956, > > "Calculation of the Loudness of Complex Noise" and 6 dB based on > > Warren, R. M. 1970, > > "Elimination of Biases in Loudness Judgments for Tones.". > > I think I've encountered the 6 dB more often in texts, which doesn't > > mean it's closer to the truth, if that's possible at all. > > Knowing a 'correct' number would be nice for artists and sound > > engineers, but if it varies wildly from person to person, as Gareth Loy > > suggests (no idea where he bases this on) then this simply isn't > > possible. Picking any number within or around this range is probably as > > good as any other. > > > > > I often wondered what criterion we use to determine which > > > objective SPL difference sounds as 'twice as loud'. We don't > > > have any conscious numerical value (there may be unconscious > > > ones such as the amount of auditory nerve pulses, or the amount > > > of neural activity), so what it this impression based on ? > > > > > > The only thing I could imagine is some link with the subjective > > > impression of a variable number of identical sources. For example > > > two people talking could be considered to be 'twice as loud' as > > > one. But that is not the case, the results don't fit at all (it > > > would mean 3 dB instead of 10). > > > > I never thought about that to be honest. It's immensely complex. It > > might have to do with each persons hearing capabilities, for example > the > > bandwidth of loudness perception or the smallest discernible loudness > > difference. If it really is very different from person to person, then > > an explanation that takes the different hearing capabilities into > > account could be sensible, don't you think? > > I did find some more approaches to the problem, but those are just > ideas. From my personal experience I have to say that I have a very hard > time saying when something is twice as loud. A musically well trained > person might have an easier time, I wouldn't know, but for me twice as > loud is something that is very vague. This might already explain the > large deviation between subjects as described in musimathics. It lead me > to another idea though, the evolutionary perspective. Evolutionary it > likely never was important whether a sound is twice as loud. The only > situation I can imagine where judging loudness probably was important > is judging distances. How far is the animal I can't see, be it prey or > predator, away from me? We know that this takes more than the SPL into > account, and 'twice as loud' doesn't have relevance in this context. So > maybe the loudness perception is linked with spatialization. I think this is a very interesting idea. Could this be linked to some kind of avarage SPL of all the sounds human beings are exposed to (and this variable changes throughout history). Because when we try to judge the distance of a barking dog, our brain would use the knowledge of all other dogs we heard barking before, to estimate the distance of that dog. If we never heard a dog before, maybe we would use the sounds of other animals as a reference, and so on... greetings, Lieven > > My other ideas are rather stupid, just ways to get the right numbers for > your two person idea. > I simply used ln instead of log and got 7, but that's not even Neper and > has no relevance. > > The other idea of that kind is to assume a field quantity, which would > result in 6 dB. I'm still easily confused about 10*log and 20*log, but I > think 20*log is usually used for sound pressure, but maybe not for > psychoacoustic effects. > -- > Regards, > Philipp > > -- > "Wir stehen selbst enttäuscht und sehn betroffen / Den Vorhang zu und > alle Fragen offen." Bertolt Brecht, Der gute Mensch von Sezuan > > _______________________________________________ > Linux-audio-dev mailing list > Linux-audio-dev@... > http://lists.linuxaudio.org/listinfo/linux-audio-dev

14 years, 1 month

"El-Cheapo" software-only equivalent

by rom

Hi all, i'm new to this list. I'd like to ask some advice about a small multitrack recorder program i wrote, and have been using for some time. Basically, what it does is to: - simultaneously capture sound from several consumer-grade soundcards. - use libsamplerate to stretch the audio streams, re-syncing them to the one chosen as "master". The stretch ratio is continuously re-calculated to make the overall frame count of the stretched stream match the overall frame count of the master. - write the "corrected" streams plus the "master" stream to parallel .wav files using libsndfile. The purpose is the same as the quite famous "El-Cheapo Howto" ( http://quicktoots.linuxaudio.org/toots/el-cheapo ), just with no soldering involved :-) Of course, i know the solution is far from perfect, but i use it to record some friends of mine who play in a blues/punk band, and the result is not that bad. Now, the question is: do you think this piece of code can be of any interest for someone out there? Do you think i should i publish it on an open source repository ? Or maybe there's already some other software i'm not aware of, that does the same thing? thanks for your patience, please excuse my bad english. bye alberto

14 years, 1 month

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Linux-audio-dev July 2010