Linux-audio-dev

linux-audio-dev@lists.linuxaudio.org

3 participants
7520 discussions

job posting: ALSA/gstreamer/linux/C++/FOSS Indiana, USA

by Paul Davis

I'm forwarding a job posting sent to me by the recruiter. I'd like to do this myself, but the time and location make it infeasible. Apparently, there are some options for remote work but I'm not clear what they are. Talk to the recruiter to find out more. --p ---------------------------------------------------------------------------------------------- Tom Gugger Independent Recruiter tgugger(a)bex.net Linux Audio/ Contract/ Immediate/ IN Skills: linux ubuntu embedded alsa gstreamer cm synergy c++ This is an eight month contract in Kokomo, Indiana. If you fit the job description below, email your resume to tgugger(a)bex.net. Make sure your resume shows the required skills. No ALSA type experience, no job. ALSA = Linux Audio Package Experience Duties in this role include: - Design SW Architecture for Linux and audio subsystem - Detailed task planning and estimating - Linux package management, integration and direction THIS IS A 6-8 MONTH CONTRACT OPPORTUNITY Requirements - Linux Audio Package experience (ALSA source/sink, GStreamer architecture) - Linux Kernel understanding - Ability to reconfigure and rebuild kernel and kernel modules - C++ Object Oriented design, analysis - Linux Driver architecture understanding - It is preferable that the person has contributed to Open Source development (FOSS project) - CM experience required. Synergy experience preferred.

15 years

Re: [LAD] Meego pulseaudio "compliance" and "enforcement" (was Re: [Meego-handset] Enabling Speakerphone)

by Niels Mayer

Marco -- many thanks for your reply -- I've taken the liberty of CC'ing this informative reply to the Linux-Audio-Developers list (your CC was not posted as you're not a subscriber: http://lists.linuxaudio.org/pipermail/linux-audio-dev/2010-December/thread.… ). The list comprises a good number of people with expertise in both pulseaudio; hopefully the Jack sound server authors, including Paul Davis, will be willing to publicly share their perspectives on the issues raised regarding the role of pulseaudio on a handset and Linux audio performance/latency/efficiency issues. Here's a link to Marco's original post to meego-handset mailing list, forwarded below: http://lists.meego.com/pipermail/meego-handset/2010-December/000090.html ---------- Forwarded message ---------- From: Marco Ballesio <gibrovacco> Date: Sat, Dec 18, 2010 at 4:42 AM Subject: Re: Meego pulseaudio "compliance" and "enforcement" (was Re: [Meego-handset] Enabling Speakerphone) To: Niels Mayer <nielsmayer> Cc: meego-handset(a)lists.meego.com, Linux Audio Developers <linux-audio-dev(a)lists.linuxaudio.org> [...] Hi, sorry for the late reply but, whew, this was really long, definitely more than what my poor brain can handle in a single bunch ;). Maybe we could split this into a "Resource Policy Framework" and "Pulseaudio on Embedded" couple of threads. As a general comment on PA, it may appear odd but when I started working with it I shared 100% of your considerations. Working with it (not ON it), I started realising that, ok, it may not be perfect (and which software actually is?) but it brings definitely more benefits than troubles to the system. See my notes below for more details. ..snip.. > > Hopefully there's more than just source-code to describe the policies > and enforcement. Maybe you've read in some other of my posts here and there, I'm trying to get a Resource Policy Framework wiki somewhere. In the meanwhile, documents are scarce but present: - The MeeGo conference presentation: http://conference2010.meego.com/session/policy-framework-flexible-way-orche… Does not say too much, but it comes with some slides and many "mmmmh" (keepalive signals). - The resource policy application developer's manual: http://wiki.meego.com/images/Meego-policy-framework-developer-guide.pdf Mysteriously, it's not linked or referred to anywhere.. at least, now it's on this thread. - The source code: it may twist more than one nose but, at the end, I always like to check in the sources before/after Googling. Documents may be obsolete (who knows?) or expose a partial view. Code can't ;). Not that I want to say with this that we don't need more documents about the Resource Policy Framework... > Is there a design document stating the > "organizational" or "legal" or "human" reasons for said policies and > enforcements? My pointers of above may begin to satiate your hunger (appetisers?). > > And, as a developer, where is the documentation for the appropriate > layer to use, the appropriate API, etc -- e.g. for the original > question that started this thread -- how to switch on/off speakers, > FM-radio transmitter, etc on handset. ( cf my original reply > http://lists.meego.com/pipermail/meego-handset/2010-December/000066.html > ) Unfortunately, this is still in the "dark side" of the documentation, which is currently application-centric. Hopefully one day we'll have an "Adaptation developer's guide", in the meanwhile, a good starting point may be checking the sources, the N900/Meego ruleset and posting questions here. If it's not enough, we may set up an IRC channel (if there's enough interest)... > > Something high-level like the following Maemo document would be very > helpful -- but I have been unsuccessful finding such documentation for > Meego: http://wiki.maemo.org/Documentation/Maemo_5_Developer_Guide/Architecture/Mu… See my notes above about the project wiki. Your pointers are definitely good hints, thanks. > > Also, why not use ALSA use-case-manager: > http://opensource.wolfsonmicro.com/node/14 > UCM appears to be scheduled for other distros "handset" work: > https://wiki.ubuntu.com/Specs/N/ARM/AlsaScenarioManager this project covers the audio-specific cases: for what I understood it might very well be used as an ALSA enforcement point in the Framework so, more than compete with Resource Policy it would be complementary in case you don't really want/need to use a sound server. BTW, I could not find so much info, maybe you can help me to retrieve: - more than just source-code to describe how it works. - the developer's documentation for the appropriate layer to use, etc. - something like: http://wiki.maemo.org/Documentation/Maemo_5_Developer_Guide/Architecture/Mu… ..snip.. now, the pulseaudio cases. First of all, please note I'm not the best advocate for it, btw my 0.05 €. Posting some extracts of your comments to the PA mailing list will definitely give you a better insight for the internals of the server. > Regarding my old nemesis, pulseaudio ( http://tinyurl.com/2976vu6 > == http://old.nabble.com/uninstall-pulseaudio-to-increase-audio-app-stability-… > ), I think the only "elegant" thing about pulseaudio is that it's > bluetooth handling works for those that care about bluetooth; given > the number of bug-reports and incompatibilities pulseaudio generates > in different distros, I'm not sure "elegant" is the right word.... And actually "elegant" was not referred to pulseaudio, but to the way its ports can handle audio routing instead of using ALSA (they bring better synchronisation). Yes, the sound server has shown instabilities in some cases and I personally used to uninstall it on my Ubuntu box immediately after the upgrades. Recently but many improvements have been made at a point that, on a PC, I'm nowadays not seeing it anymore jumping to a steady 30% of the CPU or completely jamming any audio output in the middle of a movie. Another _personal_ feeling I had is that pulseaudio was pretty hard to configure for a generic HW (like distros tend to do), but works pretty well after being tuned for a given one (like 95% of embedded products are). Very often the root issue may have been a wrong configuration for your system. > > From my position, as a multimedia/ALSA/linux-audio developer, having > to go through pulseaudio sounds like an all-around bad idea, and to > have "enforcement" or "compliance" attached makes it sound even > worse. Tell me it ain't so! I can agree from a kernel/ALSA pov (everything in userland appears to be less efficient than any kernel drivers ;) ), I strongly disagree from the system architecture's one. Some points you should consider: - Audio outputs frequency tuning: in the real word a crappy speaker costs less than a good one (strange?) so, unless you've a very high target price, you'll usually have to take the maximum out of garbage by "massaging" the output spectrum in order to get an adequate overall transfer function. And this must work with all of the applications -even the ones coming from third parties on which you don't have the bare minimum control on- and different analog outputs (front, rear, bt, ...). Not that pulseaudio comes with these features out-of-the-box, but it's quite easy to plug them in. - Audio inputs: the dual of audio outputs. - Mixing: it's possible that users will want more than one application accessing the audio output at the same time (e.g. navigator and car radio) or that they'll want to switch bw two different applications all of a sudden (e.g. radio and ringtone). In all these cases they'll want a good mixing and no sudden power steps when the ringtone app does not know about the volume level used for the radio. - Acoustic delay estimation: sitting in the middle of pulseaudio (running as a real-time thread) it's easier to write a proper AEC. Back to 2004 I've tried to grant, with a TI aic31, constant latencies for both LEC and AEC by just using ALSA and the application... It took a really long time to work. - It may not appear so, but it's energy-efficient (see my comments below if you just jumped out of your chair). Now, I don't mean that those things can be handled only by pulseaudio. Actually developers could write their own sound server, or use an already available one, to do all of this, but.. - How long would it take to be better than pulseaudio? (e.g. wrt my points above). - Can it grant the same solid user base and portability across embedded HW? - Could it grant the same level of contribution from companies with solid experience on the subject? - Are there architectural flaws for which pulseaudio couldn't effectively handle these cases? If yes, has anybody tried to discuss about them on the PA mailing list? > > There is a growing class of applications that do not want or need > pulseaudio around -- those using http://jackaudio.org/ . When the > jack audio server launches, the first thing it does it use dbus to > disable pulseaudio. Is that also non compliant? I've no religious issues against jack and actually I don't have that much experience with it, so I'd like to know more about jack on embedded. I'd like to know, for instance, how many embedded, low-power devices are already using it and with which degree of success. Also it would be great to know if anybody has interfaced it with a cellular modem to handle Circuit-switched cellular calls, and if the device has actually been certified for such a service in any countries. > > It seems inappropriate to preclude an entire class of application -- > real-time "pro" audio and video apps that utilize the Jack audio > server to provide low-latency, tightly synchronized audio -- as needed > for modern multimedia creation and playback. Perhaps such applications > are a stretch for an OMAP3-class device, but given the many > audio/media apps listed in http://omappedia.org/wiki/PEAP_Projects , > clearly OMAP4 and beyond might not be, even on a puny "handset." Of > course, those making such audio apps might sidestep pulseaudio > compliance/latency/inefficiency issues by using > http://opensoundcontrol.org/ and an external DAC ( > http://gregsurges.com/tag/dac/ ). > please correct me if I'm wrong, but if I understood well most of the apps using _exclusively_ jack are aimed to audio/video composition/editing. Now, as we are on the IVI ML I think it's quite a strange use case (even though I must admit I don't know which requirements you have). > Finally, it seems odd that in a "handset" environment, pulseaudio is > an absolute requirement. To me, it is just a waste of batteries, see below (and above). > and a > terrible source of unnecessary context switching and interrupts during > audio playback. well, it runs as real-time priority, so it's executed when it's scheduled. Context switches would not be different for any process (e.g. jack) running with the same scheduling. > It's sort of like being forced to drive around in a > gas-guzzling, oversized sport-utility vehicle with 10 foot tires and 5 > feet of ground clearance -- just to drive to the market or work on a > well-paved freeway on a summer's day -- even when one might prefer a > bicycle, motorcycle, sports-car, subway, or whatever tool is best for > the job. funnily, this is EXACTLY the same thing I thought the first time I profiled pulseaudio on the N900, then I found some reasonable explanation (scroll a little below). ..snip.. > Take for example HD audio/video playback -- something where you need a > "sportscar" to get the latency and sample rate associated with the > audio stream while also performing HD decoding (e.g. 16bit/96K audio > is supported on omap3430 per > http://and-developers.com/device_information ). Pulseaudio typically > operates at a fixed rate and forces resampling to that rate, causing > an oft perceptible loss in fidelity. Yes, this is a bad aspect, but it's actually possible to change the output bitrate of the server (it depends on the port used). Maybe you could query on the PA mailing list for more knowledge on the subject. > > IMHO what is needed is not a "digital mixer" and resampler and extra > user-space processing before going into the kernel and out to the > sound hardware via ALSA drivers. We certainly need "use case > management" and the notion of a digital patch bay, and some way of > smoothly mixing between sounds, glitch free switching of sample rates > at the ALSA level, and then choosing the direct path to hardware > that'll best handle the "main audio task" we're doing -- e.g. playing > music, watching a movie, making a phone call, or just using the screen > UI. What isn't needed is "desktop networked audio" capabilities of > pulseaudio, or any extra user-space streaming/mixing/resampling of > signals. so we'll end up writing our own sound server or using a different one, won't we? As an alternative, we may have to heavily modify ALSA to suit our needs, and we'll not have yet covered all of the needed features. > > The inefficiencies introduced by pulseaudio is evidenced by the > n900/meego-1.1 handset, which cannot maintain audio synchronization > during audio or video playback if even the slightest trace of > something else is going on, including a wireless network scan, or even > just cursoring around in a networked terminal (which goes through the > wireless stack in my setup). Personally, I would not say that MultiMedia with MeeGo on the N900 is already at the same quality of Maemo 5. Lots of tuning is imho still missing. > > On Maemo/n900 note what happens when playing back an Mp3 -- pulseaudio > consumes twice the resources at "high priority" of the decoding > process: You must consider that here there many algorithms involved that users/applications don't even know about, like the spectrum optimisations I've been mentioning before. If you could run an oprofile session over your tests you'd see that the actual CPU attributable to PA is pretty lower than your figures. ..snip.. > I'm sure a simple experiment could determine exactly the "effect" of pulseaudio: > > Play the same playlist until the battery wears out using the same > software player outputting first to pulseaudio (pref not through > ALSA's pulseaudio driver because that wouldn't be "fair" to go through > the kernel twice) then play the same through ALSA "dmix" interface, > just to emulate pulseaudio's mixing/resampling functionality. As written above, PA is not only resampling and mixing here.. imho if the user/the developer didn't have to adjust the system to work with PA in order to achieve this, it's a success. The CPU usage comes from the fact we're actually running something we need. > I would > imagine the pure-ALSA solution would pass the "energizer bunny' test > for more hours and far fewer kernel/userspace context switches. Sure it would, but with a lower set of features (and an higher cost for the audio system). It's up to the device price target/customer's pockets and needs to decide what's better. > Although a realtime userspace process like pulseaudio can help deliver > stable audio in a multicore environment -- it may end starving out > other processes on a slower uniprocessor. Which is why I believe a > pulse-audio-free solution should be available and still be "compliant" > on low-end systems. I would agree in some cases, that is when the system conditions don't require it to run multi-application use cases and the price tag for the audio system is irrelevant wrt the audio quality. Note for the reader: if you've reached this point it means you're really interested about pulseaudio on embedded devices :D. Regards > > The one place where pulseaudio is currently helpful is in hooking up > bluetooth devices. But ALSA has it's own bluetooth layer as well, and > other architectures for audio shouldn't be precluded: > http://bluetooth-alsa.sourceforge.net/future.html or Phonon > (http://pulseaudio.org/wiki/KDE ). > > -- Niels > http://nielsmayer.com >

15 years

slaving to jack_start/stop

by Julien Claassen

Hello! If I want to have a simple jack enabled program react to transport control in JACK, what do I have to do? The basics: * the program can start (it will play always from the same point (so no need for relocating, etc.) * the program can stop * I also have an interactive command to make it start. I guess in this case: Just let it start and leave the transport master untouched. Can I easily add the following: When the program is running, due to the interactive start command and external jack_transport play/start comes along, just start over playing? Kind regards and thanks Julien -------- Music was my first love and it will be my last (John Miles) ======== FIND MY WEB-PROJECT AT: ======== http://ltsb.sourceforge.net the Linux TextBased Studio guide ======= AND MY PERSONAL PAGES AT: ======= http://www.juliencoder.de

15 years

[OT] Richard Stallman warns against ChromeOS

by Victor Lazzarini

Stallman hitting the mainstream news: http://www.guardian.co.uk/technology/blog/2010/dec/14/chrome-os-richard-sta… Victor

15 years

Re: [LAD] [Jack-Devel] JACK and RT cgroups

by Dominique Michel

Le Thu, 16 Dec 2010 20:01:46 +0100, Dhaval Giani <dhaval.giani(a)gmail.com> a écrit : > On Thu, Dec 16, 2010 at 7:53 PM, Dominique Michel > <dominique.michel(a)vtxnet.ch> wrote: > > Le Wed, 15 Dec 2010 20:07:37 +0100, > > Dhaval Giani <dhaval.giani(a)gmail.com> a écrit : > > > >> > Turn about again, and i suggest that the jack/RT implications as > >> > part of "being fair to all, with no favourites' weren't given any > >> > consideration, or you wouldn't be here now. > >> > > >> > >> Someone made a noise, and so I knew about it. Not about jack being > >> a favourite. If projectX would have an issue, and I would be > >> informed, I would be equally willing to help them. I however would > >> not be in a position to keep a look at all projects out there and > >> what issues they would face if featureY came into existence. > >> > >> > I'm not throwing a tantrum, just staggered that something like > >> > this could happen in the first place. It just seems so obvious, > >> > as a logical process of feature construction, to consider wider > >> > implications, as you wrote, for all users, including chaps that > >> > use, and/or code for, jack/RT. > >> > > >> > >> Considering the fact that its only JACK facing issues (or at least > >> complaining), that too after two years of a feature being in > >> existence and after about a year for the default cgroup being > >> created, I think the decision was just fine. > > > > I am a non coding project administrator. My distro of choice is > > gentoo, so I am able to configure, compile and install a kernel. > > > > As such, I think than the less you can make is to add a text into > > the kernel help that address the fact that RT_GROUP_SCHED and > > CGROUPS will break any rt enabled software without expropriated > > setup, and that with a pointer to the documentation that will show > > how to do such a setup. > > > > I am still not seeing where RT_GROUP_SCHED and CGROUPS breaks any rt > enabled software. As has been repeated on this thread countless number > of times, there is *no* issue in the kernel. The issue is that by > default the userspace tools create a default group (I still hold to > the view that it is the right thing to do.). What is the point to install a kernel feature without the corresponding user space tools ? So, this is a kernel issue at the first place. And this must be documented into the kernel help. What is the point to install the user tools when its default configuration will break existing applications ? So, the second place to document it is into the user space tools, so that both casual users and distribution makers can make the right choice and configuration. > An application which uses > rt privileges is *special*. From a programmer view, yes. But from the user perspective, this is just an application among other applications. As project administrator, the documentation is one of my major preoccupation. If anyone can understand it, I am happy. If not, I make the needed changes it myself. > Either, > a) The application should make it much easier for the user to use this > capability (by for example creating the appropriate cgroups and so > on), so that it works out of the box or, > b) Inform the user what he needs to do very clearly and have the user > do the hard work. Many rt aware software was existing long ago cgroup and libcgroup. So, b) must be addressed at the first place : the cgroup kernel help (for advanced casual users) and into licgroup documentation. And also, distribution makers must be aware of their choices : by enabling new features that can break existing ones, they must understand that they have a hard work to do : make sure than their packages will work with each other, or they will be loosing users. > > What is being repeated again and again that making a one line change > to a configuration file is going to discourage new users. As I have > mentioned again and again, this has been in there for a few months > now, Most of the good applications cgroup and libcgroup are breaking has been into linux for years. > and if it were such a big deal, there would have been tons of bug > reports. Wrong, users are not fools, and before reporting bugs, they done some searching, or ask to some forum. Why do you thing they will issue bug reports when it is only some good working software that is not working anymore because of a miss-configured third party application ? > Also, this problem is going to come up again once systemd > comes into play. So it has to be fixed by the application as opposed > to people coming about and complaining how Linux developers are > totally against the jack community and are out to get them by making > such changes. Why do you want to force third party applications to adapt their code to your software when it is possible to 1) get ride of your software, 2) configure your software in a why the user can use its favorite application without problem ? Or do you gave a secret agenda where you want to make 1) impossible for every one and 2) impossible for normal users ? > > So, as has been done in the past in this thread, there are folks who > have stepped up to the challenge, and there are patches already > floating about. Instead of encouraging them, and supporting them (with > reviews and the like), instead folks are coming, repeating this > conspiracy theory. In one hand you say that it is easy to configure the user tolls, in the other hand, it is no documentation than a casual user can understand and follow. It is not a conspiration theory but a prod by the act: you are not willing to make your piece of software affordable for the casual user, and it will make life harder for them, as well than for the distribution makers. > > The only way to move forward is for rt applications to be aware that > Linux is different, and if you want your application to work out of > the box, some changes need to be made. I agree with you, but the first change to make are to the documentation of cgroup and its user tools. Again, why do you want to force to make changes to their code when this is not needed. > > This is my last post on non-technical issues in this thread. Do I need a special list ? the LAPA Linux Audio Project Administrator ? Why do you not explain what will be the benefit for a casual linux rt user of cgroup and libcgroup ? If you can do so and I find that it can be useful for the applications I am managing, I can and certainly will change my mind. As project administrator, the project documentation is one of my main concern. If I huge than anyone can understand it, I am happy. If not, I make the needed changes myself. Ciao, Dominique > > Dhaval -- "We have the heroes we deserve."

15 years

Meego pulseaudio "compliance" and "enforcement" (was Re: [Meego-handset] Enabling Speakerphone)

by Niels Mayer

On Tue, Dec 14, 2010 at 1:31 PM, Marco Ballesio > Please check here: > > http://meego.gitorious.org/maemo-multimedia/pulseaudio-policy-enforcement/t… > to get a few more hints on the subject. Hopefully there's more than just source-code to describe the policies and enforcement. Is there a design document stating the "organizational" or "legal" or "human" reasons for said policies and enforcements? And, as a developer, where is the documentation for the appropriate layer to use, the appropriate API, etc -- e.g. for the original question that started this thread -- how to switch on/off speakers, FM-radio transmitter, etc on handset. ( cf my original reply http://lists.meego.com/pipermail/meego-handset/2010-December/000066.html ) Something high-level like the following Maemo document would be very helpful -- but I have been unsuccessful finding such documentation for Meego: http://wiki.maemo.org/Documentation/Maemo_5_Developer_Guide/Architecture/Mu… Also, why not use ALSA use-case-manager: http://opensource.wolfsonmicro.com/node/14 UCM appears to be scheduled for other distros "handset" work: https://wiki.ubuntu.com/Specs/N/ARM/AlsaScenarioManager > the n900 Resource Policy enforcement points were directly interacting > with ALSA. As Krisztian pointed out, it's no more necessary (and at > the limit it may be dangerous for your system's health) to do so > within MeeGo, as the pulseaudio ports can elegantly handle the whole > thing. Potential to blow out my handset speakers duly noted (the n900 goes http://en.wikipedia.org/wiki/Up_to_eleven !), however, I wasn't advocating playing around with the ALSA layer indiscriminately, in fact, I specifically stated: > the "amixer" results of meego indicate an equally complicated > soundchip; where random hacking could render your system somewhat useless... is there documentation on all these values?: > http://nielsmayer.com/meego/n900-card0-amixer.txt . > The only chip mentioned by name is > http://focus.ti.com/lit/ds/symlink/tpa6130a2.pdf "TPA6130A2 Headphone" ................................ Regarding my old nemesis, pulseaudio ( http://tinyurl.com/2976vu6 == http://old.nabble.com/uninstall-pulseaudio-to-increase-audio-app-stability-… ), I think the only "elegant" thing about pulseaudio is that it's bluetooth handling works for those that care about bluetooth; given the number of bug-reports and incompatibilities pulseaudio generates in different distros, I'm not sure "elegant" is the right word.... >From my position, as a multimedia/ALSA/linux-audio developer, having to go through pulseaudio sounds like an all-around bad idea, and to have "enforcement" or "compliance" attached makes it sound even worse. Tell me it ain't so! There is a growing class of applications that do not want or need pulseaudio around -- those using http://jackaudio.org/ . When the jack audio server launches, the first thing it does it use dbus to disable pulseaudio. Is that also non compliant? It seems inappropriate to preclude an entire class of application -- real-time "pro" audio and video apps that utilize the Jack audio server to provide low-latency, tightly synchronized audio -- as needed for modern multimedia creation and playback. Perhaps such applications are a stretch for an OMAP3-class device, but given the many audio/media apps listed in http://omappedia.org/wiki/PEAP_Projects , clearly OMAP4 and beyond might not be, even on a puny "handset." Of course, those making such audio apps might sidestep pulseaudio compliance/latency/inefficiency issues by using http://opensoundcontrol.org/ and an external DAC ( http://gregsurges.com/tag/dac/ ). Finally, it seems odd that in a "handset" environment, pulseaudio is an absolute requirement. To me, it is just a waste of batteries, and a terrible source of unnecessary context switching and interrupts during audio playback. It's sort of like being forced to drive around in a gas-guzzling, oversized sport-utility vehicle with 10 foot tires and 5 feet of ground clearance -- just to drive to the market or work on a well-paved freeway on a summer's day -- even when one might prefer a bicycle, motorcycle, sports-car, subway, or whatever tool is best for the job. Given that's the argument against Java/Android on the handset (it's the SUV of languages/environments) it's unfortunate that lighter-weight and less monolithic and more "unixy" solutions aren't being pursued for audio on the Meego handset. Take for example HD audio/video playback -- something where you need a "sportscar" to get the latency and sample rate associated with the audio stream while also performing HD decoding (e.g. 16bit/96K audio is supported on omap3430 per http://and-developers.com/device_information ). Pulseaudio typically operates at a fixed rate and forces resampling to that rate, causing an oft perceptible loss in fidelity. So in order to allow "digital mixing" for notification signals or phone calls while watching an HD movie, either pulseaudio will be upmixing those signals to 16/96, which is inefficient for audio that doesn't need the higher bitrate; the alternative, which is what we get with pulseaudio, is that the DAC is running at 44 or 48k, and even though we might be listening to material at a higher sample-rate, it'll be resampled and sonic artefacts may be introduced in order to work with the 'lowest common denominator'. IMHO what is needed is not a "digital mixer" and resampler and extra user-space processing before going into the kernel and out to the sound hardware via ALSA drivers. We certainly need "use case management" and the notion of a digital patch bay, and some way of smoothly mixing between sounds, glitch free switching of sample rates at the ALSA level, and then choosing the direct path to hardware that'll best handle the "main audio task" we're doing -- e.g. playing music, watching a movie, making a phone call, or just using the screen UI. What isn't needed is "desktop networked audio" capabilities of pulseaudio, or any extra user-space streaming/mixing/resampling of signals. The inefficiencies introduced by pulseaudio is evidenced by the n900/meego-1.1 handset, which cannot maintain audio synchronization during audio or video playback if even the slightest trace of something else is going on, including a wireless network scan, or even just cursoring around in a networked terminal (which goes through the wireless stack in my setup). On Maemo/n900 note what happens when playing back an Mp3 -- pulseaudio consumes twice the resources at "high priority" of the decoding process: Mem: 239968K used, 5572K free, 0K shrd, 1856K buff, 68204K cached CPU: 31.5% usr 10.3% sys 0.0% nice 53.9% idle 4.1% io 0.0% irq 0.0% softirq Load average: 0.88 0.56 0.27 PID PPID USER STAT RSS %MEM %CPU COMMAND 781 1 pulse S < 3832 1.5 22.0 /usr/bin/pulseaudio --system --high-priority 1317 705 user S < 6320 2.5 12.2 /usr/bin/mafw-dbus-wrapper mafw-gst-renderer 971 1 user S < 1868 0.7 1.3 /usr/bin/dbus-daemon --fork --print-pid 5 --print-address 7 --session On Meego/n900, here's what playing track one in "Music player" looks like -- where even cursoring around on the command-line in bash in the terminal is enough to "desync" the audio stream for a few seconds -- and that's with pulseaudio running at nice=-11 and high priority! Note pulseaudio consumes 31.6% CPU while the decompression, presumably happening in bognor-regis "Media daemon and play queue manager" == 34.5% and finally the media player app itself at 6.7%.... all while consuming 21.3% memory just to play back an MP3.... top - 17:56:15 up 20 min, 1 user, load average: 3.31, 3.12, 2.07 Tasks: 106 total, 2 running, 103 sleeping, 0 stopped, 1 zombie Cpu(s): 18.1%us, 26.6%sy, 17.2%ni, 36.5%id, 1.2%wa, 0.0%hi, 0.3%si, 0.0%st Mem: 226260k total, 215948k used, 10312k free, 84k buffers Swap: 786428k total, 5944k used, 780484k free, 81596k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1063 meego 20 0 127m 9m 7720 S 34.5 4 .5 1:35.09 bognor-regis-da 892 meego 9 -11 191m 4588 3256 S 31.6 2.0 2:45.14 pulseaudio 1104 meego 20 0 2364 960 744 R 10.5 0.4 0:00.22 top 1059 meego 25 5 91628 32m 29m R 6.7 14.8 0:29.26 meegomusic 803 root 20 0 38452 28m 17m S 3.8 12.8 0:38.55 Xorg 876 root 20 0 0 0 0 S 1.9 0.0 0:13.20 ipolldevd Here's *just* watching a video (big buck bunny 240p) on the meego handset -- and no audio is even playing back (constant triggering of desync bug seen when playing back audio stream?) but pulseaudio is working hard anyways, consuming almost 50% of CPU needed to decompress the video and audio stream: top - 17:46:48 up 11 min, 1 user, load average: 4.47, 2.20, 1.03 Tasks: 106 total, 2 running, 103 sleeping, 0 stopped, 1 zombie Cpu(s): 12.8%us, 31.9%sy, 55.2%ni, 0.0%id, 0.0%wa, 0.0%hi, 0.0%si, 0.0%st Mem: 226260k total, 222564k used, 3696k free, 100k buffers Swap: 786428k total, 1224k used, 785204k free, 85424k cached PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND 1007 meego 25 5 269m 41m 32m R 59.3 18.9 1:27.18 meegovideo 892 meego 9 -11 191m 5272 3948 S 26.1 2.3 0:40.00 pulseaudio 803 root 20 0 33092 23m 13m S 4.1 10.6 0:10.83 Xorg I'm sure a simple experiment could determine exactly the "effect" of pulseaudio: Play the same playlist until the battery wears out using the same software player outputting first to pulseaudio (pref not through ALSA's pulseaudio driver because that wouldn't be "fair" to go through the kernel twice) then play the same through ALSA "dmix" interface, just to emulate pulseaudio's mixing/resampling functionality. I would imagine the pure-ALSA solution would pass the "energizer bunny' test for more hours and far fewer kernel/userspace context switches. Although a realtime userspace process like pulseaudio can help deliver stable audio in a multicore environment -- it may end starving out other processes on a slower uniprocessor. Which is why I believe a pulse-audio-free solution should be available and still be "compliant" on low-end systems. The one place where pulseaudio is currently helpful is in hooking up bluetooth devices. But ALSA has it's own bluetooth layer as well, and other architectures for audio shouldn't be precluded: http://bluetooth-alsa.sourceforge.net/future.html or Phonon (http://pulseaudio.org/wiki/KDE ). -- Niels http://nielsmayer.com

15 years

envy24control, resp. it's successor

by Ralf Mardorf

Pardon, I didn't follow the progress of envy24control. Did you finish the recently development and if so, where can we/I get the latest source code? Cheers! Ralf

15 years

Re: [LAD] envy24control, resp. it's successor

by Tim E. Real

(Repost, I replied to our MusE list!) On December 14, 2010 06:47:31 am David Santamauro wrote: > Hi Niels, > > > On Mon, 13 Sep 2010 17:36:11 -0700 > > Niels Mayer <nielsmayer(a)gmail.com> wrote: > > On Mon, Sep 13, 2010 at 2:25 PM, Ralf Mardorf > > > > <ralf.mardorf(a)alice-dsl.net> wrote: > > >Pardon, I didn't follow the progress of envy24control. Did you finish > > > the recently development and if so, where can we/I get the latest > > > source code? > > > > http:// mudita24.googlecode.com > > > > Status: still at 1.03. Waiting for Tim E. Real to commit and then will > > release 1.04. Or use Tim's current patches (see link above). I apologize, haven't had any time to complete the work. I did quietly commit once more later on I think (I hope?), un-announced. Its current state is my current state, there's nothing new to add right now. I was so worried that changing from hard-coded slider min/max and scale markings, to values obtained from asking ALSA, was the right thing to do. I felt it was, to support different, unknown, perhaps yet-to-be-sold cards. We had good discussions on the list about the issues and where it could go from here. Everyone contributed good points and a good understanding of its shortcomings and issues. Neils pointed out there's still some things to take care before we move on like some spacing issues, and of course we must deal with the meters, db markings, and slider height lining up correctly. Fons pointed out his card gives him an extra button below the first slider, for adjustable hardware input level, which kind of ruined the uniform look of the sliders. It works fine as is I think, but yeah, must continue with work on it. > > > > Niels > > http://nielsmayer.com > > ...quick question on the "Monitor PCMs" tab: Why are there 2 sliders > per PCM out? Shouldn't L/R Gang join channels 1 & 2, 3 & 4 etc... > Oh, is the gang not working? It was last I checked. Oh wait, maybe I see what you mean, replace the two sliders with only one, when gang is on? We talked about replacing this with a pan knob or slider, like the Windows version. So many good ideas came out, a good vision of what it could be, but it takes time to implement them. Tim. -------------------------------------------------------

15 years

Introducing ReverbTuner

by Sakari Bergen

Hi All, ReverbTuner is a program that uses AI to tune LV2 reverb parameters to match a convolution reverb. It's a school project made for an AI course, and is a rather quick hack. It's probably the lousiest ever LV2 host, and will crash with some plugins. However, the basic architecture should be rather good :) This has been at a standstill since March, so I thought I'd throw out the code for anyone who is interested. I've designed it to be as modular and scalable as possible, so using other plugin standards or distributing the computational load over a network should not be too hard. Also, the basic concept should work for any LTI effect, not only reverbs. More details (including build instructions) in the paper I wrote for school: http://beatwaves.net/files/software/reverbtuner/paper.pdf To build, you'll need: boost, SLV2, (a git version of) Aubio, Libsndfile, and Gtkmm for the UI the code can be checked out with svn from http://svn.beatwaves.net/svn/reverb_tuner/trunk Br, Sakari

15 years

LV2: Howto

by Harry Van Haaren

Hey all, A while ago I asked about LADSPA plugins, they're implemented & working smoothly now, thanks all that replied & Robin for the code! The next plugin I want to tackle is LV2, I've read lv2plug.in, and I understand how it works. I just don't have a clue where to start with implementing. Does anybody out there have some code lying about that just "bare-bones" loads the plugin? I've read the ZynJackU sources... but to no avail, they're too big for easy learning. Thanks for reading, -Harry

15 years

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Linux-audio-dev