Linux-audio-user October 2007

linux-audio-user@lists.linuxaudio.org

147 participants
141 discussions

difference between realtime-kernel and low-latency-kernel?

by porl sheean

---------- Forwarded message ---------- From: porl sheean <porl42(a)gmail.com> Date: 16 Oct 2007 12:33 Subject: Re: [LAU] difference between realtime-kernel and low-latency-kernel? To: Fernando Lopez-Lezcano <nando(a)ccrma.stanford.edu> i think a few people have missed what i mean. after re-reading my post i can see it wasn't all that clear. i am still using ubuntustudio, but i downloaded the 64studio *kernel* (not the whole distribution, which i tried but it wasn't quite what i wanted) to replace ubuntu's. after doing that, everything runs perfectly. i assumed that the ubuntu kernel didn't have the rt patches set right, but after downloading a vanilla kernel and patching it myself i noticed that my custom kernel had the same problems as ubuntu's. whilst i am happy to use the 64studio kernel, i am very curious as to what they have done to it to make it work where both the ubuntu-rt and my own custom kernel both have the same symptoms (*very* unstable audio at lower than 40ms latency, and even then ardour often refuses to start plaback - jack drops it off as soon as i press play sometimes on larger projects). i did a diff of the config files from all kernels and couldn't find any notable difference that would explain it (to my limited knowledge anyway), so i assume it is a patch that 64studio has applied in addition to the standard rt patch that is making the difference. are there any other audio performance enhancing patches for the kernel? thanks porl On 16/10/2007, Fernando Lopez-Lezcano <nando(a)ccrma.stanford.edu> wrote: > > On Sun, 2007-10-14 at 12:48 +1000, porl sheean wrote: > > i have actually had no end of trouble with ubuntustudio's (and now > > ubuntu's) rt kernel. on an amd 6000+ system with 1gig ram and a > > rme9652 soundcard i can't get reliable performance under 40 or so ms. > > i even tried a vanilla kernel with the rt patches and had the same > > trouble. the 64studio kernel worked fine, however. i'm currently > > running at 5ms with it and have had no problems. this is even with > > compiz fusion running and spinning the cube whilst playing back audio > > from an 18 channel ardour project. what patches would cause such a > > difference in performance? it isn't any options selected in 'make > > menuconfig' - i loaded the 64studio's ones in and used them. still no > > luck. i can only assume they have added more patches to do with > > realtime performance than just the -rt patchset. > > >From what I gather ubuntustudio does not have an rt patched kernel (ie: > patched with Ingo Molnar's realtime preemption patch). See observations > below: > > > On 05/10/2007, thomas fisher <studio1(a)commspeed.net> wrote: > > I can supply no quantifications for the 32 bit 2.6.20-16-realtime > > kernel in ubuntustudio other than no xruns have been observed. > > So, Ubuntu Studio has a kernel named realtime and they have observed no > xruns (which is not your case, and not the case of other posters). > Obviously it depends on how they test (hardware used, size of buffers, > load on the machine under test, etc, etc) and there's no info on that > post about that. > > > With the low latency kernel, xruns were observed. > > This implies they don't have the low latency patches applied and that, > in their experience, the low latency patch was worse than the mainline > kernel. > > If you have access to that kernel and you can check its build > configuration you could grep for "PREEMPT" there and post the results. > That will definitely tell us which options were used for building it (I > suspect you will find just "PREEMPT_VOLUNTARY" there). > > In my experience, a mainline kernel will lead to xruns at low latencies > (there's always an exception, of course). > > > Jack is the only app that has a -20 priority assigned. > > This implies they are not using SCHED_FIFO for running Jack. Apparently > they are boosting the normal scheduler ring priority of Jack to -20. I > have not experimented with this so I can't comment, except to say that > everyone else (that I know of) is using SCHED_FIFO for running Jack - > SCHED_FIFO is a higher priority scheduling method that can't be > preempted by regular linux tasks, and while it is more risky as a badly > designed application can hang the machine, the tradeoff is of course > much better realtime performance. > > > The general workstation has been running without fault. The general > > Debian / Ubuntu philosophy tends towards system stability. > > The realtime preemption patch is certainly less stable than the mainline > kernel. But if you hardware runs it fine then it is more effective than > mainline for achieving low latencies. > > -- Fernando > > > > Tom > > On Wednesday 03 October 2007 14:54:32 Fernando Lopez-Lezcano > > wrote: > > > On Wed, 2007-10-03 at 18:39 +0200, Frank Barknecht wrote: > > > > Hallo, > > > > > > > > Matthias Schönborn hat gesagt: // Matthias Schönborn > > wrote: > > > > > I've just read that there's a difference between a > > realtime-kernel and > > > > > the low-latency-kernel provided by ubuntustudio. The > > text in the german > > > > > wiki on ubuntuusers.de said, that a realtime-kernel is > > slightly better > > > > > than the lowlatencykernel > > ( http://wiki.ubuntuusers.de/Echtzeitkernel ) - > > > > > then why isn't it used in ubuntustudio? Or do I just mix > > something up? > > > > > > > > I think, this wiki and maybe Ubuntustudio as well are > > using a very > > > > confusing terminology. > > > > > > > > Generally we have two kinds of kernels: The "vanilla" > > kernel as > > > > downloadable on kernel.org and the same kernel, but > > patched with Ingo > > > > Molnars RT-patches. The vanilla kernel, if configured > > properly with > > > > CONFIG_PREEMPT etc., already gives very good performance > > in the low > > > > latency department, enough for many users, even audio > > users. I run one > > > > of these. > > > > > > > > If you want more, then you can install a RT-patched > > kernel, as is > > > > provided in the linux-rt or linux-realtime packages. I > > would call the > > > > Ingo-Molnar-patched kernels Realtime-Kernels or > > Low-Latency-Kernels. > > > > > > To further clarify (or confuse?) the issue, how "low > > latency" the kernel > > > is also depends on how you configure the kernel build > > options before or > > > after patching the kernel with Ingo's patch. For Ingo's > > patch > > > CONFIG_PREEMPT_RT is the best option in terms of latency but > > there are > > > others (CONFIG_PREEMPT_DESKTOP) that have a more > > conservative approach > > > but have (relatively speaking) higher latencies. So from > > worst to best > > > it would be something like: > > > > > > vanilla linuz + CONFIG_PREEMPT_NONE > > > vanilla + CONFIG_PREEMPT_VOLUNTARY (used by the stock > > Fedora kernel) > > > vanilla + Ingo + CONFIG_PREEMPT_DESKTOP > > > vanilla + Ingo + CONFIG_PREEMPT_RT (the one I use for > > Planet CCRMA) > > > > > > (there's more granularity and options in the CONFIG_PREEMPT* > > world but > > > those are the ones that have the biggest impact as far as I > > can > > > remember) > > > > > > -- Fernando > > > > > > > > > _______________________________________________ > > > Linux-audio-user mailing list > > > Linux-audio-user(a)lists.linuxaudio.org > > > > > > http://lists.linuxaudio.org/mailman/listinfo.cgi/linux-audio-user > > > > > > _______________________________________________ > > Linux-audio-user mailing list > > Linux-audio-user(a)lists.linuxaudio.org > > > http://lists.linuxaudio.org/mailman/listinfo.cgi/linux-audio-user > > > > _______________________________________________ > > Linux-audio-user mailing list > > Linux-audio-user(a)lists.linuxaudio.org > > http://lists.linuxaudio.org/mailman/listinfo/linux-audio-user > >

18 years, 1 month

Musix GNU+Linux upgrade without reinstall

by Marcos Guglielmetti

Hi! Well, we did it, but it's in a beta stage. Now you can upgrade from Musix 0.99, 1.0 RC1, R1 or R2 to R3 (cd version, not DVD) without even the new Live-CD 1.0 R3 Test1. Just open a Terminal and type: sudo apt-get update sudo apt-get install musix1.0r3-upgrade (Note: you must use sudo if you want to upgrade your personal Desktop files... dont do it as a "simple" root user) New: * Linux 2.6.23-rt1 * Ardour 2.1 * Musix Control 1.4.1 * Canorus 0.3.1 * jackd 0.103.0 * horgand 1.12 * xfe 1.04 and many more... Some bugs were corrected, so, it's clever to upgrade :) Regards, -- MGG

18 years, 1 month

RealTime Kernel for openSUSE 10.3 x86_64

by David Haggett

<sigh> My last message to the list was asking for help getting a real-time kernel for openSUSE 10.2. Sadly it was never resolved - there are kernel-rt packages available for 10.2, but they were out of step with the kernel-source package. I've now migrated to 10.3, because I was aware that an RT kernel was being developed for it. Sadly, when I got to the RT kernel I noticed that the package in the main repository was still at the original shipped kernel version (2.6.22.5-31). The default kernel and kernel source packages have both moved on to 2.6.22.9-0.4 - so if I install the RT kernel, I will not be able to install the NVidia driver for it. I am now trying to downgrade the kernel and sources to the original shipped version so I can try the RT version. Does anyone have any advice that might help? -- David Haggett

18 years, 1 month

Card for bit perfect SPDIF throughput

by Mark Constable

Can anyone suggest a couple of ALSA-safe cards that will provide "bit perfect" SPDIF throughput ? In other words, if I play back a 44.1khtz CD that the card will not resample the signal, at all, on the way through to the SPDIF output. And, in the case of a nVidia MCP67 (hda_intel), which seems like it does 96k and 192k, is there some way I can determine how well, or not, it passes through any digital signal? --markc

18 years, 1 month

nted is very nice

by Ken Restivo

-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Thanks for pointing me to nted. It looks *very* useful. Simple, clean, easy to learn, and lots of keyboard shortcuts. But the most amazing thing about it is: it doesn't try to produce its own sound or have any sound engine of its own! This is, I think, its most brilliant feature. No soundfonts, no sound drivers, nothing. All it does is access the ALSA sequencer and send MIDI to my JACK softsynths. So I can note something out and hear it with my own synths. Some bandmates and I were just lamenting how paper and pencil is so much easier to deal with than most notation software out there. Maybe not. nted looks like it might even be easier than paper and pencil. - -ken -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.6 (GNU/Linux) iD8DBQFHFbgDe8HF+6xeOIcRAsa6AJ992FQ3WixbeuepaZTeliIdSiiJagCgqKYF NOcvepQVRZbCrXkeRh3yXm4= =TBUb -----END PGP SIGNATURE-----

18 years, 1 month

Sound Editors, Alsa, and alsa.conf troubles

by Tobiah

I have a soundblaster as card0 and a Delta44 as card1. I want to keep it this way so that most trivial sounds come through the soundblaster, and leave the Delta44 open for use as a serious soundcard. Lately, I've been having trouble getting any decent sound editor to use the second card. Audacity should do it, but on my Kubuntu system, it crashes when opening or playing a file. I find this in my log: alsactl: resmgr: communication failure: Connection refused or audacity: resmgr: communication failure: No such file or directory So, unless I can get it to work, I'm stuck with other editors. It's amazing, but many of the decent looking editors will not allow any configuration of device, and always use /dev/dsp0. That sucks. Now, when they do allow me to select the second card as /dev/dsp1, I get errors about the format not being supported. This is because the Delta is really a 12 channel card without hardware for the extra channels. In properly written alsa programs, I can use hw:plughw1,0. But I haven't found any decent editor that will let me specify something like this. Now I'm wondering whether I can do something tricky in my /etc/asound.conf that would let the unaware programs use my Delta44. I look at the docs (such as they are) once in a while, but I never come up with anything valuable. Just today, I started by making a simple slave: pcm.delta { type hw card 1 device 0 } pcm_slave.sltest { pcm delta } pcm.live { type hw card 0 device 0 } But aplay will not use -D sltest: ALSA lib pcm.c:2090:(snd_pcm_open_noupdate) Unknown PCM sltest aplay: main:547: audio open error: No such file or directory I don't know how to go about getting a better understanding of this most arcane config file. Thanks, Tobiah

18 years, 1 month

Re: [LAU] pam and jack

by arisstotle.54695488＠bloglines.com

--- joq(a)io.com wrote: On 17 Oct 2007 01:58:08 -0000, arisstotle.54695488(a)bloglines.com > <arisstotle.54695488(a)bloglines.com> wrote: > > This is most strange to me. Weeks ago, I configured pam to allow the audio > > group to operate high priority real time precesses. I could start jackd and > > it would run as priority 80, for example. However recently Ardour constantly > > disconnects from jack, and look at the output of top, jack seems to only be > > runing at the default priority of 20, regardless of the settings I pass on > > the command line. thoughts? > > > What command line do you use? > -- > joq > $:jackd -R -P 80 -d alsa -p 64

18 years, 1 month

pam and jack

by arisstotle.54695488＠bloglines.com

This is most strange to me. Weeks ago, I configured pam to allow the audio group to operate high priority real time precesses. I could start jackd and it would run as priority 80, for example. However recently Ardour constantly disconnects from jack, and look at the output of top, jack seems to only be runing at the default priority of 20, regardless of the settings I pass on the command line. thoughts?

18 years, 1 month

GNU Denemo chokes a dual core 2 GB server

by Christian Einfeldt

hi My question is fairly long to explain, but simple to summarize: why are we experiencing delays in playing music compositions using GNU Denemo under Edubuntu over a GB network that should be performing better, and what can we do to solve the problem without spending any money? I am a volunteer supporting a public middle school with FOSS. We have a brand new dual core server with 2 GB of RAM whose only purpose in life is to support 24 chubby clients running edubuntu. The thin clients have at least 256 MB of RAM, and most of them have swap space on their hard drive also, although some of them are true thin clients in that the hd has no swap and is basically a vestige. I am told that we have a gigabyte network. The server feeds the signal to the first 18 clients through one GB switch, and then that switch feeds another identical switch with services about 6 more clients. Our problem is that when we use GNU Denemo to play the short little compositions that the students write in class, we can have only one student play his / her composition at a time or the system is choked, meaning that it lags. More specifically, all of the students find that their GNOME desktops are almost completely non-responsive to the mouse. The mouse still moves, but programs launch very slowly for about 5 mins, at which time the choke point is presumably cleared, and then one student can again play his / her composition. It might be possible for, say, 2 students or maybe even three students to play their music; but we don't know where that stress point is. And, in some ways, it doesn't even make sense to slowly add students and have them play music, simply because some people who have heard of this problem in passing furrow their brow and say that we shouldn't be having these problems. We are, of course, going to be trying to get more RAM in the clients; and swap for all of the clients; and we have thought of running GNU Denomo natively on each of the clients by booting them as stand alone work stations. But I am a volunteer, and this inner city school has absolutely no budget for a real tech support person, and all of the teachers already are at work by 6:50 a.m., and they usually stay until 6:30 p.m., and then each of the teachers is expected to be available to field phone calls at home until 8 p.m. All of this might sound kind of drastic, but our students typically come to this school of 290 students under-performing their grade level by 2 grade levels, but leave the school as 8th graders typically performing at or above grade level. Seventy-five (75%) of our students come from households below the federal poverty guidelines. 65% of our students are African American; 17% are Latino; 10% are Asian; and 8% are Caucasian. Despite the life challenges facing our students, last year our students tested in first place (as a student body) based on standardized testing. So this school is succeeding in many ways, but they are really struggling in terms of technology, and that is all because of funding shortfalls. Coincidentally, the students spend no time here on Windows boxes, except for occasionally random Internet browsing on a teacher's Windows box. But that is the exception, because, as you can imagine, the teachers don't want the students accessing their computers. So when the students are not in the lab, they are using PClinuxOS boxes in several of the classrooms to do their Internet research. Overall, this school is making miracles with no funding. I am hoping to move the whole school to FOSS eventually, but of course there is still a lot of work to be done. Thus far, the music teacher is fairly impressed with the ability of students to compose music on GNU Denemo, but she would just like to be able to have all of the students listen to their compositions at the same time. Typically, these compositions are no more than, say, 6 or 10 bars long, just enough to get the students familiar with the basics of scales, rests, note duration, tempo, beat, etc. Just the basics. Thanks in advance for the help. -- Christian Einfeldt, Producer, The Digital Tipping Point<http://archive.org/details/digitaltippingpoint>

18 years, 1 month

leadsheet software needed

by Josh Lawrence

Hello all! I group I recently joined is doing a gig in two weeks. After a few months of practicing, there are still a few tunes that I don't have memorized, so I need to generate a lead sheet pretty quickly. I could write them out by hand fairly easily, but I would like to keep a digital library of leadsheets. Is there a program that will generate "realbook-style" leadsheets for Linux? I basically need just a simple staff with what I call rhythm slashes, and a mechanism for putting chord symbols above the staff. (Jazz players who have spent many nights in a dark room reading the original - and illegal - Real Book know exactly what I'm looking for here.) I realize there are complex tools like Lilypond that will probably do this, but I would like something simpler, maybe with a gui. Thanks! -- Josh Lawrence http://www.hardbop200.com

18 years, 1 month

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Linux-audio-user October 2007