On Sun, 2011-04-03 at 14:42 -0500, Scott Lavender wrote: > > > On Sat, Apr 2, 2011 at 9:21 PM, Scott Bohon <[email protected]> > wrote: > I am a newbie to Ubuntu and Linux. I upgraded from Ubuntu > 10.10 to > Studio, but I got a message during the upgrade that > essentially said > linux-rt could not be found. Is linux-rt loaded with the audio > package? > Do I need -rt? How do I check if -rt is loaded? If I still > need it, how > do I get it? > > Thank you for your help! > > Scott Bohon > cellist and new techno-musician! > > > > > -- > Ubuntu-Studio-users mailing list > [email protected] > Modify settings or unsubscribe at: > https://lists.ubuntu.com/mailman/listinfo/ubuntu-studio-users > > Hi Scott, > > A lot of the other posts in this thread are pretty intensive and > involved, and since you are a professed "newbie" I thought I would add > some more explanation. > > In this context, the package name "linux-rt" refers to a special type > of kernel, the "real-time" kernel. The "real-time" kernel can help > with recording audio because it affords users to experience more > stable performance at lower latencies (the amount of time from when a > sound is made to when it is heard). > > And keep in mind there are two types of considerations, the "stable > performance" and "lower latencies" in what I mentioned. By "stable > performance" I mean the avoidance of xruns, which are skips or ugly > digital artefacts in recorded audio due to overruns or underruns in > the audio buffer. And "lower latencies" mean that the sound is routed > with due consideration so that the sound made is recorded in a timely > manner. > > Obviously, it doesn't do much good to set the latency extremely low > but have many xruns so that the sound recorded has unwanted noise > introduced in it. Conversely, it doesn't do much good to avoid xruns > but have a latency so high that it appears that you are playing > against your own echo in the Grand Canyon, which throws off timing. > > Again, while the linux-generic kernel provides a moderate amount of > performance, it is expected that the linux-rt kernel can provide a > better performance. But this also considers in other factors such as > your computer and your audio interface. > > Lower powered computers (say a netbook) or a USB2 audio interface > would provide a lower baseline performance in contrast with a > quad-core, 6 gigs of memory desktop machine with an M-Audio Delta 66 > PCI card audio interface. > > It seems to resolve to a matter of compromise which what you have > (hardware) and what you can get (stable performance and latencies). > > It would seem that the -rt kernel is a very important thing. And it > is. Unfortunately it isn't always available. > > The linux kernel, in general, is used by everyone and therefore sees > much attention. In contrast, the real-time kernel (which is made by > applying a patch to the -generic kernel) is only used by a very niche > group and is supported by only a very small group. In times past, the > patch was made and maintained by a single person. I think the group > now consists of three people, but I cannot say how involved each is. > I'm probably wrong on the quantity, though. > > But the result of this is that the real-time patch that is created by > a very small group of people that provides functionality to a niche > group (but very small percentage) of users is not available for every > kernel release. Therefore, we cannot have a real-time kernel for > every kernel version released. Unfortunately, this also means that the > kernel version chosen for Ubuntu (and therefore Ubuntu Studio) may not > align with the available current real-time patch and Ubuntu (and > Ubuntu Studio) will not have a real-time kernel for that release. > > I think this was a consideration, among with others, that caused the > linux-rt kernel to be pulled out of the repositories. Well, this > isn't the most accurate description. The linux-rt package was kept in > the repositories for the extant releases but new linux-rt packages > would not be created for future release of Ubuntu. I think Lucid > (10.04) is the last Ubuntu (and Ubuntu Studio) release that had the > linux-rt package available from the official repositories.
Thank you Scott and all. This is very interesting, if I can find some more time I would like to delve into some of the more technical issues, however, since I am a musician... > > So, having said all that, to answer your questions: > > No the linux-rt package is not loaded with the audio package. it is a > separate package that contains the "real-time" kernel, but is not > available for Ubuntu (or Ubuntu Studio) 10.10 from the official > repository. > > You may need the linux-rt package if you have tried the -generic > kernel, adjusted your settings for jack, and still find that you have > unacceptable performance. Likewise, if you have a firewire device you > may be suffering from irq conflicts and may need the linux-rt kernel > to help you resolve those conflicts. But again, it all matters as to > what hardware you have and what your current performance is. Without > more specifics I doubt anyone can say with certainly whether you need > it or not. But it can help in some cases. > > To check if it is loaded, you can start a terminal and type 'uname -a' > and enter. This will give you a description of your currently running > kernel. This is different than going into synaptic and seeing which > kernels are available on your computer, this will give you the kernel > that is currently running. For example: > scott@lucid-studio:~$ uname -a > Linux lucid-studio 2.6.33-29-realtime #1-Ubuntu SMP PREEMPT RT Wed Aug > 4 17:22:37 UTC 2010 x86_64 GNU/Linux > > I am running the "real-time" kernel currently. > > If you find that you cannot achieve acceptable performance and you > wish to try the real-time kernel on Ubuntu 10.10 or later releases you > will most likely need to use an individual's personal package archive, > colloquially known as a PPA. This are like the official repositories > for software but are "maintained" by individuals. I say maintained > because you neither know the quality of their work nor how well they > keep up with it. I would stick with ones that many people recommend. > I think someone recommended Falktx's PPA, I would recommend his too. > As to the mechanics of PPA's, rather than assume you need this > information and post it, I will wait until you identify that you need > the real-time kernel and also that you need to understand how PPA's > work. > > I hope this expansive email helps you. ...this does really help. So I now need to get my Tascam US-144mkII working!! How do I disable ehci-hcd (USB 2.0)?? Can I do this by port address? (I will start a new thread!) > > If anyone notices where I misspoke or was simply wrong, please do not > hesitate to correct me. I imagine it will help Scott and others > greatly to avoid misinformation. > > ScottL > > -- Ubuntu-Studio-users mailing list [email protected] Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-studio-users
