Hi Ricardo :) sorry for my broken English, especially at the moment, because I do have an influenza.
On Thu, 2010-09-30 at 16:18 +0100, Ricardo Lameiro wrote: > Hi Ralf, > > I didn't understood what did you meant with: > > For what do multimedia users (producers, but consumers) need more, > but > > vanilla + rt-patch? Does somebody run a multi-user data server on > the > > same machine, as he is using in his audio or audio-video studio? > This > > would be nonsense. > > What would be nonsense? audio producers using hard RT preemption on > the kernel? > Do you think that a webserver needs more Realtime preemption than > audio work? No, I guess for audio and audio-video productions we only need a vanilla + rt-patch kernel and nothing more. Nobody should run a web-server or anything else on a DAW, so there are no other kernel patches needed. I'm pro PREEMPT RT and against PREEMPT only ;) or any kernel patches that don't make sense for audio, audio-video productions. I was asking for reasons to patch a kernel with something like a 'generic'-patch. A DAW, resp. audio-video-MIDI workstation don't need a special server-kernel, or desktop-kernel etc., just a vanilla kernel + rt-patch. Why does Ubuntu Studio comes without PREEMPT RT, but just PREEMPT?! This is my intension. FWIW, I'm a professional audio and video engineer and did program oldish computers and I'm missing hard real-time for modern PCs. Even the kernel-rt isn't able to do hard real-time, so I don't understand why Ubuntu Studio does prefer a kernel without rt-patch. Today the rt-patch isn't good enough and any kernel without this patch is useless for multimedia production. So a misunderstanding ;)! > > As I see, If a webserver used a RT kernel, it would have a lot of > problems, because it will probably lock in some tasks until they are > finished. > > Audio needs a very low latency, high resolution timer etc, because the > Interrupts given by sound cards and by audio software need to be > addressed as fast as possible, This is what I'm thinking off, I sometimes use the hr timer, that on Linux still is a PITA on some machines and for some apps. Anyway, if possible a multimedia distro should use hr timer (HPET), but always a kernel-rt only. > if they arent, what happens is that the audio buffers, either for the > souncard playback, or capture will run out of data, and then the > continuos steam of audio data will be over, and wait until receive > more info. In a Nutshell, you LOSE audio data, and you will never get > it back, for professional audio that is unacceptable. Also if You give > software RT priorities, it less possible that, for instance, Ardour is > left behind of a twitter client.... unaceptable to... > > I am going to make some simple math with a not so professional cenario > to ilstrate just the data stream, not audo software CPU time. > > > Recording and monitoring out 8 channels (8 in 8 out) at 48KS/s at 24 > bits > > 48000 * 24 = 115200 bps = 14.0625KB/s > > 14.0625 * 16 = 225 KB/s = 1.76MB/s > > Well, 1.76 MB/s is not to much really, well this calc is simple > cenario, provided that the sound card uses real 24 bit audio data > stream, if it used 32 bit, welll do the math. > > Now to a PRO setup.. 192 KS/s @ 24bits > > 192000 * 24 = 4608000 = 0.55 MB/s > > 0.55 * 16 = 8,78 MB/s > > 8.78 MBytes per second, not mbits, FIrewire is rated at 400 MBit per > second... USB in practice is a lot less + Communication overhead. > > This is only on the Audio tranfer side, then you need to send this > streams from each different software, make dsp calculations for > Amplitude (volume) or mixing. This takes time.... so YES a Real time > kernels is better for audio users than for normal users. Specially if > you use Externals Firewire/USB card with high outputs > > note: this are simple calculations made fast, just to demonstrate the > kind of stream we talk about. I assumed 24 bits, this is very rare, > usually it goes with 32 bit, that is a lot more data to transfer. > > If some more explanation on why a RT kernel is prefered for audio, i > can try to answer some more questions, i am not a pro in this tough. > > Ricardo Lameiro > > 2010/9/30 Ralf Mardorf <[email protected]> > > On Thu, 2010-09-30 at 16:38 +0200, Ralf Mardorf wrote: > > On Thu, 2010-09-30 at 07:35 -0400, Ronan Jouchet wrote: > > > Hello everybody, > > > > > > Many are confused about the various realtime kernels, so > here is a > > > reminder of the situation as of Sept. 2010 (but _please_ > see > > > > https://help.ubuntu.com/community/UbuntuStudio/RealTimeKernel , which > is > > > more detailed and continuously updated). > > > > > > ***Summary*** > > > vanilla = unpatched kernel straight from kernel.org > > > generic = vanilla + ubuntu sauce (it's the default ubuntu > kernel) > > > > > > The *soft realtime kernels, prepared by changing > build-time parameters* > > > preempt = generic + mild configuration to reduce > latency > > > lowlatency = generic + aggressive configuration to > reduce latency > > > > > > The *hard realtime kernels, prepared by applying a big > patch* from Ingo > > > Molnar to the kernel source before building: > > > realtime = vanilla + patch (hard to maintain and > stabilize because > > > merging 2 pieces of code is never easy) > > > rt = generic + patch (even harder to maintain and > stabilize because > > > merging 3 pieces of code is harder than 2) > > > > > > ***Availability*** > > > - for Maverick, generic will be the only kernel in the > archives, thus > > > the default kernel for ubuntu and ubuntustudio, but > Alessio has been > > > maintaining a PPA providing lowlatency and realtime > > > - for Natty or later: work is being done to include > lowlatency in the > > > official archives and make it the default ubuntustudio > kernel > > > > > > I hope this clears some doubts. By the way, this confusion > is only going > > > to get more intense at release time (less informed / > technical users). > > > Could we include some kind of note informing users about > this? Why not a > > > "RealTime kernel help" item in the Audio Production menu, > redirecting to > > > the wiki page? > > > > > > Good day, > > > > > > -- Ronan Jouchet > > > > > > > 2 cents, > > Ralf > > > PS: Ok, on 32-bit architecture some might need support for > large RAM in > addition, this might be an additional patch, hat's not needed > on 64-bit > architecture. > > > > -- > Ubuntu-Studio-users mailing list > [email protected] > Modify settings or unsubscribe at: > https://lists.ubuntu.com/mailman/listinfo/ubuntu-studio-users > > > > > -- > Fagote / Contrafagote > Bassoon / Contra-bassoon > http://myspace.com/ricardolameiro -- Ubuntu-Studio-users mailing list [email protected] Modify settings or unsubscribe at: https://lists.ubuntu.com/mailman/listinfo/ubuntu-studio-users
