Linux-audio-dev September 2003

linux-audio-dev@lists.linuxaudio.org

94 participants
75 discussions

Re: [linux-audio-dev] KEYBOARDS: Linux is not suited for audio applications ...

by Stefan Nitschke

> >Hello, > >the german magazine KEYBOARDS has answered a readers question about audio >and linux with tremendous ignorance. I think this is a good chance to push >linux to the attention of "the masses". > >Here is the full text of question and answer (first in german, so anyone >can correct my errors ;-). > >... snip well the answer from the guy is in my opinion correct atleast for now. You need a LL-patch to get audio work as desired and AFAIK there is no … [View More]

21 years, 6 months

Re: [linux-audio-dev] Wrote a real time safe memory allocator in C++

by Benno Senoner

Greg Reddin wrote: > Is there a web resource or book or something where one can learn > about these programming caveats for audio developers? I knew nothing > of this problem, but it makes sense when you mention it. I don't think that there is an all-in-one howto around, most infos are scattered around the net (and most issues can be solved with a bit of knowledge of the real time paradigm and a bit of common sense) > > > Or do I just have to do this for a few years and … [View More]learn the hard way? > :-) Most developers seems to do so, they are just too lazy to think about the constraints that real time programming imposes. They believe they can make full use of the operating system, call any system calls they like, C++ constructors, malloc()s etc, accesss to mutexes locked by low priority GUI threads and then after wonder why their application does not work with low latencies or why there are sporadic dropouts they cannot get rid of. most problems go away if you increase the buffer sizes (thus latency) to let's say 20-50 msec, but as we know any soft-instrument with bigger than 15-20msec latencies becomes unplayable (measured by professional standards). Anyway there are not many rules to follow: run the audio thread SCHED_FIFO (and do not use SCHED_FIFO on other threads, except when you know exactly what you are doing). in the audio thread just do not call any system calls except read/write to the audio device . especially file system ops memory allocation, calling C++ constructors/destructors (cause memory allocation/deallocation) etc. Basically any operation that could possibly be blocked because it has to wait for some event, data, etc. Do all communication between audio thread and other threads via lock free FIFOs or shared mem. Avoid mutexes like they were radioactive material. (there are a few execptions where they are allowed like using mutexes between two real time threads where you know that they will not tie up the CPU for more than a certain amount of time, or using pthread_mudex_trylock() in the audio thread that tries to acquire the mutex but if it fails it returns immediately without stalling). For example Ardour is well designed in this regard, and this is why Paul is an experianced programmer (and probably learned some RT issues the hard way too). Unfortunately many audio apps on linux do not meet "low latency standards" or better are not designed with real time safeness in mind and I think it is one of the obstacles that keep them out of the professional domain making them look like a toy. It is sad because there are many nice apps with an excellent sound generation engine, but often the framework around that engine is weak. It does not that actually that much energy to fix it but people seem either too lazy to do that or either do not know what the RT-safeness guidelines are. I never understood it ... it is much more complex to desing a synthesis algorithm, etc than just avoiding a few mutexes and use a lockfree-fifo instead etc. Anyway I agree it would be cool to have page on the LAD site that explain all these issues and provide source for some basic routines and classes. This would prevent that the mistakes are made all over again. cheers, Benno http://linuxsampler.sourceforge.net ------------------------------------------------- This mail sent through http://www.gardena.net [View Less]

21 years, 6 months

[linux-audio-dev] [german] Keyboards Leserbrief zum Thema Linux und Audio

by Uwe Koloska

Hallo, hat jemand von euch in der aktuellen Keyboards die Antwort von Herrn Hain auf die Leseranfrage zu Linux und Audio gelesen? Die strotzt ja nur so von Unwissen, das schier danach schreit eines besseren belehrt zu werden. Vielleicht könnten wir ja gemeinsam eine Antwort erarbeiten. Bei Interesse könnte ich heute abend auch den Text von Frage und Antwort hier posten (leider gibt's die Leserbriefe nicht auf der Keyboards Webseite). So long Uwe -- voiceINTERconnect www.… [View More]

21 years, 7 months

Re: [linux-audio-dev] Pair of Audiophile 24/96s?

by jeff wade

I too have a pair of Midiman 24/96's, and they sound great. I've been toying with .asoundrc (I've read the RME Hammerfall config and the TwoCardsAsOne page too), and so far I dont have what I want. I looking for both cards to function in sync, as a four (or eight?) - track recording platform. Can someone point me in the right direction with my .asoundrc file, and jackd options? how do i ensure the cards are synched?

21 years, 7 months

[linux-audio-dev] CONFIDENCIAL REQUEST

by johnny.mboma1＠caramail.com

Dear Sir, I need your help,I am John Mboma the son of a Late minister during the reign of mobutu seseko, I came to know you in the course of my search for a reliable and God fearing partner and I decide to contact you because I believe you are a reputable person and I felt you can help us over this confidential matter. I count on your intergrity and honesty to be able to handle this business. My father was a minister in Democratic Republic of Congo during the reign of … [View More]

21 years, 7 months

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Linux-audio-dev September 2003