Linux-audio-dev

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4 participants
7538 discussions

[linux-audio-dev] How to access "real-time" capabilities

by Ian

Hi, I have been lurking on the list so now I want to say hi.I am part of the ubuntu users group in Brazil. Can anyone tell me *very briefly* what is the current state of play regarding realtime-lsm in the 2.6.* kernels and whether this feature (or something like it ) is likely to be introduced into the kernel anytime soon. I cannot find anything on the net apart from some discussions between the kernel devs and linux-audio-dev guys which did not really clear anything up for me. I am not asking in order to cause a big debate about the values or otherwise of realtime-lsm but I want to make sure I am clear about the current situation. We have made some metapackages based on DeMuDi for the Ubuntu-BR Multimedia-audio distro and doing something like this -> # apt-get install build-essential fakeroot linux-headers-$(uname -r) is the only way I can think of to enable realtime-lsm in the kernel without asking the user to use module-assistant to enable it after install which is something we don want to do Regards Ian Linux is more than a business. Linux is a community. Linux is more than an operating system. Linux is a dream. We know that as computer users, we represent a small percentage of the computer industry as a whole. The important thing is that we know we're right, and we're going to change the future of the software industry one long night at a time.

20 years, 8 months

[linux-audio-dev] Looking for fast integer resampling code

by Dave Chapman

Hi, I'm working on the Rockbox - http://www.rockbox.org - project, which is a project to develop an open source (GPL'd) replacement firmware for portable digital audio p[ayers. Rockbox has been running on various Archos MP3 players for about 3 years. The latest hardware that Rockbox is in the process of being ported to is the iRiver H120/H140 players. These consist of a 120MHz Coldfire (m68k-based) processor and 32MB of RAM. There is no floating-point support in the Coldfire. We currently have real-time playback of MPEG audio (via libmad), Ogg Vorbis (via libOgg), FLAC (via libFLAC), A52/AC3 (via liba52) and (of course) WAV files. Unfortunately, the audio hardware only supports a 44.1KHz samplerate - meaning that we have to resample other frequencies. The most common case will be downsampling 48KHz->44.1KHz, but there are also users who need upsampling from various lower frequencies (e.g. for use with audio books). So we're looking for pointers to any high quality (but fast!) resampling code that could be used. Thanks in advance, Dave.

20 years, 8 months

[linux-audio-dev] disaster update

by Dave Phillips

Greetings: I ran memtest for a day, the RAM's fine, so I brought in another machine, added my drives, memory, and cards, everything's working all right. Once again I learned a lot, thanks to everyone who replied. But I gotta get me some new iron... Best, dp

20 years, 8 months

[linux-audio-dev] [Slightly OT] How to access "real-time" capabilities

by asbjs＠stud.ntnu.no

This is, I know, slightly off-topic for this group, as it does not deal with audio per se. It does, however, deal with the "real-time"/preemptible Linux kernel, for which I think most of the expertice is gathered here. The OS is Linux, the computer an ordinary PC. The task we are faced with is to run a program, tcpreplay, in such a way that it delivers its network packets as precisely as possible. I.e. the packets should be delivered to the network with the smallest possible timing error. We think that the way to minimize this timing error is to use a kernel with the real-time patches, as this will improve latency and response times. The question is how we can assure that the program really utilizes the real-time capabilities of the kernel. My understanding is that having a real-time capable kernel is only the first step, the second necessary step is to get access to this capabilities? So, how does one accomplish this, given that the program itself does nothing to achieve this? * Will an ordinary program, run as root, take advantage of the real time capabilities of the kernel? * Will an ordinary program, run as a user that is a member of the "audio" group on f.i. Agnula, take advantage of the real-time capabilities? * If given a real-time kernel, what else is necessary to take advantage of its capabilities? * How does normal priorities (nice, renice) play together with the real-time kernel? With kind regards Asbjørn Sæbø

20 years, 8 months

[linux-audio-dev] sample browsing app

by mimo

After my initial problems with jack I must say I have come to like jack. Especially together with muse. Now I wonder, is there something like a sample browser (possibly with jack output) that allows traversing through directories and click-n-play audio files in them? Something like good old fastwav on windows... I have searched and searched but everything I could find needs at least two clicks to play.. also kde/qt drag and drop would be nice.. thanks, mm

20 years, 8 months

Re: [linux-audio-dev] [ot] [rant] gcc, you let me down one time toomany

by eviltwin69＠cableone.net

On Thu, 9 Jun 2005 10:05 , 'Chris Cannam' <chris.cannam(a)ferventsoftware.com> sent: >N Smethurst: >> Since a vector is a wrapped C array (i.e. contigous), the [] operator >> compiles to the C equivalent when optimisation is turned on. > >I was thinking of iterator operations, having vaguely recalled that the vector iterator in the gcc library had at some point changed from an actual pointer to a wrapper class. Looking at the code, though, the wrapper is so thin that it probably isn't an issue with optimization on. > > I was under the impression that there was bounds checking going on with vectors. Is this not the case? Jan

20 years, 8 months

[linux-audio-dev] [ot] [rant] gcc, you let me down one time too many

by Tim Goetze

Frailty, thy name is GCC A Modern Drama in Three Scenes. Dramatis Personae: An ardent programmer and a popular C++ compiler -*- Prologue: Appalled by the rat race commonly known as the proprietary software business, our young and gifted hero joins the light side, deeply inspired by the manifold yet subtle qualities of free software. Scene I: Our hero in day-and-night-long sessions optimizes the hell out of a SSE2-based n*4-band IIR equalizer. Of course in assembly, and mixed with C++ templating. The final code is about 10% faster than floats on AMD, probably a fair bit quicker yet on P4 systems. Enter gcc version 3, which drops multi-line inline assembly support. Said assembly code becomes effectively unusable and dies a quick and unsung death. Scene II: Our hero puts years of work into an all-round realtime audio and MIDI library that expands the Python programming language. While having its flaws, it's a versatile, surprisingly stable and immensely capable system, partly thanks to a very clever (according to our hero) design that subclasses Python's C types in C++. Enter gcc version 3, moving the vtable member to memory offset 0 of a derived type even if the base type is in C which doesn't know about vtables. As a result, the very foundation of said library's type system is rendered nonfunctional since Python expects its type header to reside in the very same memory location. With no precautions for such an abrupt change taken and the implications requiring a manual review and substantial rewrite of a good 50.000 lines of source code, said library dies a slow and painful but equally unsung death. Scene III: Our hero bundles his DSP efforts into a free plugin library, once again saving himself much work and improving code readability by using C++ templates, resulting in quite an elegant object system and source code, hethinks. Enter gcc version 4, which requires the templated types' constructor code be rewritten in the most nonsensical, misleading and ugly fashion possibly imaginable this side of Hungary and Redmond, WA, according to our (now not so very young anymore) hero. Epilogue: Our hero has completely and permanently lost his faith in the popular compiler. Disillusioned and indecisive, he resigns himself to henceforth reluctantly write C++ only to support his miserable life. His plight is so bad he downright refuses to support the latest follies of the popular compiler in his free software efforts. -*- Will this be the end? To be continued, hopefully. Cheers, Tim

20 years, 8 months

Re: [linux-audio-dev] [ot] [rant] gcc, you let me down one time toomany

by eviltwin69＠cableone.net

On Thu, 9 Jun 2005 23:41 , David Cournapeau <cournape(a)gmail.com> sent: >On 6/9/05, stefan kersten steve(a)k-hornz.de> wrote: >> On Thu, Jun 09, 2005 at 10:31:35PM +0900, David Cournapeau wrote: >> > _Z6vectorSt6vectorIiSaIiEE: >> > .LFB539: >> > .L2: >> > .L7: >> > pushl %ebp >> > .LCFI0: >> > movl %esp, %ebp >> > .LCFI1: >> > popl %ebp >> > ret >> > >Well, that's what happens when one post some code after some heavy >coding all day long, and when one tries to answer two questions at the >same time....That's why I would have prefered to find the relevant >part instead in the C++FAQ :) > > Anyway, for the question "is there bound checking with operator[]", >the answer of Bjarne Stroustrup is no :). > The other problem "is [] as efficient for vector and plain c array >?", well, people who know better than me asm/gcc can test and answer. > Yeah, it really needs to be tested to tell. I remember taking a course in VAX Macro asm back in the days of dinosaur eggs and phonograph needles. The book, DEC, and the teacher all said you could turn off the VAX debugging mode when you compiled. I wrote some self-modifying code for one of the exercises (I wouldn't do that in real life ;-) The compiler still slapped in some debugging stuff and it wouldn't work. It was a real simple program though so the instructor checked it and passed it anyway ;-) Jan

20 years, 8 months

Re: [linux-audio-dev] [ot] [rant] gcc, you let me down one time toomany

by Chris Cannam

Jan Depner: > I was under the impression that there was bounds checking going on with > vectors. Is this not the case? Nope. Chris

20 years, 8 months

Re: [linux-audio-dev] [ot] [rant] gcc, you let me down one time toomany

by Chris Cannam

N Smethurst: > Since a vector is a wrapped C array (i.e. contigous), the [] operator > compiles to the C equivalent when optimisation is turned on. I was thinking of iterator operations, having vaguely recalled that the vector iterator in the gcc library had at some point changed from an actual pointer to a wrapper class. Looking at the code, though, the wrapper is so thin that it probably isn't an issue with optimization on. Chris

20 years, 8 months

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Linux-audio-dev