This looks Great ! I haven't yet experimented a lot with .asoundrc files, so please excuse me if the following questions are irrelevant or OTO, but:
I was wondering if one could define a plug pcm, that offers two stereo pairs routed with policy "average" to a single-stereo "hw" slave. My understanding is that until this dmix pcm, there was no "official" means supported by alsalib to achieve software mix of streams comming from differents apps. Could I have one app open the first pair of my hypothetic plug pcm, and another app open the second pair ? I guess this would be managed like a concurrent access to a pcm, and block or fail the second open() call. Would'nt it be nice to create a dmix pcm "behind" a such plug pcm, to provide mix in a transparent way ? thanks for your light over this Marc. > -----Original Message----- > From: Jaroslav Kysela [mailto:[EMAIL PROTECTED]] > Sent: mercredi 12 février 2003 10:46 > To: ALSA development > Subject: [Alsa-devel] dmix plugin > > > Hi all, > > a next step to get the lowlatency sharing of exclusive > PCM devices > is in ALSA CVS - the dmix (direct mixing) plugin.. > How it works? Basically, the playback in driver runs forewer > without any xrun detection. The ring buffer (only just played > areas) is > also silenced in each interrupt. Then we have multiple clients and a > process (server) which passes the file descriptor of playback > devices to > them. The server also takes care about freeing of used shm memory and > semaphore. > The big step forward is that we share one mmaped ring buffer > accross many processes and each process can add samples into > it without > any process<->kernel swaps. Also, each processes are independant, thus > failing of one doesn't break others. It's not multithreaded, > we don't need > this mechanism. > > Here is an .asoundrc example configuration (plugin defaults > are 48kHz, > stereo, signed 16-bit little endian): > > pcm.dmix { > type dmix > ipc_key 1234 # must be unique for all dmix plugins!!!! > slave { > pcm "hw:0,0" > } > } > > Then try: 'aplay -Dplug:dmix <filename>' on multiple consoles. > > Note that it's still alpha code and there are some not correctly > implemented functions (like drain, rewind and more). Note > that you'll need > also the latest ALSA driver from CVS, because the silence settings was > enhanced a bit and bug in the timer code will crash your machine. > > Enjoy it! > Jaroslav > > ----- > Jaroslav Kysela <[EMAIL PROTECTED]> > Linux Kernel Sound Maintainer > ALSA Project, SuSE Labs > > > > ------------------------------------------------------- > This SF.NET email is sponsored by: > SourceForge Enterprise Edition + IBM + LinuxWorld = Something 2 See! > http://www.vasoftware.com > _______________________________________________ > Alsa-devel mailing list > [EMAIL PROTECTED] > https://lists.sourceforge.net/lists/listinfo/alsa-devel > ------------------------------------------------------- This SF.NET email is sponsored by: SourceForge Enterprise Edition + IBM + LinuxWorld = Something 2 See! http://www.vasoftware.com _______________________________________________ Alsa-devel mailing list [EMAIL PROTECTED] https://lists.sourceforge.net/lists/listinfo/alsa-devel
