On Thu, 21 Sep 2006 12:16:25 +0200 Tomas Carnecky <[EMAIL PROTECTED]> wrote:
> Clemens Ladisch wrote: > > Tomas Carnecky wrote: > >> The thing is, in my application I can't set period time to anything else > >> than 21333 and that is, well, kinda bad. > > > > Your application must be able to handle any period size. > > > > Why does the period size matter at all? > > My app can handle that now, but the way how I had to do it defeats the > 'zero-copy' paradigm. > > The situation is this: the application requests a 16kb buffer, at 2 > channels / U16LE this makes a 4096 frames. It's a streaming buffer and > the app writes in the data in chunks of 4096 bytes. I can't map the alsa > mmap'ed buffer to the application (because of the different size) so I > have to create my own temporary buffer and then copy the data to the > mmap'ed buffer. > > tom > > > ------------------------------------------------------------------------- > Take Surveys. Earn Cash. Influence the Future of IT > Join SourceForge.net's Techsay panel and you'll get the chance to share your > opinions on IT & business topics through brief surveys -- and earn cash > http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV > _______________________________________________ > Alsa-user mailing list > Alsa-user@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/alsa-user > I might be wrong, but it seems that 4096 bytes limit comes from these facts: 1) on Linux page size is 4096 bytes; 2) if one allocate more than 4096 bytes, the system cannot guarantee the pages are contiguous; 3) ALSA uses DMA whenever the card supports it; 4) DMA needs contiguous buffer, so we are back to one page 4096 bytes buffer. --Sergei. -- Visit my http://appsfromscratch.berlios.de/ open source project. ------------------------------------------------------------------------- Take Surveys. Earn Cash. Influence the Future of IT Join SourceForge.net's Techsay panel and you'll get the chance to share your opinions on IT & business topics through brief surveys -- and earn cash http://www.techsay.com/default.php?page=join.php&p=sourceforge&CID=DEVDEV _______________________________________________ Alsa-user mailing list Alsa-user@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/alsa-user
