At Sun, 06 Jan 2008 11:15:35 +0100, Joachim Foerster wrote: > > Hi Cliff, > > On Wed, 2008-01-02 at 06:26 +0000, cailinhua wrote: > > I want to enable dmix for our sound card.Unfortunately for some reason the sound card driver don't support > > 'mmap' way,it only support 'copy' callback to copy data from upper level to DMA.So ,I think maybe I can modify > > the alsa-lib dmix source code to let it use 'copy' way to send data to the driver. Is it possible？ > > Could you please give me some ideas? > > I don't know how difficult it would be to change alsa-lib's dmix > sources, but my suggestion - in general - would be to alter the driver > of your sound card to use the "intermediate buffer" technique (using > pcm-indirect.h): Setup a buffer in RAM, which can be mmap'ed by > applications and copy the contents of this buffer to the hardware in a > background process for example. > (See Takashi's "Writing an ALSA Driver" guide.) > > I know, perhaps this is not the easiest solution ... and it's not a > "direct" answer to your question - just a thought. Yes, currently it's the only "solution". The dmix requires mmap because the shared mmap among several processes is the key technique of dmix. Takashi _______________________________________________ Alsa-devel mailing list Alsa-devel@xxxxxxxxxxxxxxxx http://mailman.alsa-project.org/mailman/listinfo/alsa-devel
