>Is it possible to have both stream pointers working on the same physical >buffer? A slightly delayed start of playback should then give a nice IO >latency. Are there any other approaches viable? Ideally i'd like to get this >working while not depending on userspace scheduling heavily.
you have to depend on userspace scheduling unless you write a kernel module. >Any suggestions/constraints about the following ideas? >1. traditional blocking read/write in seperate threads >2. traditional non-blocking read/write in a single thread >3. asynchronous SIG_IO triggered read/write handling >4. mmap'ed buffer for read+write the JACK code for its alsa_driver shows the way to get the lowest latency and greatest efficiency that i know of without playing "dirty" tricks. it uses mmap access, and sleeps using poll(2) to wait for the audio interface to be ready. read/write access would not change the latency, it would be just a little less efficient for large numbers of channels. the code is rather complex, however. there is a simpler example in my ALSA primer which has links on the ALSA programmers documenation page at www.alsa-project.org. personally, i'd just fire up JACK and use a slight, tiny modification to the jack_simple_client example to do this. you hardly have to write any code then. --p ------------------------------------------------------- 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
