(Please don't remove the list from CC. Re-added.) On 03/20/2013 11:21 AM, Thomas Martitz wrote: > Am 20.03.2013 10:06, schrieb David Henningsson: >> Sure. You said "pa_simple_read/write() is expected to be done from the >> main thread", but you meant more like "pa_simple_read/write() is >> expected to be done from any other thread than the callback context"? >> >> A pa_simple callback API, if implemented, I would envision would >> supply a data pointer and length, and ask for the callback function to >> either read that out (record) or fill it in (playback), and to do so >> without calling into the PulseAudio API at all. > > Or return a pointer (which is expected to point to a buffer of bytes > length) in the playback case, to enable zero-copy? The pointer sent to the callback function would be in SHM, shared memory between client and server, which is allocated by PulseAudio. That's the way to achieve zero-copy. In the callback function you would generate your audio data straight into this buffer. (Or one-copy, really, because there is a later copy from the shared memory into the DMA buffers of the sound card, which is done inside the PulseAudio daemon process.) -- David Henningsson, Canonical Ltd. https://launchpad.net/~diwic
