[alsa-devel] question on hardware mixing

[Lee Revell]

On Fri, Dec 5, 2008 at 12:03 PM, Harsha, Priya <priya.harsha at intel.com> wrote:
> Hi,
>
> If my sound card supports hardware mixing, how do I need to code my sound card driver such that I can send multiple streams through ALSA to the sound card driver at the same time?
>

Check out the emu10k1 driver.  You need something like the voice
allocator in that driver that assigns a hardware mixing channel or
channels when ALSA asks the driver for a new PCM stream.

User space would open the same device multiple times (up to the
hardware voice limit) and the driver manages the allocations.  From
userspace POV a hardware mixing device looks just like a single stream
device, but it doesn't return -EBUSY when you open it multiple times.

Lee