[alsa-devel] question on hardware mixing

Lee Revell rlrevell at joe-job.com
Sat Dec 6 05:58:32 CET 2008

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.


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