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From: Gerd Hoffmann <kraxel@redhat.com>
Date: Thu, 04 Sep 2014 10:00:57 +0200
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Subject: Re: [Qemu-devel] Audio stream handling in QEMU device model
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To: Harry Cruise <princeharry_89@yahoo.com>
Cc: "av1474@comtv.ru" <av1474@comtv.ru>, Qemu-devel <qemu-devel@nongnu.org>

On Do, 2014-09-04 at 00:22 -0700, Harry Cruise wrote:
> Hello,
> 
> 
> I am trying to comprehend QEMU AUDIO backend functionality and need to
> implementing device which has few audio channels from which it
> receives audio streams (sampled at some specific frequency), and
> further process that data stream like mixing two stream.
> 
> 
> I am new for the QEMU, Please help me in following queries:
> 
> 
> 1) Please suggest some document and example/device implement which has
> use qemu audio backend.

hw/usb/dev-audio.c (implementing usb speaker emulation) is probably the
best sample code for that.

> 3) What steps I need to add into device to setup audio support as per
> the requirement I mentioned above ?

You can just create multiple streams.  AUD_open_* returns a handle so
you can disturgist them.

> 4) what is the basic working flow of audio backend and accessing audio
> streams using dma ?

Nothing special for audio here, they do dma like any other device.  You
don't see that in hw/usb/dev-audio.c though as DMA is handled elsewhere
(uhci/ehci/xhci usb host adapter emulation).  You might want to look at
intel-hda for pci dma sample code.

HTH,
  Gerd