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From: "Kővágó, Zoltán" <dirty.ice.hu@gmail.com>
To: qemu-devel@nongnu.org
Cc: Gerd Hoffmann <kraxel@redhat.com>, Markus Armbruster <armbru@redhat.com>
Subject: [Qemu-devel] [PATCH 16/25] audio: add mixeng option (documentation)
Date: Sun, 25 Aug 2019 20:46:18 +0200
Message-ID: <76a0c0fda2f78cfb5f2234aa7e28073aa3e8bd95.1566755452.git.DirtY.iCE.hu@gmail.com> (raw)
In-Reply-To: <cover.1566755452.git.DirtY.iCE.hu@gmail.com>

This will allow us to disable mixeng when we use a decent backend.

Disabling mixeng have a few advantages:
* we no longer convert the audio output from one format to another, when
  the underlying audio system would just convert it to a third format.
  We no longer convert, only the underlying system, when needed.
* the underlying system probably has better resampling and sample format
  converting methods anyway...
* we may support formats that the mixeng currently does not support (S24
  or float samples, more than two channels)
* when using an audio server (like pulseaudio) different sound card
  outputs will show up as separate streams, even if we use only one
  backend

Disadvantages:
* audio capturing no longer works (wavcapture, and vnc audio extension)
* some backends only support a single playback stream or very picky
  about the audio format.  In this case we can't disable mixeng.

However mixeng is not removed, only made optional, so this shouldn't be
a big concern.

Signed-off-by: Kővágó, Zoltán <DirtY.iCE.hu@gmail.com>
---
 qapi/audio.json | 5 +++++
 qemu-options.hx | 6 ++++++
 2 files changed, 11 insertions(+)

diff --git a/qapi/audio.json b/qapi/audio.json
index 9fefdf5186..dc7f9cb1e2 100644
--- a/qapi/audio.json
+++ b/qapi/audio.json
@@ -11,6 +11,10 @@
 # General audio backend options that are used for both playback and
 # recording.
 #
+# @mixeng: use QEMU's mixing engine to mix all streams inside QEMU. When set to
+#          off, fixed-settings must be also off. Not every backend compatible
+#          with the off setting (default on, since 4.2)
+#
 # @fixed-settings: use fixed settings for host input/output. When off,
 #                  frequency, channels and format must not be
 #                  specified (default true)
@@ -31,6 +35,7 @@
 ##
 { 'struct': 'AudiodevPerDirectionOptions',
   'data': {
+    '*mixeng':         'bool',
     '*fixed-settings': 'bool',
     '*frequency':      'uint32',
     '*channels':       'uint32',
diff --git a/qemu-options.hx b/qemu-options.hx
index ea0638e92d..8de6deb691 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -433,6 +433,7 @@ DEF("audiodev", HAS_ARG, QEMU_OPTION_audiodev,
     "                specifies the audio backend to use\n"
     "                id= identifier of the backend\n"
     "                timer-period= timer period in microseconds\n"
+    "                in|out.mixeng= use mixeng to mix streams inside QEMU\n"
     "                in|out.fixed-settings= use fixed settings for host audio\n"
     "                in|out.frequency= frequency to use with fixed settings\n"
     "                in|out.channels= number of channels to use with fixed settings\n"
@@ -503,6 +504,11 @@ Identifies the audio backend.
 Sets the timer @var{period} used by the audio subsystem in microseconds.
 Default is 10000 (10 ms).
 
+@item in|out.mixeng=on|off
+Use QEMU's mixing engine to mix all streams inside QEMU.  When off,
+@var{fixed-settings} must be off too.  Not every backend is fully
+compatible with the off setting.  Default is on.
+
 @item in|out.fixed-settings=on|off
 Use fixed settings for host audio.  When off, it will change based on
 how the guest opens the sound card.  In this case you must not specify
-- 
2.22.0



  parent reply index

Thread overview: 27+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-25 18:46 [Qemu-devel] [PATCH 00/25] Audio: Mixeng-free 5.1/7.1 audio support Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 01/25] audio: api for mixeng code free backends Kővágó, Zoltán
2019-08-27  5:43   ` Gerd Hoffmann
2019-08-25 18:46 ` [Qemu-devel] [PATCH 02/25] alsaaudio: port to the new audio backend api Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 03/25] coreaudio: " Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 04/25] dsoundaudio: " Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 05/25] noaudio: " Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 06/25] ossaudio: " Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 07/25] paaudio: " Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 08/25] sdlaudio: " Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 10/25] wavaudio: " Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 11/25] audio: remove remains of the old " Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 12/25] audio: unify input and output mixeng buffer management Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 13/25] audio: remove hw->samples, buffer_size_in/out pcm_ops Kővágó, Zoltán
2019-08-27  5:48   ` Gerd Hoffmann
2019-08-25 18:46 ` [Qemu-devel] [PATCH 14/25] audio: common rate control code for timer based outputs Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 15/25] audio: split ctl_* functions into enable_* and volume_* Kővágó, Zoltán
2019-08-25 18:46 ` Kővágó, Zoltán [this message]
2019-08-26 13:35   ` [Qemu-devel] [PATCH 16/25] audio: add mixeng option (documentation) Eric Blake
2019-08-26 20:04     ` Zoltán Kővágó
2019-08-25 18:46 ` [Qemu-devel] [PATCH 17/25] audio: make mixeng optional Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 19/25] audio: support more than two channels in volume setting Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 20/25] audio: replace shift in audio_pcm_info with bytes_per_frame Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 21/25] audio: basic support for multichannel audio Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 22/25] paaudio: channel-map option Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 23/25] usb-audio: do not count on avail bytes actually available Kővágó, Zoltán
2019-08-25 18:46 ` [Qemu-devel] [PATCH 25/25] usbaudio: change playback counters to 64 bit Kővágó, Zoltán

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