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...@gmail.com>
---
Notes:
Changes from v2:
* removed #optional
qapi/audio.json | 5 +++++
qemu-options.hx | 6 ++++++
2 files changed, 11 insertions(+)
diff --git a/qapi/audio.json b/qapi/audio.json
index bd6e2494bd..7bcea6240f 100644
--- a/qapi/audio.json
+++ b/qapi/audio.json
@@ -172,6 +172,10 @@
#
# 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)
+#
# @fixed-settings: use fixed settings for host input/output. When off,
# frequency, channels and format must not be specified
# (default on)
@@ -192,6 +196,7 @@
##
{ 'struct': 'AudiodevPerDirectionOptions',
'data': {
+ '*mixeng': 'bool',
'*fixed-settings': 'bool',
'*frequency': 'uint32',
'*channels': 'uint32',
diff --git a/qemu-options.hx b/qemu-options.hx
index 098508ce09..53fc5ef453 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -432,6 +432,7 @@ 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"
@@ -500,6 +501,11 @@ 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
--
2.20.1
