Hi
On Thu, Aug 6, 2015 at 8:28 PM, Kővágó, Zoltán <dirty.ice...@gmail.com> wrote:
> 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.
>
Since the setting is so complicated, shouldn't it be a OnOffAuto? and
let the backend decide what's best for the user?
> 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>
> ---
> qapi/audio.json | 5 +++++
> qemu-options.hx | 6 ++++++
> 2 files changed, 11 insertions(+)
>
> diff --git a/qapi/audio.json b/qapi/audio.json
> index b57b215..0216a10 100644
> --- a/qapi/audio.json
> +++ b/qapi/audio.json
> @@ -184,6 +184,10 @@
> #
> # General audio backend options that are used for both playback and
> recording.
> #
> +# @mixeng: #optional 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: #optional use fixed settings for host input/output. When
> # off, frequency, channels and format must not be specified
> # (default on)
> @@ -207,6 +211,7 @@
> ##
> { 'struct': 'AudiodevPerDirectionOptions',
> 'data': {
> + '*mixeng': 'bool',
> '*fixed-settings': 'bool',
> '*frequency': 'int',
> '*channels': 'int',
> diff --git a/qemu-options.hx b/qemu-options.hx
> index 60a3563..bd922bf 100644
> --- a/qemu-options.hx
> +++ b/qemu-options.hx
> @@ -329,6 +329,7 @@ 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"
> @@ -397,6 +398,11 @@ 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
> --
> 2.4.5
>
>
--
Marc-André Lureau
