Eric Blake <ebl...@redhat.com> writes: > On 12/23/18 2:52 PM, Kővágó, Zoltán 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. >> >> 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 56d8ce439f..180bf207a8 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. > > The #optional tag is no longer necessary (the docs generator figures it > out from the '*mixeng' name below).
In fact, the qapi generator had special code to detect and reject #optional tags for some six months (from commit 1d8bda128d2 to 67ab1ce9263), just to ensure patches in flight don't add them. This one has been in flight for even longer. [...]