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Re: [Qemu-devel] [PATCH v2 43/52] audio: add mixeng option (documentatio
From: |
Zoltán Kővágó |
Subject: |
Re: [Qemu-devel] [PATCH v2 43/52] audio: add mixeng option (documentation) |
Date: |
Wed, 16 Jan 2019 21:27:34 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 |
On 2019-01-10 02:43, Eric Blake wrote:
> 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 <address@hidden>
>> ---
>> 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).
Ok.
>> +# When set to off, fixed-settings must be also off. Not every
>> backend
>> +# compatible with the off setting (default on)
>
> Missing a '(since 4.0)' tag.
The whole AudiodevPerDirectionOptions struct is marked with 'Since:
4.0', so I don't think it's necessary.
>
>> +#
>> # @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',
>
>