[pulseaudio-discuss] My opinion on Tanu's "second volume control" proposal

[Alexander E. Patrakov]

06.08.2014 17:39, I wrote:
> 06.08.2014 17:11, Tanu Kaskinen wrote:
>> On Wed, 2014-08-06 at 16:35 +0600, Alexander E. Patrakov wrote:
>>> Tanu proposed:
>>>
>>>> 3) Add a second volume control to streams, one which represents the
>>>> stream's own volume only, i.e. never flat volume. Applications that
>>>> want
>>>> to avoid flat volume can use that volume control instead of the primary
>>>> volume control.
>>>>
>>>> Even if proposals 1 and 2 are implemented, I'd still like to implement
>>>> proposal 3 too, because it's simple (I need the second volume
>>>> control at
>>>> server side anyway, and adding it to the client API is just a matter of
>>>> adding one field to pa_sink_input_info and pa_source_output_info) and
>>>> because it provides some new possibilities for applications: for
>>>> example, pavucontrol could have an option to not show flat volumes even
>>>> when flat volumes are enabled.
>>>
>>> The idea is well supplanted with a use case, but I think that this could
>>> use some more discussion.
>>>
>>> The potential problem with "just exporting" the field is that the
>>> proposal specifies only one additional volume factor with no clear
>>> ownership policy, and I am afraid that various agents (the server and
>>> the client) will fight over it. OTOH, especially if we design the API to
>>> avoid "set this extra volume to this value" operation and only allow
>>> relative changes, this may as well be a non-problem.
>>
>> The ownership policy for the new volume control would be the same as
>> with the current stream volume, i.e. the user is the owner, and volume
>> changes not originating from user action are most likely a bad idea. I'm
>> not sure what kind of fight between agents you're thinking of, but with
>> this ownership policy I think there shouldn't be any conflicts any more
>> than there is with the current stream volume - stupid applications can
>> always fight with the user, but the server will only do what clients ask
>> it to do.
>
> OK, I was mistakenly under impression that the "volume changes not
> originating from user action are most likely a bad idea" policy would
> not apply to this second control. But, as it applies, there is indeed no
> fighting.

After re-reading, I changed my opinion on the proposal. My new opinion is:

The proposed feature has good justification, independent from the web 
use case, and should thus be implemented. However, when evaluating its 
positioning as a solution to the web browser 100% volume problem, one 
should keep in mind that this positioning relies on the "bad idea" 
mentioned above (because the root of the evil is that the browser 
changes the volume without user interaction). But the same also applies 
to Arun's patch. So, at best, when applied to this problem, both 
proposals are workarounds.

Still, I prefer Tanu's proposal to be implemented, as it is more general 
and has an independent use case.

For a perfect solution to the intra-application mixing problem (aka the 
web browser problem, or DirectSound emulation problem), there has to be 
a place where the "user is the owner" policy does not apply, and 
"application is the owner" policy applies instead. This implies that 
this volume factor should not be exposed in external volume control GUIs.

-- 
Alexander E. Patrakov