Phonon xine backend future

[Ian Monroe]

On Tue, Feb 22, 2011 at 03:29, Colin Guthrie <phonon at colin.guthr.ie> wrote:
> 'Twas brillig, and Harald Sitter at 21/02/11 21:57 did gyre and gimble:
>>> This also leads to maybe more deeper concern : do the audio processing
>>> plugins should be fixed in backend ? Could we make a interface which
>>> is backend independent - adding a possibility to the frontend app to handle
>>> the effects ? Wouldn't be this more flexible ?
>>
>> We could, if someone thought up a design that actually made this
>> possible and at the same time allowed to scale from dumb to
>> sophisticated media frameworks, I personally do not see how though.
>> That is if I understood you correctly, that the application is then
>> capable of manipulating the audio/video streams directly. Which is a
>> difficult thing as the phonon backends would have to steal the raw
>> data from the underlying frameworks, hand it to the application and
>> then feed it back into the framework once the app is done with
>> whatever it may want to do. This can not work as less frameworky
>> backends (think MPlayer or VLC) cannot do such complex things. Even
>> for those frameworks that can do it, it is extremely difficult as
>> there is no sensible way to ensure time accuracy of the data across
>> the framework, phonon and the application. That said, we already
>> provide interfaces that do not need to care about feeding things back
>> to the framework. Like AudioDataOutput with which one can operate on
>> raw audio data, but cannot feed it back into the backend, which is
>> useful for analyzers for example.
>
> Those who know me will likely know what I'm going to say......
>
> PulseAudio git master exposes an equalizer sink that can be activated
> pretty easily. There is an independent GUI that can be used but
> obviously it would be nice to just push this through to applications if
> they support it.
>
> When this is released, I fully intent to implement (or mentor: which
> reminds me I should add this as a GSoC) support for PA equalizers across
> all Phonon backends via PA (i.e. bypassing the backend completely.
>
> There are lots of things to consider about when this is and is not
> possible (e.g. you cannot equalize when using passthrough from a media
> player).
>
> In a related theme, there are also other things that will be made
> available automatically and do not require specific support in Phonon,
> like AEC (echo cancellation) that can be automatically activated when
> using the "Communications" category in Phonon. These will also "just
> happen" when PA git master is released.
>
> Obviously integrating support only for PA on Linux wont please everyone,
> but as PA is the default on most Linux distros now (even KDE based
> ones), I think it will catch a large proportion of users. And it's my
> desire to see PA supported as well as possible in Phonon, so adding such
> features is a bonus for users.

How do you plan to have this implemented? How do we make this cross-platform?

I know what we want from the end-user perspective: that the same
client code with PA would work without PA if the multimedia backend
has support for  the eg equalizer.

Ian