[pulseaudio-discuss] Support for audio envelopes

[Jaska Uimonen]

Hello,

For some reason the company mail server is holding back the
patches, doing some checking or what not... I sent the
patches to the mailing list last Thursday. This happened
to me once before, but I didn't remember to take it into
account...

Anyway if they are not appearing soon to the list, I will
resend them from home.

br,
Jaska


Quoting "Flavio Ceolin" <flavio.ceolin at profusion.mobi>:

> Hi folks,
>
>> Tanu Kaskinen <tanuk at iki.fi> writes:
>>
>> Hi Tanu,
>>
>>> On Fri, 2012-07-20 at 17:32 -0300, Flavio Ceolin wrote:
>>>> Tanu Kaskinen <tanuk at iki.fi> writes:
>>>> > There were problems with the code. I don't remember what exactly was
>>>> > broken, though. But at least I didn't like the concurrency handling: I
>>>> > really dislike doing inter-thread communication by using shared
>>>> > variables. Instead, message passing should be used, in my opinion.
>>>>
>>>> I'll investigate how to solve it. Btw, do you think it's better start
>>>> from the scratch or it's ok start from this code ?
>>>
>>> I really don't know. I'm not familiar enough with the code to know how
>>> much of it needs rewriting.
>>>
>>> I know that Jaska Uimonen has been working with volume envelopes too,
>>> and asked him yesterday about the status. He said he will post the code
>>> to the mailing list on Monday. I haven't seen the code, but if it's
>>> good, then it might be a good starting point too (Jaska said that it's
>>> lacking multichannel support, so work will be needed).
>>>
>>
>> It's really good to heard it.
>>
>>>> >> 2) How an application should use this code, AFAIK this code is  
>>>> not being
>>>> >>    exported.
>>>> >
>>>> > What's your use case? If we are talking about sink volume ramping, I
>>>> > don't see the need for a client interface at all, because it should be
>>>> > done automatically by the server.
>>>>
>>>> Basically I want to set an envelope which apply a filter changing the
>>>> sound balance and/or the volume, it's easier demonstrating an idea of an
>>>> envelope:
>>>
>>> But what's the use case (user-visible feature) that you're interested
>>> in? My answer to the "how an application should use this code" depends
>>> on the use case.
>>
>> I want make possible an application associate an action with an audio
>> effect. For example, a dialog pops up and you want to keep that sample
>> pattern playing but you want to "fade it out" so its really quiet. So over
>> 2 seconds you fade it out. Another example would be you shift balance to
>> the left or right according with the mobile phone (or whatever you want)
>> position.
>>
>> Regards,
>> Flavio Ceolin
>
> Trying to continue this matter, the idea of make this funcionality so
> generic is facilitating for other applications. I believe several
> applications (like media players) that use PA are implementing it's own
> "basic" effects as crossfading or fade-in/out for pause. I think make it
> easier is a goal.
>
> Other benefit of supporting it, is make possible the ducking[1] effect on
> audio streams, as we've discussed on irc, a good example for this is the
> sms case (when a sms comes the others samples should fade-out).
>
> Another point to have it is the sample cache. If the sample is already
> in the cache and the application should do fade-in/out or change the
> balance, the only way to do that is re-uploading the sample.
>
> So guys, what you think about, it worth to implement ? If not, what you
> think should be changed ? I'm open to discuss it.
>
>
> [1] http://en.wikipedia.org/wiki/Ducking
>
>
> Regards,
> Flavio Ceolin
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