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List:       kde-devel
Subject:    Re: KDE 2.0 Multimedia Support
From:       Christian Esken <esken () kde ! org>
Date:       1999-07-09 19:05:44
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Hi everybody,

before I start answering the different points, let me stress on thing at
the beginning:

We definitely need ONE filter concept for KDE - without the wheel
will be reinvented each time. If we have ONE concept, it would be
even possible to "plug in" binary-only codecs in the KDE MM
system.

IMO this is the only chance to gain access to current video
compression techniques.

So every MM developer: *Please* free your mind - think about
integrating your application in a possible KDE MM Framework.
This can mean dropping whole chunks of code - this hurts, but
it is worth the pain in case we get a real MM framework up.
The point is integration, not in killing projects.


OK, if you came until here, please consider reading the finer
parts of my mail below :-)


On Mon, 05 Jul 1999 Antonio Larrosa wrote:
>Stefan Westerfeld wrote:
>> I think there are some things to be done:
>> 
>> - Audioserver
>> 
>> We need to think how KDE2 will handle audio output from multiple
>> applications. There is KAudioServer2, I'll at least have a closer look at
>> that. I am still not sure wether a thing like GMF will actually replace
>> the audioserver, or not.
>> 
>> Anyway, we should seek to make at least some kind of audioserver ready for
>> inclusion in KDE2 as soon as possible.
>> 
>> Still, esd compatibility seems to be an issue: esd aware applications
>> should run under KDE as well. So either we directly use esd (and drop
>> KAudioServer2), or we make KAudioServer2 esd compatible.
>> 
>
>AFAIK, Christian Esken as put a lot of work on KAudioServer2 and it's
>already esd compatible. It should be (in fact, it _is_) the KDE audio
>server.

Well. I talked with Stefan on the LinuxTag. We most defintely agree that we
need ONE multimedia system for KDE. Today we have three applications that
do essentialy the same: kaudioserver, arts and kmpg.

All three use a flow system on filter graphs to process the data. Adding kwavīs
filters whe have four incompatible filter types.

That is three filter types too much! We need to pick the "best" system here.


>> - CORBA interfaces
>> 
>> There should be well defined interfaces how multimedia data is exchanged
>> between applications. GMF itself is modelled after Microsofts DirectShow
>> as far as I have understood.
>> 
>> Still, some component based audio technology would be good for KDE2 as well.
>> 
>> I think of having a parallel technology to KOM/OpenParts for multimedia
>> things as well. Not sure about that.
>> 
>
>I planned to learn CORBA and KOM by making kmid a Part. I suppose it
>should have a general interface that could be shared among multimedia apps.
>
>> - Libraries
>> 
>> There should be libraries that handle support development of good multimedia
>> applications, and reduce reinvention-of-the-wheel.
>> 
>> For instance, playing midi data should work the same for applications, no
>> matter if its sent to OSS, or sent to timidity, or sent through a software
>> synthesizer. I'll probably work with Antonio Larrossa on his classes, so
>
>Larrosa please :-)
>
>> that we can drop one of KMid(i) in for KDE2.
>
>Noone should drop his app.

Yes. But they should be migrated into KDEīs multimedia system. If it is a filter,
everybody can use it. Then kmidi would send just as many audio channels
as needed. Filters of the KDE MM system could then individually manipulate
each channel. I am sure, kmid could profit as well.


>A plugin mechanism like in KImgIO is (I think) necessary, so that companies
>can add their own formats for everyone to use them.

Yes! Very important!

>> - Filters
>> 
>> There should be video, audio and probably midi filters. These should be
>> usable in filter graphs. I have done something like that in Arts, but
>> I am not sure wether the Arts version is too optimized for realtime
>> synthesis to be useful for a whole filter flowsystem for KDE.

Itīs not clear to me, too. But on LinuxTag I agreed to take a look.

Please be aware that the arts flowsystem is fast (At least Stefan claims it). I
actually believe this, as arts creates dozens of filters on the fly. Itīs optimized
for minimum overhead.

kaudioserver has more overhead, but each filter can input n data and output
m data - it must not be known in advance how many bytes the filter creates
out of the read data.

arts reads and writes the same number of bytes in each filter. On the other
hand, arts can place loops in the filter graph. kaudioserver can do so too,
but you wonīt get the expected semantics (too big granularity in processing
data, no recursive calculation yet)


>I don't have a video capture board so I don't know how it works.
>We should talk about midi recording with Paul J. Leonard and  
>Jan Markus Wuerthner as they probably know more than us about it.
>Audio recording should be discussed with Christian I suppose.
>(Christian: does KAudioServer2 do any kind of audio recording ?)

Not yet. Surely it must be done, or kaudioserver will lack an important
feature.

>> I have some examinations (Klausuren) in two weeks. After that, I should be
>> able to work on the various things that are to be done for "good multimedia
>> support for KDE2".
>
>Ok, I finish my exams next tuesday morning, so I'll start (continue!)
>coding on tuesday afternoon :-)
>
>> In any case, a well-visible project should be created and announced then,
>> to get the different people that have done multimedia apps for KDE1
>> together, to make multimedia development under KDE2 easier and to avoid
>> permanent reinvention-of-the-wheel.
>> 
>
>Correct. Perhaps we (Christian E., you, me and everyone at kde-multimedia)
>should start the design and when we have something, we should do an
>announce for developers to help in this task.




>
>Greetings,
>
>PD: is kde-multimedia very quiet or have I been unsubscripted ?

Itīs quite. But I hope when we start a real MM framework we will have more traffic.




  Christian

-- 
Is Unix ready for the desktop? See http://www.kde.org

The                              Christian Esken
|/  Desktop                      KDE Developer
|\  Environment                  esken@kde.org

KDE - The net transparent free Unix Desktop for everyone

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