[haiku-development] Re: GSoC for MediaKit
- From: "chico CHEN(chao CHEN)" <chillycreator@xxxxxxxxx>
- To: haiku-development@xxxxxxxxxxxxx
- Date: Sat, 21 Mar 2009 16:08:59 +0800
Hi,
I have read part of codes about the MediaKit in
http://dev.haiku-os.org/browser/haiku/trunk/src/kits/media. And find the
BMediaEncoder is not implement. Is there any non-implement task in MediaKit?
Or I just use this one as my GSOC project?
The media_addon_server is PluginManager. Is it right?
-chico
2009/3/21 Stephan Aßmus <superstippi@xxxxxx>
> chao chen schrieb:
>
>> Hi,
>> You said that," The Haiku implementation defines an API for writing
>> Reader and Decoder plugins:". Can you show me some subclasses?
>>
>
> They are all in src/add-ons/media/plugins/ For example:
>
> <
> http://dev.haiku-os.org/browser/haiku/trunk/src/add-ons/media/plugins/avcodec
> >
>
> And you said "you should read enough in the BeBook documentation to get
>> an overview of the client API that is related to decoding and encoding media
>> files. Next, you should try to become familiar with the flow of the code
>> between libmedia.so, media_server and media_addon_server." You mean that
>> there are client-server structure.
>>
>
> In some respects, in some not. For Media Nodes, it is more like a
> client/server structure, where the media_server mainly manages
> cross-application communication, shared memory, notifications, and stuff
> like that. For encoding/decoding, the server only keeps track of what
> plugins there are and which formats they decode/encode. What I mean by
> "client application" is just "an application which uses the Media Kit API",
> ie libmedia.so and it's C++ classes. So for decoding, the C++ code in
> libmedia.so does communicate with the media_server and media_addon_server,
> but only to get an entry_ref (something like a file handle information) to
> the right plugin. Then the actual plug-in loading and object instantiation
> happens fully inside the client application and the server has nothing to do
> with it anymore.
>
>
> And is there uml diagram to show the relationship among classes?
>>
>
> Unfortunately no, I don't believe so.
>
> The client has encoder and decoder. I want to know where the
>> ReaderPlugin.h DecodePlugin.h EncoderPlugin.h should be used?
>>
>
> See above, it's used only in those plugins, and some libmedia.so classes
> that directly deal with those plugins. I don't know off-hand which ones. But
> it should be easy to grep the code to get a first overview.
>
> Is the work stream like:
>> media_addon_server is like a backend service and montor the folder. If
>> someone puts a new plugin in the folder, the media_addon_server will update
>> its formats. Then client application starts, requests the information from
>> media_server, and media_server gets the format from the media_addon_server,
>> then media_server encode or decode the media and send the information to
>> client?
>>
>
> For the most part, this is correct. The format for the current file is
> somehow constructed, I have forgotten how that is done. I don't remember if
> each decoder plugin is given a chance to identify the file, or if the format
> is constructed another way. I believe it's done another way and only those
> plugins get to look a the file which are potential candidates. (David/Marcus
> please correct me, if I am wrong.)
>
> Anyways, the decoding the happens fully in the application, the servers are
> not involved in that anymore.
>
>
> I didn't think clearly about this yellow part. Because the client has
>> its encoder and decoder, the media_server only send the format to the
>> client?
>>
>
> The client sends the format, the server tells it what plugin to use. You
> definitely need to look at the src/kits/media code to get the full picture
> and the most precise information.
>
> Best regards,
> -Stephan
>
>
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