[haiku-development] Re: Any suggestions about when and where we should call BMediaEncoder
- From: chico CHEN <chillycreator@xxxxxxxxx>
- To: haiku-development@xxxxxxxxxxxxx
- Date: Sat, 21 Mar 2009 19:45:55 +0800
Maybe I got your idea. The GSOC project should define and implement
WriterPlugin, EncoderPlugin, and then BMediaBufferEncoder and BMediaEncoder,
and some works in MediaAddOn and MediaServer. Is it right?
-chico
2009/3/21 Stephan Assmus <superstippi@xxxxxx>
> Hi,
>
> > BMediaDecoder is decodering the data of video or audio, and convert
> > them
> > to frames or chunks, and then put them into buffer. But I don't clearly
> > know where and when to use BMediaEncoder. If we add this feature in
> > MediaKit, developers will easily convert buffer data to whatever kind of
> > audio or video. Or users save some video as audio, and then the format of
> > the file will be changed. Do you have some ideas about where and when to
> > use it?
>
> I've looked through the BeBook descriptions of BMediaDecoder and
> BMediaEncoder and these classes seem to be symetrical. Unlike BMediaFile and
> BMediaTrack, these classes operate on pure media buffers, which could be
> anything, not just media files. The important thing to note here is that you
> cannot use the classes as they are. Instead, you have to write subclasses,
> in which you implement the virtual methods, for example GetNextChunk() in
> the case of BMediaDecoder. So how can these classes be used? One example:
> You have a situation not supported by BMediaFile and BMediaTrack, like
> receiving a media stream over the network, or you have created your own
> stream format for which no extractor exists. You would write your own chunk
> extractor and you could then use a BMediaDecoder for the sole purpose of
> reusing the existing decoder plugins. But you could control where the data
> is coming from that you feed the decoder plugin. BMediaDecoder is therefor a
> bridge for using the system wid
> e installed decoder plugins. BMediaEncoder would be the very same thing
> just for encoding buffers.
>
> So even though BMediaEncoder is unimplemented, implementing it does not
> automatically implement encoding support in the Media Kit. Indeed, you
> couldn't even start implementing it, since it relies on the plugins, for
> which no classes have been designed yet. These correspond to the Reader and
> Decoder classes. The GSoC project should mainly be about designing the
> Writer and Encoder classes which plugins must implement. Then the
> media_addon_server needs to be extended to manage these objects and then
> classes like BMediaEncoder can be implemented to use them, just like
> BMediaDecoder does now interface with the plugin manager to get a Decoder
> instance.
>
> Best regards,
> -Stephan
>
>
>
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