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List:       kde-multimedia
Subject:    Re: Video Planning Meeting
From:       Tim Jansen <tim () tjansen ! de>
Date:       2002-01-26 15:57:14
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On Saturday 26 January 2002 12:01, Martin Vogt wrote:
> Before we can speak about demuxers and
> mpeg/divx/quicktime video player in arts

Correct me if I misunderstand Arts/mcop, but as far as I have seen it is not 
possible to send encoded data (asynchronous streams) to a module without 
copying the data into a DataPacket. This is probably something you want to 
change for video en-/decoding and formats that allow zero-copying demuxing by 
passing pointers.


>    There are different image formats/colorspaces.
>    Every video codec has its own understanding of the
>    best colorspace for it.
>
>    -RGB[8..32]   (png,gif, X11 Server Standard)
>    -YUV12        (mpeg)
>    -YUY2         (M$, divx)

Agreed (but possibly RGB8 can be skipped - few people use it these days, and 
those who do are unlikely to use it for video).

Beside the raw pixels and its dimensions an image should have two other 
pieces of information:
- field information (for interlaced streams this is the information whether 
the frame contains the even or the odd lines)
- a timecode for synchronization with audio and other things


>    Result: For performance reasons we need to use shared mem,
>    but its not possible to use it always.

Is there an application that needs to transfer images from/to arts in 
realtime? Wouldn't it be easier to do everything inside the arts process, at 
least for now? 

An application that needs more functionality than arts provides should write 
a module. Even if you would use shared memory the processes need some other 
form of IPC for access synchronization and you must hope that the kernel 
really does all 60 context switches (arts->app->arts) per second that you 
need for 30fps video. This seems to make problems for audio data (where the 
cpu load is relatively low) and would make even more problems with video.

bye...

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