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List:       kde-multimedia
Subject:    Re: Vote for a MM system (Was: Re: summary of the aKademy meetings)
From:       Marco Lohse <mlohse () cs ! uni-sb ! de>
Date:       2004-09-10 15:15:34
Message-ID: 4141C516.6080703 () cs ! uni-sb ! de
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Lennart Poettering wrote:

>That part isn't a problem. The issue is synchronization, meaning: when
>will the sample I write to the sound server now be played? It is
>impossible to solve this problem precisely. See: you're playing a
>movie on machine A using a sound card on machine B. To synchronize
>video and audio the movie player needs to know when to show the right
>video frame for the a certain sound sample. So it queries machine B:
>"what is your current latency?". This request takes some time to
>travel to machine B, let's say 10ms. Machine B replies with
>"50ms". That reply takes some time to travel back to machine A. let's
>say 5ms. The real latency is 50ms+10ms. but machine A can only
>estimate that the real latency is something like 50ms+7.5ms. (7.5ms is
>half the roundtrip time.)
>
>
>  
>
... at least for NMM, this problem (inter-stream synchronization of 
audio/video) is solved (with the help of NTP): 
http://graphics.cs.uni-sb.de/NMM/News/Events/CeBIT2004/index.html

Have fun, Marco.


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