[vlc-devel] Re: Overhead and JXTA

[Sigmund Augdal]

On Tue, Apr 05, 2005 at 04:24:53PM -0300, Giovane Moreira wrote:
> Hello Folks,
> 
> I'm studying the vlc performance while I'm streaming multimedia content. 
> I streamed a MP3 file (cbr 128kbps) to another machine, 1 hop
> distance, and I used snmp to monitoring my ethernet card. I found out
> that I need 186,31 kbps (average) to transmit this mp3 file (cbr
> 128kpbs). In my research I'm trying to measure how much overhead is
> generated on many different scenarios.
> 
> So I started guessing: -Who's responsable for this overhead? 
> In tcp/ip stack, we have:
> 
> Application layer: that's where VLC mount the package. JXTA protocol
> is used here (that's what ethereal showed me on my linux box)
> 
> Transport Layer: VLC use UDP (and there's a little bit overhead here
> too - 64 bits per udp package)
> 
> Network Layer: IP protocol - a lot of overhead here... IP has many field 
> 
> Link Layer: Ethernet  overhead.
> 
> So here I am: Is my approach correct? I'm justing summing all fiels of
> non-data(I mean, metadata, the data except the mp3 file... such
> checksum, port, source fields) of all protocols used in all layers in
> transmittion. So if I sum all this then I got my overhead. Is this
> correct?
> 
> Example: transmit 100 bytes of mp3 file. I should then add the JXLA
> overhead (couse of JXLA protocol fields and other protocols). So I
> should add UDP overhead (64bits per package) then IP overhead(192bits
> per package) and then Ethernet Overhead(26bits per package).
> 
> I'm supposing that snmp count all this data.And I got who's generating
> the overhead. Is this ok:?
in general, for streaming media you have application layer protocol and
container format. Both these add overhead to the bare codec data. These are 
specified using access and mux keywords when
constructing a vlc stream output. Vlc have several, so you need to tell
which ones you are using if we are to give useful feedback.

> 
> And other question: Why VLC uses JXTA? Why not another api?
never heard of that. Quite sure there are some mixup there.


-- 
Sigmund Augdal
Edgar B. Schieldropsv 29-14
N-7033 Trondheim
Norway
tlf: 91809129

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