From: Carl-Daniel Hailfinger <c-d.hailfinger.devel.2005@gmx.net>
To: lartc@vger.kernel.org
Subject: Re: [LARTC] Wireless links + Realtime video >= Headache! (long queue
Date: Mon, 28 Nov 2005 19:54:07 +0000 [thread overview]
Message-ID: <438B605F.3030001@gmx.net> (raw)
In-Reply-To: <00c301c5f451$47f89950$c901a8c0@jtwin>
Hi,
Justin Todd schrieb:
> Realtime H.263 Video (UDP) flows from the encoder to the DVR at
> 500kbit/sec peak. (avg is about 275-300). There is also a bit of
> sporatic 2-way TCP communication.
>
> ***Problem: When bit errors on the wireless link occur, video will
> get jerky and get behind (sometimes as much as 20 seconds!) and then
> suddenly the video will appear to go in fast foward and catch up
> again! This is clearly unacceptable for realtime video! We would
> rather lose the occassional packet then have it get behind.
>
> QUESTIONS:
>
> 1) will doing SNAT twice on a UDP video stream cause considerable or
> negligable delay?
Should not be measurable unless the Linux machines are totally
overloaded. For a reasonably fast machine, 100 MBit/s wirespeed SNAT is
possible, so you should be fine.
> 2) Is there a way to tell the kernel to drop a packet if its not
> delievered within an acceptable period of time?
You could try to tune the TX timeout, but I have no idea whether there
is a sysctl for that.
> 3) How can you optimize your TCP stack for realtime video?
TCP stack? I thought you were doing video over UDP. Sending video over
TCP would indeed explain your problems.
Regards,
Carl-Daniel
--
http://www.hailfinger.org/
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prev parent reply other threads:[~2005-11-28 19:54 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-11-28 19:23 [LARTC] Wireless links + Realtime video >= Headache! (long queue Justin Todd
2005-11-28 19:54 ` Carl-Daniel Hailfinger [this message]
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