Date: Mon, 20 Apr 1998 05:17:07 +0200 (MET DST) From: Luigi Rizzo <luigi@labinfo.iet.unipi.it> To: ganzer@spawar.navy.mil (Mark T. Ganzer) Cc: hasty@rah.star-gate.com, multimedia@FreeBSD.ORG Subject: Re: High bandwidth use w/ VIC and BT848? Message-ID: <199804200317.FAA13655@labinfo.iet.unipi.it> In-Reply-To: <353AC853.E1A3751C@spawar.navy.mil> from "Mark T. Ganzer" at Apr 20, 98 04:00:00 am
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> my office. I had them both running side-by-side for a week or for test
> purposes, and found out that for a given frame rate, the FreeBSD/BT848
> combo is using double the bandwidth of the SGI Indy. I also confirmed
> this by testing the FreeBSD/BT848 system against a Sun
> Ultra1-170/SunVideo combo. It seems like VIC on the FeeeBSD is not
for an accurate test you should feed the same signal (=camera)
to both grabber inputs.
> compressing the video stream as efficiently as the SGI or the Sun, and
> was wondering what the cause could be?
In my case (PAL) there were the following problems:
* vic not using single-field capture (due to some strange
interaction with automatic format detection). interlace
might cause very noisy input.
This could be #1 candidate.
* i need(ed) to stop and restart capture to have a decent image,
or at the first start i got only half of the video lines
* the FPS command might have some bad influence on the capture.
If you want to try it, in my vic patches
(http://www.iet.unipi.it/~luigi/FreeBSD.html) there is an additional
"Threshold" slider to control the threshold above which a block is
considered "changed". this way you can get rid of noise for static
images (if that is the problem).
and finally, remember that the grabber is free running while vic is
doing compression, for moving images this might have bad interactions
with what vic reads.
also what are the conditions of test ? how about lighting, etc ?
cheers
luigi
-----------------------------+--------------------------------------
Luigi Rizzo | Dip. di Ingegneria dell'Informazione
email: luigi@iet.unipi.it | Universita' di Pisa
tel: +39-50-568533 | via Diotisalvi 2, 56126 PISA (Italy)
fax: +39-50-568522 | http://www.iet.unipi.it/~luigi/
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