interlacing discussion ...

12 Jan 2000


      from video4linux list.

interesting thing; old sony digital camera with video output doesn't have 
interlacing artifacts...
...
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Date: Wed, 12 Jan 2000 13:02:02 -0800 (PST)
From: Trent Piepho <[email protected]>
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Subject: Re: Matrox Meteor II driver project?
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On Wed, 12 Jan 2000, Alan Cox wrote:
...
...
NetWinder (www.netwinder.org) that has Philips SAA7111 shows exactly the
same type of
distortions (runs Linux) during capturing dynamic videos which leads 
me to
believe it's common
problem for low-cost capture boards.
Your monitor displays at 60-100hz (hopefully 72+). The incoming TV signal
is 25fps and interlaced. You need to do extra bufffering and burn CPU time
and memory to do good delacing, or find a card that has big buffers.
This isnt a _capture_ artefact its a viewing artefact
Sure it is.  You can see interlacing artifacts just fine on still single 
frame
captures.  Take a look at http://xyzzy.dsl.speakeasy.net/~xyzzy/test.jpg, you
can see the interlacing artifacts perfectly on the scrolling stock ticker on
the bottom of the screen.
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From: H Brett Bolen <[email protected]>
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Subject: Re: Matrox Meteor II driver project?
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Broadcast sources are interlaced.  When you view a single
frame on a video monitor you are really seeing two frames
which are separated in time by 15 or 20 milliseconds.
If an edge moves a noticeable amount then you will have the zigzag
effect.  This has nothing to do with the capture, it is in the
source.
One way to get rid of the effect is to capture 320x240 instead
of 640x480.  another is to capture 640x240 and to 'double'
each of the 240 lines so that there are 480 lines.
The problem is not with capture, but with the source.  This
is why there is so much discussion about the quality of
720p vs 1020i on the HDTV boards ( interlaced vs progressive
scan ).
i is bad...... p is good.....
bï¿½
Trent Piepho wrote:
...
On Wed, 12 Jan 2000, Alan Cox wrote:
...
...
NetWinder (www.netwinder.org) that has Philips SAA7111 shows
exactly the
...
...
...
same type of
distortions (runs Linux) during capturing dynamic videos which leads
me to
believe it's common
problem for low-cost capture boards.
Your monitor displays at 60-100hz (hopefully 72+). The incoming TV signal
is 25fps and interlaced. You need to do extra bufffering and burn CPU 
time
and memory to do good delacing, or find a card that has big buffers.
This isnt a _capture_ artefact its a viewing artefact
Sure it is.  You can see interlacing artifacts just fine on still single
frame
captures.  Take a look at 
http://xyzzy.dsl.speakeasy.net/~xyzzy/test.jpg, you
can see the interlacing artifacts perfectly on the scrolling stock 
ticker on
the bottom of the screen.
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Robert Olson

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