interlacing discussion ...

[Robert Olson]

from video4linux list.

interesting thing; old sony digital camera with video output doesn't have 
interlacing artifacts...

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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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 >
 >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.....
 >
 >b²
 >
 >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.
 >>
 >> --
 >>          To unsubscribe: mail video4linux-list-request at redhat.com with
 >>                        "unsubscribe" as the Subject.
 >
 >
 >--
 >         To unsubscribe: mail video4linux-list-request at redhat.com with
 >                       "unsubscribe" as the Subject.