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<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>OOOoooh. That also makes sense (almost…)<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>So, how do I know if linear blend is
producing 25 or 50 fps.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Basically, I want to emulate what my TV
does. With Sky, the pictures is perfect (at least to my eye), from another
thread I’m running apparently sky does no deinterlacing, and merely
passes an interlaced stream (which would have 50 “half frames”
right) to the TV. The TV then deals with it how it likes (either by
deinterlacing the image or just displaying it).<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>I want the same setup; only my problem is
it’s hard for me to have an interlaced DVI connection. So the solution
must be by deinterlacing the stream before it’s sent). OK, so what
refresh rate should I have my TV set to (I can control this using a ModeLine, I
can get as close as 50.01Hz), and what deinterlacing should I use (don’t
worry about computing power limitations, my 64 3500+ should cope with at least SDTV).
If I am to use BOB, I don’t (if I can help it), want any “BOBing”,
ie. Jumping.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>Thanks for your help.<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'>P.S. If I can set up an interlaced link,
can I then just pass the video through without deinterlacing it, therefore
allowing the TV to process it?<o:p></o:p></span></font></p>
<p class=MsoNormal><font size=2 color=navy face=Arial><span style='font-size:
10.0pt;font-family:Arial;color:navy'><o:p> </o:p></span></font></p>
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<p class=MsoNormal><b><font size=2 face=Tahoma><span lang=EN-US
style='font-size:10.0pt;font-family:Tahoma;font-weight:bold'>From:</span></font></b><font
size=2 face=Tahoma><span lang=EN-US style='font-size:10.0pt;font-family:Tahoma'>
mythtv-users-bounces@mythtv.org [mailto:mythtv-users-bounces@mythtv.org] <b><span
style='font-weight:bold'>On Behalf Of </span></b>Niels Dybdahl<br>
<b><span style='font-weight:bold'>Sent:</span></b> 02 June 2006 22:05<br>
<b><span style='font-weight:bold'>To:</span></b> <st1:PersonName w:st="on">Discussion
about mythtv</st1:PersonName><br>
<b><span style='font-weight:bold'>Subject:</span></b> Re: [mythtv-users] Having
problems / Need info on BOB Deinterlacing</span></font><span lang=EN-US><o:p></o:p></span></p>
</div>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><o:p> </o:p></span></font></p>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>On 6/2/06, <b><span style='font-weight:bold'>James Buckley</span></b>
<<a href="mailto:james@logicland.co.uk">james@logicland.co.uk</a>> wrote:<o:p></o:p></span></font></p>
<div>
<blockquote style='border:none;border-left:solid #CCCCCC 1.0pt;padding:0cm 0cm 0cm 6.0pt;
margin-left:4.8pt;margin-right:0cm'>
<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'>Actually, I'm wrong. Linear blend, or kernel, (and don't quote me on
this,<br>
this is just my understanding), convert [x] interlaced frames into [x]<br>
progressive frames, by guessing at the missing content. Seeing how BOB is <br>
listed as giving 2x framerate, that must mean 2x the others (IE linear blend<br>
and kernel), therefore BOB deinterlacing must give [2x]. So for example with<br>
PAL TV, BOB must give a 100fps output. Therefore BOB deinterlacing is best <br>
used with a monitor that can have a 100Hz refresh. The reason the screen<br>
jumps is a side effect, but it's removed when you only see exactly half the<br>
frames BOB is outputting (IE on a 50Hz TV). On a 100Hz refresh monitor or <br>
TV, every frame will jump, but at a 100 times a second, it probably isn't<br>
very noticeable.<br>
<br>
Sorry for the long babble, only just worked it out...<o:p></o:p></span></font></p>
</blockquote>
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<p class=MsoNormal><font size=3 face="Times New Roman"><span style='font-size:
12.0pt'><br>
I think it is a little different. Interlaced PAL has 25 frames per second. Each
frame consists of two "fields": A field with the even lines and a
field with the odd lines. So the field rate is 50 fields per second. <br>
An almost static image will display with the full resolution of 576 lines while
a moving image will have the resolution at 288 lines as the two fields dont
fit, (which creates the combing effect on progressive displays), but keeps the
display updated at 50 Hz. <o:p></o:p></span></font></p>
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<p class=MsoNormal style='margin-bottom:12.0pt'><font size=3
face="Times New Roman"><span style='font-size:12.0pt'><br>
The description of the linear blend filter says that it averages each line with
the value of the next line (which is taken from the opposite field). This
calculation require two fields, so it could be done once per frame or once per
field, which would give either 25 frames or 50 frames per second. I have not
been able of finding exact information on this. However it is impossible to
create information that is not there, so it can not create a resolution of 576
lines at 50 Hz, so the real resolution is equivalent to 288 lines. You might
imagine an example where all the odd lines are black and all the even lines are
white. Averaging the lines as described will give a uniform gray image, so the
linear blend filter reduces the resolution by a factor of 2 for still images
and also might reduce the update rate by a factor of 2 depending upon how often
the calculation is done. <br>
<br>
My understanding of Bob is the lines in each field are doubled, so that each
field makes a frame. The frame frequency for PAL will then be 50 Hz which is
twice that of the interlaced signal. But the resolution is reduced to 288
lines. Again imagine the example of even lines being white and odd lines being
black. This should blink between completely black and completely white frames.
So it can not show a resolution of 576 lines. <br>
<br>
In the description of the "transcode" tool on <a
href="http://www.transcoding.org/cgi-bin/transcode?Transcode">http://www.transcoding.org/cgi-bin/transcode?Transcode</a>,
there are mentioned deinterlace functions named smartdeinter and smartyuv,
which only reduces the resolution on moving parts. Why doesnt MythTV have such
a filter? Does it take too much processing power? <br>
<br>
Niels Dybdahl<o:p></o:p></span></font></p>
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