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<div><span class="gmail_quote">On 30/07/07, <b class="gmail_sendername">Mark Kendall</b> <<a href="mailto:mark.kendall@gmail.com">mark.kendall@gmail.com</a>> wrote:</span>
<blockquote class="gmail_quote" style="PADDING-LEFT: 1ex; MARGIN: 0px 0px 0px 0.8ex; BORDER-LEFT: #ccc 1px solid">On 7/30/07, Steve Smith <<a href="mailto:st3v3.sm1th@gmail.com">st3v3.sm1th@gmail.com</a>> wrote:<br>
> It seems the simple problem is that FRAME sync (rather than FIELD sync) just<br>> isn't working<br>> somewhere along the line...<br><br>> The fact that we do means that the syncing system is not working somewhere
<br>> along the line, maybe it's the card, maybe the nvidia driver, maybe Myth ...<br>> does anyone know?<br><br>It's not mythtv. As far as I can tell, there is no method available<br>(with linux at least) to sync to a specific field - and I spent a
<br>lot of time looking :)<br><br>Mark<br>_______________________________________________<br>mythtv-users mailing list<br><a href="mailto:mythtv-users@mythtv.org">mythtv-users@mythtv.org</a><br><a href="http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users">
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users</a><br></blockquote></div>
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<div>Erm we don't need to sync to a specified field just the beginning of the frame (I suppose that's similar). </div>
<div>So in the case of a "PAL" signal that's 25hz at the beginning of the FRAME. </div>
<div>The video card should know when it's starting each frame, if it doesn't it's doing something very odd with interlaced output.<br>Basically if we are outputting an interlaced signal from the card, programs shouldn't really need to know. In the case of my 576i signal as far as myth is concerned it should think it's a
<a href="mailto:720x576@25hz">720x576@25hz</a> display, and receive sync at the beginning of each frame. </div>
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<div>(Looking at the specs for</div>
<div>NTSC signals it should always then send the TOP field first followed by the BOTTOM, the</div>
<div>spec uses a slightly altered sync timing between the two fields to set whether it's top or bottom so the TV/display will be able to show top followed by bottom correctly.)</div>
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<div>The fact that you can't sync to a specified field in linux leads me to think that either:</div>
<div> a) The video card/driver is sending FIELD sync i.e. 50Hz for PAL</div>
<div> b) The video card/driver is sending FRAME sync but not always at the beginning of the frame. i.e. it's a 25hz signal on a field sync boundary that's sometimes the same as frame sync and sometimes the in-between field sync.
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<div> c) The video card/driver is sending the correct FRAME sync but something else is messing up.</div>
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<div>Either way it's a bug, whether it's fixable is another matter...</div>
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<div>(Note that this only applies to driving the display using the CRT, DVI etc ports NOT using S-VIDEO/Composite as the TV out chips seem to have their own bizarre timing rules).</div>
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<div>Cheers</div>
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<div>Steve</div>
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