Thread: Mk14 vdu
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Old 25th Oct 2020, 8:48 pm   #591
SiriusHardware
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Join Date: Aug 2011
Location: Newcastle, Tyne and Wear, UK.
Posts: 11,484
Default Re: Mk14 vdu

Just to comment on Tim's video in #582, due to the strobing interaction between the TV frame rate and the phone camera refresh rate the video makes the shudder look much slower than it is, basically an electronic equivalent of 'wagon wheel spoke effect' - in reality it is 50 frames per second, with every alternate frame offset a little to the right.

- The video also makes it look as though some pixel lines are more offset than others within a single frame, but that isn't the case either. Taking two successive frames, if the first one has no offset, then in the following frame all the lines in the active screen area are offset a little bit to the right, starting at the right hand edge of the 'bright line'.

Also to reaffirm: This 'shudder' effect only occurs when the PIC is an 877A - the simplest 'cure' is to fit an 877, which makes the problem go away.

And finally, the 'shudder on graphics' effect was not present in the first two versions of firmware posted, even when the PIC was an 877A. In those versions graphics frames were all rendered with the same degree of offset as character screens - no offset.

Last edited by SiriusHardware; 25th Oct 2020 at 9:00 pm.
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