Posted By
MMS
on 2020-06-27
03:51:32
 |  Re: Quality of S-Video image from a Plus/4 - mine looks bad
Also worth to mention, that the Y/C output of the C64 and C+16/C+4 are not according to the standard.
It is evident because the S-video standard formulated in 1987, while the release of the C=machines were at 1982 and 1984.
From the "264 Hardware specification" book written by Dave Haynie and Bil Herd, the vieo output signals of the 264 series is defined as 1V P-P (pitch to pitch).
If you compare it to the S-Video standard (not that easy: most of the document refers to the IEC60933-5 standard, costs 25€ just to view it), it defined maximum 0.7V level for Luma, and ~0,85V maximum for Chroma.
Fortunately there are some other good document than IEC.
So, clearly the Commodore signal is too strong for the TVs, and it causes overshoot image and/or color burst (it depends on the TV's electrical circuits, how they manage is)
Probably that's why the picture is SO much better and crisper on a Commodore monitor, despite it uses the very same signals: because the Commodore monitor EXPECTS 1V level, and is shows the perfect picture as comes out, while the TVs ar just confused (my Dell Ultrasharp monitor with SVideo and Composite inputs just refuses to show anything from Commodore. for along time I thought it is the synch (it is told to be Dell is picky to that) but now for me it is evident it is just the too high signal level)
To become more compatible with the Svideo connector at side panel or with the Scart Y/C, you need to add a resistor too, to decrease the signal level from the 1.0V to max. 0.7V at Luma(Y) and max. 0.85V azt Chroma (C) lines.
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