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Reply To: Tips & Tweaks: Lx3, Lx4, Lx5 modes

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#19053

Harrumph
Participant

No, it’s described as 5x (horizontal factor). Well, thinking about it some more, it could actually happen in two additional alternate ways, so yeah some clarification from Marqs would be neat.

Using example from previous post again, optimized 256×240 4:3 Lx3
Alt 1: described in above post
Alt 2: whole output line is actually constructed by 4x pixel repetition, only that output H active is defined as 5x, and the extra pixels to make up the difference are subtracted from blanking (ie. 128 pixels on each side of picture data). Resulting output total H.samplerate would be 341×4 = 1364. This seems unreasonable as it leaves only 1364-1280= 84 for blanking.
Alt 3: pixel repetition is applied separately for output H active and blanking. Such that blanking receives x5 and active x4. However, output H.Active is again defined as x5 and the difference made up by subtracting from blanking. Resulting output samplerate would be (341-256)x5 + 256×4 = 1449. This seems more plausible given that VESA specs for 1280×720 and 1280×768 has 1440 (in newer “reduced blanking” modes).

I don’t know regarding your observation on vertical lines. It seems less likely to be a factor to me, simply given that TVs are probably preprogrammed to recognize only certain vertical active heights.