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CVT reduced blanking: RB v1 vs RB v2

Short answer: reduced blanking shrinks the gaps around the picture, so the same resolution needs a lower pixel clock. At 4K60, standard CVT needs 712.75 MHz, RB v1 533.25 MHz and RB v2 522.614 MHz. Use RB v1 for the widest compatibility and RB v2 when you need the lowest bandwidth.

Compare them in the calculator →

Standard CVT vs RB v1 vs RB v2

VESA CVT 1.2 timings with the standard's own clock step. PixelTach's default "Exact refresh" keeps these porches and fine-tunes the clock so the refresh lands closer to the rate you asked for.

1920 × 1080 at 60 Hz

Blanking	Pixel clock (MHz)	Total (H × V)	H blank	V blank	Clock vs CVT	Sync polarity
CVT (standard)	173	2576 × 1120	656 px	40 lines	—	-H +V
RB v1	138.5	2080 × 1111	160 px	31 lines	20% lower	+H -V
RB v2	133.32	2000 × 1111	80 px	31 lines	23% lower	+H -V

3840 × 2160 at 60 Hz

Blanking	Pixel clock (MHz)	Total (H × V)	H blank	V blank	Clock vs CVT	Sync polarity
CVT (standard)	712.75	5312 × 2237	1472 px	77 lines	—	-H +V
RB v1	533.25	4000 × 2222	160 px	62 lines	25% lower	+H -V
RB v2	522.614	3920 × 2222	80 px	62 lines	27% lower	+H -V

What each one changes

CVT (standard CRT-based timing): wide blanking sized for CRT monitors to retrace the beam. Highest pixel clock. Sync polarity −H +V.
RB v1 (Reduced Blanking Timing Version 1): a fixed 160-pixel horizontal blank (48 front porch, 32 sync, 80 back porch) and at least 460 µs of vertical blank. Width is rounded down to a multiple of 8 pixels. Clock in 0.25 MHz steps. Sync polarity +H −V.
RB v2 (Reduced Blanking Timing Version 2): a fixed 80-pixel horizontal blank (8 / 32 / 40), an 8-line vertical sync and a 6-line back porch. Any width. Clock in 0.001 MHz steps, so the refresh lands almost exactly on target. Sync polarity +H −V.
RB v2 video-optimized: the 60 Hz RB v2 timing with the clock × 1000/1001, for ≈59.94 Hz video-locked systems: 133.186 MHz, 59.940 Hz at 1080p.

Which one to use

RB v1 is the safe default for LED processors, media server outputs and graphics cards. Almost everything accepts it.
RB v2 when the link is tight, for example 4K60 10-bit on DisplayPort 1.2, and the receiver supports it. Some older gear rejects RB v2. On HDMI its 80-pixel gap may not leave room for embedded audio on some sources.
Standard CVT only for older or analog-era equipment, or when a device asks for it.
CTA-861 standard formats (1080p, 4K) for TVs, projectors and broadcast converters, which often accept nothing else over HDMI.

4K60 timing details

RB v1

	Active	Front porch	Sync pulse width	Back porch	Total	Polarity
Horizontal	3840	48	32	80	4000	Positive
Vertical	2160	3	5	54	2222	Negative

RB v2

	Active	Front porch	Sync pulse width	Back porch	Total	Polarity
Horizontal	3840	8	32	40	3920	Positive
Vertical	2160	48	8	6	2222	Negative

Tip: sync polarity tells you which family a timing came from. Standard CVT is −H +V; both reduced-blanking versions are +H −V.