VCR Controls

Selects the tape recording format. Each format is characterised by its luminance recording bandwidth (TVL), the colour-under scheme used for chroma, oxide formulation and the resulting dropout statistics and mechanical transport precision.

VHS SP / LP / EP — 240 / 200 / 160 TVL. Colour-under at 629 kHz (NTSC) with 4H colour-under averaging. EP has the highest dropout rate and worst chroma noise due to the shorter recorded wavelength at slower tape speed.

S-VHS — 400 TVL. Y and C are recorded separately on separate tracks. Dramatically better luma bandwidth; compatible VHS colourunder chroma path. Requires S-VHS compatible tape (ME formulation).

Betamax — 250 TVL. Slightly better oxide than VHS SP but same colour-under principle. Sony’s half-inch consumer format, lost the format war despite often superior picture quality.

U-matic — 240 TVL. 3/4-inch professional/prosumer format. First colour-under cassette format (1971). Used extensively in broadcast ENG until the late 1980s.

Betacam SP — 340 TVL. Component Y/R-Y/B-Y recording using FM modulation, no colour-under. Y and both colour-difference channels recorded on separate heads. Near-broadcast quality; near-zero chroma phase noise because there is no colour-under heterodyne to drift.

8mm / Hi8 — 240 / 400 TVL respectively. Metal-evaporated tape in a compact cassette. 8mm uses audio FM depth-multiplexed into the video tracks; Hi8 uses the same scheme as S-VHS Y/C separation but in the smaller cassette.

Interactions: Each format changes the defaults for Tracking, Dropout, Luma Noise and Chroma Phase Noise. Betacam SP disables Chroma Phase Noise because it uses component recording. Generations loss compounds more severely with low-bandwidth formats.

How to test: Switch from VHS-EP to Betacam SP on a colour-bar source. The difference in horizontal resolution, colour fidelity and noise floor is immediately visible — the same difference that made Betacam SP the dominant broadcast acquisition format from 1986 to the early 2000s.

Head/tape alignment error. VHS heads must follow the helical tracks written by the recording machine. If the playback machine’s head geometry differs from the recording machine (different machines, worn mechanics, or a mis-set tracking control), the heads straddle two adjacent tracks and read a noisy mix of both — visible as a horizontal noise bar. At higher values, complete dropout bands appear as pure noise rectangles.

The noise bar drifts upward because the servo lock phase slips slightly each field, causing the bar to rise at the field rate until it wraps around the frame edge. This gives the characteristic “rolling” noise band seen on poorly-tracked VHS tapes.

Interactions: Combines with Skew — skew distorts the edges of the noise bar. At high Tracking + high Skew values the bar appears tilted and its edges zigzag. VHS-EP has the smallest head guard band and therefore the lowest tolerance for tracking error before dropout appears.

How to test: Set Tracking to 0.5 on VHS-SP. A horizontal noise band appears roughly one-quarter up the frame and drifts slowly upward. Adjust toward 0 to simulate the effect of tuning the tracking control on the VCR front panel.

Random oxide loss events. As the oxide coating wears off the tape, areas of missing signal appear as white or dark horizontal streaks of random length and position. The simulation models dropout events with a Poisson process — random arrival times and exponentially distributed durations, calibrated to the dropout rates measured for each tape formulation. VHS-EP at the extreme end of wear has roughly 4× the dropout rate of VHS-SP on fresh tape.

Real VCRs used dropout concealment circuits that substituted the previous line for the dropped line. The simulation does not apply concealment by default, giving the raw uncorrected dropout appearance.

Interactions: Combines with Tracking — high Tracking already loses large blocks of signal, so Dropout mainly adds the fine random sparkle on top. VHS-EP format inherently has higher dropout than SP from its shorter recorded wavelength.

How to test: Set Dropout to 0.2 on VHS-SP. Random white and dark horizontal streaks appear scattered across the image on random lines each frame. Increase to 0.5 for heavily worn tape levels.

Tape-path noise added to the luminance FM carrier. The luminance signal is recorded as an FM waveform on VHS; noise in the tape oxide layer amplitude-modulates this carrier, which after FM demodulation appears as additive noise on the Y channel. VHS HiFi audio tracks use depth-multiplexing into the same tape area, which can cross-couple as a regular beat pattern at very high luma noise levels.

Interactions: Adds to Signal Noise Level in the final composite decode. Camera Noise adds to luma before encode; Luma Noise adds to luma after the VCR decode stage. The two both appear as grain but have slightly different spectral character because one has been through the composite encode/decode chain and one has not.

How to test: Set to 0.3 and view a flat grey field. Additive grain is visible. Compare the texture with Camera Noise at the same level — they look similar but the Luma Noise grain has slightly coarser texture from the FM bandwidth limiting.

Colour-under subcarrier phase jitter. In all colour-under VCR formats (VHS, Betamax, 8mm, U-matic), the colour subcarrier is heterodyned down to a low frequency (629 kHz for VHS-NTSC) for recording. On playback, the recovered subcarrier phase jitters randomly due to capstan speed instability and tape tension variations. This phase jitter demodulates directly as hue and saturation instability: saturated colours appear to breathe and shift hue slightly from field to field.

The effect is worst in VHS-EP (lowest recorded wavelength, highest phase noise from shorter signal) and non-existent in Betacam SP (component recording bypasses colour-under entirely).

Interactions: Flutter affects capstan speed directly and therefore worsens Chroma Phase Noise. The two effects are physically coupled in real VCRs. Very high Chroma Phase Noise combined with high Saturation makes colours appear to swirl or pulse.

How to test: Set to 0.4 on VHS-SP with a fully saturated colour (pure red or blue). Watch the colour over several seconds — it shifts slightly in hue and pulses in saturation each field, giving the characteristic “breathing colour” look of worn VHS tapes.

Capstan speed variation causing horizontal displacement at the head switch point. Each helical-scan VHS track begins and ends at the head switch, at the bottom of the frame. If tape tension varies during the scan, the start-of-track position is displaced horizontally relative to the previous scan, creating a progressive horizontal lean that resets each frame at the head switch point.

At mild levels this produces the characteristic bottom-lean seen on worn tapes. At severe levels the bottom of the frame becomes a chaotic horizontal smear.

Interactions: Combines with Flutter (flutter is faster variation; skew is slower, per-scan). Head Switch Strength determines how visible the reset glitch is at the frame bottom where the skew resets each field.

How to test: Set to 0.3 on VHS-SP and view vertical lines. The bottom of the image tilts left or right. The tilt direction reverses each few frames as the capstan phase varies.

Tape copy generation loss. Each re-recording pass applies a complete additional tape noise floor, further limits the luminance bandwidth, and reduces chroma saturation. The losses compound: a 4th-generation copy has been through the tape noise floor four times, each pass adding noise and limiting bandwidth independently. This is physically accurate — every VHS dubbing pass degrades picture quality in exactly this way.

At generation 4–5, the image has noticeable horizontal blurring, elevated grain, and washed-out colours. At generation 8–10, the picture quality approaches the threshold of legibility — as seen on heavily-dubbed VHS copies of bootleg concert videos or grey-market cassette copies from the 1980s.

Interactions: Generations multiplies the effect of Luma Noise and Chroma Phase Noise — both get worse with each generation. The luma bandwidth limiting also compounds, so each generation reduces the effective TVL rating of the format further.

How to test: Set Generations to 1, view a fine pattern. Increase to 4 and compare — horizontal resolution clearly decreases, the grain floor rises, and saturated colours look less vibrant.