Visual Video Signal Errors

Encyclopaedia of Video Signal Errors

This is doc much required for archival, understanding what is a result of errors of recording onto media, physical damage on the media to errors of capture and software decoding is only possible if you understand visually.

Knowing what your looking at is key to getting the best possible results out of any media preservation or image/signal analysis.

Important

Right Click --> Open Image In a new tab to view full-size images you may miss details in a scaled page preview of them!

How to make an export

Tip

Inside ld-analyse do CTRL+S to save the current frame as a PNG file.

This will save what's displayed, we use the luma or Y channel only for error examples mostly, but errors are more variable for colour as it has to interact with the chroma-decoder, and a fully decoded to video file colour image should be made before calling it an actual error and both should be submitted.

Clean Capture & Decode

This is achieved there are little to no errors in the top VBI area or the active picture area, and the lines are consistent with each other, as can be observed with the Y/Lumma channel 4fsc examples below.

VHS PAL (Inspector Gadget 1999) - With MacroVison & Closed Captions

Video8 PAL 1995

TBC Failure

This is where the image is skewed, fields are miss-aligned, and there is lots of grainy noise in the image.

Note

This is a simulated image from a 40msps source, down-sampled RF data can result in loss of key signal information and result in issues like this, as when viewed fully the fields are not aligned.

RF Signal Loss

When a heavy signal loss occurs this is called "snowing" as it's similar to looking at a snowstorm through a window.

Note the white line is harder than a normal dropout.

RF Signal Dropout

These are dropouts or hard information loss on the physical tape, assuming there is no video head damage.

Small

Medium

Large

LaserDisc

Dropouts are normally due to disc rot and are normally hard black.

Dirty Head

This is ware one field has a drasticlly diffrent SNR when being slowly clogged.

Head Clog

One head is clogged causing one field to be filled with heavy "snow" dropouts.

Cross Hatch (Diamond)

More common on NTSC Media

Waving RF Interference

This is a very fine pattern to notice in motion very apparent on digital displays.

Chroma-Decoded Colour

Luma TBC Image

Note

This capture has the head switch position moved into the H-Sync area.

Sync Loss Error

ac3-mission00-sync-error.mp4

Horizontal Frame Jitter

ac3-sample-level_detect_divisor6.mp4

Credit & References

AV Artefacts Atlas

Compendium Of Image Errors In Analogue Video / Kompendium Der Bildstorungen Beim Analogen Video 2012 - ISBN 978-3-85861-381-7

Harry Munday - Personal Archives

DomesDay86 - Community & Members

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