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bavc / avaa

AV Artifact Atlas (AVAA) is a community-built resource for identifying errors and anomalies in video files.
https://bavc.github.io/avaa/
MIT License
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BetacamSP Top Field Issue - unknown cause #250

Open jfeakes opened 3 years ago

jfeakes commented 3 years ago

Issue detected in playback of a BetacamSP tape on a Sony PVW-2800P (component out). Appears to be caused by the VTR as tapes play back fine on other decks. Initially thought it was an undersaturation issue until I split the fields, seeing that the top field was receiving no chroma signal. Link here to an additional example from another tape https://www.dropbox.com/s/m4azdie4et959k0/clip.mp4?dl=0

Field-view interleaved

michaelangeletti commented 3 years ago

It’s possible that a single field chroma loss could be attributed to a dirty (or worn/faulty) head. Betacam SP reads fields 1 and 2 on Y (luminance) tracks with two separate heads on the scanner, and fields 1 and 2 on C (chrominance) tracks with two different heads. The Betacam PALsite has a diagram of the tape wrap, head layout and tracks-on-tape layout here: http://betacam.palsite.com/format.html

Presumably, if one C playback head is clogged, you lose one field of chroma (and could misdetect as undersaturation). If two are clogged, you have a black-and-white picture. I have experienced the black-and-white output due to clogged chroma heads. Cleaning upper drum worked to resolve the issue for a while, until the tape clogged the heads again.