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bavc / qctools

QCTools (Quality Control Tools for Video Preservation) is a free and open source software tool that helps users analyze and understand their digitized video files through use of audiovisual analytics and filtering. QCTools is funded by the National Endowment for the Humanities and the Knight Foundation, and is developed by the Bay Area Video Coalition.
http://www.bavc.org/qctools
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support contextual adjustments of y-axis per graph #257

Open kieranjol opened 7 years ago

kieranjol commented 7 years ago

I couldn't think of a better issue title :( Anyhow, The VREP graph did an excellent job catching some errors ina BetaSP tape (film source) that was played back in a digibeta deck. The values were 0.0032. However, you couldn't see these spikes any more as there were some still frames at the very end of the capture that registered a value of 1.0. I wouldn't have seen the early spikes if I had pre-generated the graphs or didn't watch as the graphs generated.

Here's the view as the graphs were generating: screen shot 2017-01-20 at 17 56 41 The glitch: screen shot 2017-01-20 at 17 56 28

and finally here's what it looked like at the end: screen shot 2017-01-20 at 18 00 19

The still frame: screen shot 2017-01-20 at 18 00 40

dericed commented 7 years ago

@ElderOrb and I were discussing having contextual menus per graph so that the user could adjust the min/max of the y-axis or possibly switch between plotting log and lin. VREP is mostly only useful on analog source to show dropout compensation on TBCs, for digital tapes they are so clean that there should be lots of VREP (on color bars, titles, black, etc), even the example you showed might be a false positive rather than a 'glitch'.

kieranjol commented 7 years ago

That UI change would be useful.

The tape was analog, betasp.

As the digi beta deck was performing the analog to digital conversion for the betasp tape, perhaps there was some compensation happening? There is definitely some distortion present in those two frames and it looks like it's of digital origin.

kieranjol commented 7 years ago

I think it was a false positive, you were right. My colleague Aoife took in the same tape on a BetaSP deck with a different capture card and the exact same thing appears, so it is most likely just on the source tape.

dericed commented 7 years ago

Betacam should make some noise so I think all zeros for astats with analog audio is unlikely.

kieranjol commented 7 years ago

I'm not following you - was that comment meant for a different thread? I have astats values here..

dericed commented 7 years ago

Ha, yes sorry, mixing threads.

dericed commented 7 years ago

I'm changing the title since the idea pertaining to the y-axis is important to consider, but this isn't exactly specific to VREP. Also this ticket is related to https://github.com/bavc/qctools/issues/29.

kieranjol commented 7 years ago

👍