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Black bar detection not updating tag correctly

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mattkhan:
when my wife asks out of the blue "what's going on with the letterboxes", you know something is v wrong :)

jmone:
SHMBO!

Hendrik:
I'll work on adding a analysis report into a library field, so you can easily make a smartlist to check the results. It would start with a single line with a status keyword to filter on (eg. how certain it is), and then dump possible matches after.
Once thats available I can look into a heuristic to improve the selection, as it gives me more easy access to loads of data.

mattkhan:
I've realised that one of the discrepancies is with anamorphic DVDs

for example ffprobe reports for a certain dvd

SAR 64:45 DAR 16:9

MC reports the crop as 2x72x720x504 which yields an AR of ~1.4 but if you multiply that by 64/45 then you get ~2.03

for this particular film, if you set limit=16 and look at various timestamps then you get 720x432 and 720/432*64/45 = 2.37 which seems like the actually correct AR

so there are 2 problems here

1) bad crop, possibly due to the black level
2) handling anamorphic DVDs

but to add even more confusion (for me), this particular track has 2.36 in the Aspect Ratio field which implies something somewhere already knows the right answer :) Where does this value come from?

Hendrik:
A crop of 2x72x720x504 yields a frame size of 718x432, essentially the same as you say you get, so the detection seems to be working fine. (our crop values define the active video area, by left/top/right/bottom, so width/height is right-left and bottom-top)

The aspect ratio computation takes into account both the detected black bars, and the anamorphic scaling, so thats where 2.36 comes from, which is also fine (I assume it would round to 2.37 if the width wasnt being cropped by 2 pixel)

Now what actually happens when you play this? I assume something isn't right. Maybe anamorphic scaling doesnt work properly combined with black bar removal at playback time? Because the data seems fine.

Looking at the code, it should actually handle this fine as long as you are in Preserve Aspect Ratio mode or Crop mode. The only video I could find with a similar setup only had a anamorphic factor of 1.067 (720x576 being scaled to 4:3), which isn't super obvious to see, but the resulting image rectangle seems to be spot-on.

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