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Old 10th December 2014, 22:50   #1  |  Link
aax
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Advanced image filtering for isolating hardcoded subtitles

Hi guys.
I'm extracting burned-in subtitles from some videos and have made a Photoshop action that does a pretty good job of isolating them from background when applied to screenshots (for easy OCR). So I was wondering if there is a way to get a similar effect with Avisynth because that would not only save me a step, but also improve automatic subtitle detection.

Here's what I do in Photoshop:
  • smart blur with both radius and threshold at 100%
  • high pass filter with radius around 4.2
  • new layer filled with black with blending set to "blend if" "underlying layer" is white (with white level set to around 160)
  • repeat smart blur on background layer some dozen times until I'm left with mostly clean letters (radius and threshold again at 100%)



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Old 11th December 2014, 05:02   #2  |  Link
johnmeyer
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Unless you have some reason for wanting to do this with AVISynth, I would suggest an alternative approach.

I have used a free utility on several occasions. No need to mess with Photoshop or build anything yourself. Check it out:

Subrip

It reads the hard-coded subtitles, and OCRs them. You do have to "teach" the OCR, but after it has read a few dozen subtitles, it gets pretty smart and proceeds without much additional work on your part. The OCR works pretty well, and the timing is perfect.

[edit]BTW, nice job with the Photoshop extraction. Very cool that you figured out how to do that.

Last edited by johnmeyer; 11th December 2014 at 05:03. Reason: Added comment about Photoshop extraction
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Old 11th December 2014, 05:12   #3  |  Link
feisty2
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Medianblur+mt_edge
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Old 11th December 2014, 09:58   #4  |  Link
fvisagie
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Quote:
Originally Posted by johnmeyer View Post
Unless you have some reason for wanting to do this with AVISynth, I would suggest an alternative approach.

I have used a free utility on several occasions. No need to mess with Photoshop or build anything yourself. Check it out:

Subrip

It reads the hard-coded subtitles, and OCRs them. You do have to "teach" the OCR, but after it has read a few dozen subtitles, it gets pretty smart and proceeds without much additional work on your part. The OCR works pretty well, and the timing is perfect.
I can only second your suggestion for the excellent Subrip.

Remember to save your character matrix afterwards; with each subsequent video you'll need to enter fewer and fewer unrecognised characters.

Subrip also has nicely configurable tools for bulk correction of common errors (I/l, ''/" etc.) once scanning has been completed. Do check them out.
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Old 11th December 2014, 16:26   #5  |  Link
StainlessS
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+1 on SubRip.
And Sub Edit is really very good for correcting some errors, syncing, Spell Checking + other stuff.
Sub Edit:http://forum.doom9.org/showthread.php?t=162721
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Last edited by StainlessS; 11th December 2014 at 19:30.
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