Does anyone on this list know how I can change the hue of a video
inside of the encoding pipeline? I made a recording with my
camcorder and I forgot to do the proper white-balancing prior to
the recording. As a consequence, I now have a DV file on my
computer that has incorrectly calibrated colors, and I want to
correct those colors before I encode the file to mpeg1/mpeg2.
I've done that a few times. What you want is yuvcorrect. Here's some
examples I've used to correct white balance:
# approximate white balance correction for indoor (incandescent light) shot
# using outdoor white-balance setting.
yuvcorrect -M RGBFIRST \
-R R_1_0_255_0_180 \
-R G_1_0_255_0_215 \
-R B_1_0_215_0_255 \
-Y Y_1_0_190_0_255
# a milder version
yuvcorrect -M RGBFIRST \
-R R_1_13_224_0_255 \
-R G_1_12_204_0_255 \
-R B_1_0_176_0_255
# outdoor natural light shot with indoor white-balance
yuvcorrect -M RGBFIRST \
-R G_1_0_255_0_185 \
-R B_1_0_255_0_180 \
-R R_1_0_180_0_180 \
-Y Y_1_0_220_0_255
Note that in each case I'm not just adjusting white balance (which
would just involve shifting), but also scaling to maximize contrast.
These were in some cases ad-hoc tweaked until I liked how it looked,
or in some cases I pulled a screenshot into the Gimp and checked out
the histogram, etc.
You can do some of the same stuff in YCbCr directly, but RGB is just
easier to think in.
What I'd really like is a tool that will scan the clip (or part of it)
and automatically correct white balance and/or maximize contrast.
Hand tweaking of yuvcorrect parameters is tedious.
Dan
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