Comskip: tuning for USA NTSC

[erik]

I would like to ask some attention for two tuning parameters that may require adaptation when you are using Comskip on NTSC, Comcast or with some noise on the signal.

You can check if the black level has to be adapted if you do see the letter 'u' more often then the letter 'b' below the word 'cut' in this part of the log file.

Code:

Block list after weighing ---------------------------------------------------- # sbf bs be fs fe sc len scc scr cmbnd ar cut bri logo stdev cc 0)- 30 0 30 1 805 1.26 26.827 12 0.45 2 1.57 u 76 0.54 35 1)- 32 31 1 806 889 4.31 2.769 0 0.00 6 1.57 a 26 0.00 16 2)- 2 1 1 890 1511 8.39 20.721 11 0.53 7 2.05 a 53 0.00 101 3)- 2 1 1 1512 1736 15.62 7.474 0 0.00 8 2.34 a 29 0.00 6 4)- 23 1 22 1737 1965 8.78 7.608 16 2.10 6 1.57 u 85 0.00 89 5)+ 33 22 9 1966 14150 0.00 406.539 163 3.34 0 1.57 u 66 0.86 62 6)- 11 10 1 14151 14947 16.00 26.560 205 7.72 4 2.05 a 66 0.00 285 7)- 2 1 1 14948 15055 8.00 3.570 1 0.28 4 2.20 au 54 0.00 44 8)- 1 1 0 15056 15956 5.33 30.030 21 0.70 2 1.57 u 87 0.00 35 9)- 2 1 1 15957 17775 1.00 60.661 65 1.07 0 1.57 a 92 0.00 66 10)- 12 1 11 17776 18067 4.38 9.710 7 0.72 2 2.10 ub 77 0.00 54 11)- 13 12 1 18068 18770 11.68 23.423 42 1.79 6 1.57 a 59 0.00 81

The tuning guide specifies how to tune the black level.
If you are completely uncertain how to do it and you have NTSC or Comcast I recommend the following setting in the comskip.ini file.
max_avg_brightness=25

Do some experimenting with verbose set to 5

As a result you should see much more 'b' then 'u' like this

Code:

Block list after weighing ---------------------------------------------------- # sbf bs be fs fe sc len scc scr cmbnd ar cut bri logo stdev cc 0)- 1 0 1 1 1851 4.00 74.000 54 0.73 0 1.72 a 72 0.00 94 1)+ 20 1 3 1852 17023 0.00 606.840 357 2.36 0 1.30 b 55 0.87 126 2)- 6 3 3 17024 18528 12.00 60.160 38 0.63 0 1.79 b 65 0.00 65 3)- 6 3 3 18529 19408 13.50 35.160 29 0.82 2 1.30 b 93 0.00 140 4)- 6 3 3 19409 19663 99.99 10.160 3 0.30 6 1.79 b 66 0.00 58 5)- 5 3 2 19664 20167 82.69 20.120 57 2.83 6 1.30 b 89 0.00 210 6)- 4 3 1 20168 20921 99.99 30.120 50 1.66 6 1.47 a 100 0.00 138 7)- 2 1 1 20922 21675 39.42 30.120 50 1.66 4 1.30 a 98 0.00 241

When Comskip fails to spot some commercial blocks at all this may be because you have noise in the signal.
You can check this if the block list in the log file is very short (less then 10 blocks) on a typical USA recording with at least 2 commercial blocks

In that case you may want to use this setting
non_uniformity=1000
or with a lot of noise
non_uniformity=2000

Happy tuning!