[Ffmpeg-devel] PATCH colortrunc

Kris A. Wotipka kris
Mon Jul 25 15:26:32 CEST 2005


Thanks for your program.  I am 100% for "doing it right" and since I 
can't look at code the way I look at a waveform meter yet I thank you 
for your input.

A little more background to help the "video purest" minds.  Quality is a 
big concern for me.  Just because the medium that I am currently having 
to work with represents two levels above noise doesn't mean it will get 
better in the future.  This facility (and a few more around the country 
who are forced to use this equipment) is starting to get flooded with 
first ammendment producers who are submitting DVD content.

The traditional way of converting them is to play the DVD as composite 
NTSC and encode in (with this "system") as a 480x480 6Kbit CBR file. 
The issue is not so much the real time encoding but the manpower to feed 
dvd after dvd into the player.

I had written a script that would suck all of the necessary vob files 
from the disk, convert the AC3 audio to MP2 and save it right into the 
server.  This was a big improvement since the data could be taken off in 
faster than real time for later process.

As for playback, the signal goes out on a very noisy RF carrier so 
artifacts, small block errors and the like are barely noticed.  Out of 
range chroma/luma however is very noticeable.

Even if this program takes a small hit in detail quality, it will buy me 
some time so that I can properly research the correct methods.

I will be out of town on business for a while but will post the results 
as soon as possible.  If you want to take this off list, my e-mail is 
kris at wotipka (dot) com.

many thanks
>> Martin
> Ok, I did some programming :-)
> * Colortrunc "truncates" the color range. If your file contains
> * colors between and including 00-0xff (ie normal 8bit) you can
> * force color 0 to be 16 .. 255 to be 234 by doing...
> *
> * ffmpeg -i infile -vhook '/path/colortrunc.so -r 16-234 -g 16-234 -b 
> 16-234' out.mov
> *
> * Note that the entire vhook argument is encapsulated in ''. This
> * way, arguments to the vhook won't be mixed up with those to ffmpeg.
> *
> * You could even invert the colors by specifying f.ex -r 255-0.
> /Marcus

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