[Ffmpeg-devel] ffmpeg & postprocess_internal.h (colorspace issue)

Kris Wotipka kris
Fri Jul 22 22:06:52 CEST 2005

I had first posted this in the users forum and got no response.  Maybe 
this is a developers question.  As you can see, I tried my best.  Now I 
throw myself upon the mercy of the developers...

Greetings all,

In a nutshell, I need to process .vob and mp2 video files that are in
"full Y" (luminance range is 0-255) to .mp2 with the "standard" luma
range of 16-234.

I know that this is an odd request but it is what I must do.  Now, I
know that there are no direct switches for ffmpeg but I have run across
a line in /libavcodec/libpostprocess/postprocess_internal.h

/// select between full y range (255-0) or standart one (234-16)
#define FULL_Y_RANGE    0x8000                  // 32768

now, since I am not a programmer, this makes absolutely no sense to me.
   How does 0x8000 relate to one range or the other.  I am *assuming*
that this is part of the postprocessing of ffmpeg or at least libavcodec.

After I can define this correctly, what is the proper way to call it.  I
have played around with several things but see no change in the final

So I edit postprocess_internal.h, "make" postprocess.o > make libavcodec
  > configure ffmpeg with -pp support and make ffmpeg.

I have tried values of 0x0000, 0x4000, 0x10000.  None seem to make a
difference.  I have googled till my googler was sore trying to make
heads or tails out of this file.  I would gladly RTFM if someone would
smack me with one.

Why do all of this you ask?  I work with a non-for-profit public access
television station.  More and more volunteers are bringing their
programs in on DVD.  I have gotten the mpeg data off of the disk and
converted the .ac3 to mp2 which is what the hardware needs.  Now, I need
to fix the colorspace so the whites are not clipping up to 140% of NTSC.



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