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

Kris A. Wotipka kris
Mon Jul 25 01:26:19 CEST 2005

Michael Niedermayer wrote:

> and what do you do if someone picks a completely unrelated and unused part and 
> ask you to explain it? will you tell him its not going to help him with his 
> problem even if he understands that part? or what else?
I guess that being a teacher first and an engineer second, I am more use 
to these things.  True I am not a programmer but I am trying to 1) Wrap 
my brain around the new digital formats and how they relate to my 
issues.  It's not like you can go to Books a million and buy a MPEG 
standards book off of the shelf.  Trust me I have looked.  The one I 
ordered never came in.  So, yes, I am trying to learn.

> lets see the lines you quoted:
> /// select between full y range (255-0) or standart one (234-16)
> #define FULL_Y_RANGE    0x8000                  // 32768
> the first line is a comment as it starts with //

understand that.  Now you have to understand that I have truged through 
most of the code to find this line that looked like a glimmer of hope 
for my issue.

> the second is a preprocessor directive which has the effect that all 
> occurances of FULL_Y_RANGE later in the program will be replaced by 0x8000
> now what is that FULL_Y_RANGE thing? its a flag and 0x8000 is the bit for that 
> flag, change 0x8000 to another unused bit and recompile everything and 
> nothing will change, change it to a bit which is used for something else and 
> things will break thats it
> now what does the flag/bit thing actually switch between? it switches between 
> the output range of the brightness/contrast correcture filter
> what does that filter do? it guesses the maximum and minimum brightness and 
> adjusts brightness&contrast so the guessed values are changed to the wanted 
> output ones
Sounds like exactly what I want to do.  Find everything that is <16 & 
 >235 and make it fit, clamp it, resample it, whatever to 16-235 space. 
  So you can see why I was harping on this.

> how to use the filter in ffmpeg, sorry its not supported currently you would 
> need to add support for that first
Bummer.  That statement alone would have been just fine with me.  I work 
with several developers so I know about code fragments that were put 
there and never really done anything with.  Again, I am not a programmer 
but I am a good end user.

> did any of that help you?
Yes,  I apologize if my lack of knowledge frustrates you.  I too get 
frustrated with people who want it done for them.
Like I said before, I would be more than happy to RTFM.  That is what I 
have started doing with Mplayer/coder.  As it turns out, if I can pipe 
the output of this instead of playing it on the screen, then some of my 
issues may be figured out.

I beg of the development team to come up with more complete docs. 
FFMPEG is a great program and I use it for other simpler stuff.  I will 
post this request to the list in another e-mail.

Hope you have enjoyed your weekend


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