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

Michael Niedermayer michaelni
Sun Jul 24 18:27:57 CEST 2005


On Sunday 24 July 2005 17:33, Kris A. Wotipka wrote:
> Apologies and thanks for the input.  By the time I learn enough C to
> understand the code, the problem will no longer be an issue since we
> will probably be into some direct to brain transfer system with our
> entertainment.  It truly is a shame that wonderful programs such as
> these will forever be locked into the hands of those who can program but
> not write documentation.
> I as an engineer understand the issues of composite routing, syncing,
> latency, etc of the traditional studio system.  Whenever someone who
> wants to learn asks, I always try to explain it in real world terms and
> then hand them one of Grass Valleys wonderful manuals.

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?

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 //
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
how to use the filter in ffmpeg, sorry its not supported currently you would 
need to add support for that first

did any of that help you?



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