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

[Martin Boehme]

Kris A. Wotipka wrote:
>> AFAIK this means yuv420p colorspace, but with the standard luma range 
>> (16-234). 
> 
> To be honest, this line really helped me because it put me on the track 
> of YUV.

Actually, (almost) all digital video codecs use the YUV colour space. 
Reason being that it decorrelates the RGB components, and you can reduce 
the bandwidth for the U and V components because the human visual system 
isn't as sensitive to colour changes as it is to luminance changes.

BTW, if you're trying to learn about digital video, take a look at Mike 
Melanson's site:

http://multimedia.cx

> No one had ever suggested that I need to take this route 
> before.  I am wondering if the "p" is for "Progressive" or "PAL".  If I 
> remember right, it was decoding in the PAL format when I used it.

The "P" stands for "Planar", as Michael pointed out... it means that the 
video frame is laid out in memory such that you first have the Y 
component for the whole image, followed by the U and V components. The 
alternative would be "packed pixel"... meaning that you first have the 
Y, U and V components for the first pixel, then the YUV for the second 
pixel, and so on. (More or less... it gets a bit more complicated if you 
have chroma subsampling.)

Martin

-- 
Martin B?hme
Inst. f. Neuro- and Bioinformatics
Ratzeburger Allee 160, D-23538 Luebeck
Phone: +49 451 500 5514
Fax:   +49 451 500 5502
boehme at inb.uni-luebeck.de