[gst-devel] [ffmpegcolorspace] rgb 2 yuv

[Wai-Ming Ho]

Hi,

On Monday 27 April 2009 15:12:05 Julien Isorce wrote:
> Hi,
>
> When I convert a pure black image to yuv using ffmpegcolorspace, then y is
> equal to 16, u and v are equal to 0.
>  If the input is pure white then y is equal to 251.
>
> proof:
> gst-launch-0.10 videotestsrc num_buffers=1 pattern=2 ! "video/x-raw-rgb,
> bpp=24, depth=24, width=4, height=4" ! ffmpegcolorspace ! "video/x-raw-yuv,
> format=(fourcc)YUY2" ! filesink location=black.yuv
>
> then hexedit black.yuv ->
> (y1 u y2 v)
> 10 80 10 80 ->  16 128 16 128
> 10 80 10 80
> 10 80 10 80
> 10 80 10 80
>
> The 128 is ok but I do not understand why y is equal to 16. Why not 0 ?

see some explanations here: http://www.fourcc.org/fccyvrgb.php

cheers,
waiming

>
> Sincerely
>
> Julien