[FFmpeg-user] How can I determine if a 10bit videofile has full 10bit video data or 8bit (+ 2bits zeros) data

[Christoph Gerstbauer]

Hello,

Can you explain me:

Why it is the last 2 bits of the FIRST byte that shows me if it is 
10bit?  Shouldnt it be the first 2 bits of the SECOND byte?
In my understanding, 8 bit are 8 digits -> first byte should be always 
full. (?)
But maybe this only is for RGB correct and not for YUV?

So why is this 10bit? ->  11111111 00000000
And why is this 8bit ? -> 11111100 00000000 (only 6bits used)

br
Christoph