Peter Murray pete@partnercomm.com
Tue Dec 6 10:42:04 EST 2005

Garrett Wollman wrote:

>It's not a codec problem; it's a bandwidth budget problem.  DTV uses
>the standard MPEG-2 video codec; if you give it enough bandwidth, it
>will do 30 fps in 1080i without visible artifacts.  But if you're
>trying to squeeze it into 10 or 20 Mbit/s it's necessary to make some
>visible omissions.
To expand further, the problem is frame delta. The MPEG-2 compression 
algorithm relies partially on pixels remaining the same from frame to 
frame. The fewer pixels change, the less bandwidth is needed for the 
video stream. This is why some webcams can look almost photo quality, 
until something in the frame changes...


Peter Murray (N3IXY)
Vienna, VA

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