Le 16 sept. 09 à 21:18, stephen barncard a écrit :
Animated gifs are terrible for anything with much resolution.
256 colors, indexed.
Animated gifs are good for logos and block images but not
gradients. And
they still stall in Rev if anything else is going on.
Compuserve invented and owned the patents on the .gif format up
until a few
years ago. Early on Compuserve tried to collect on every use of the
every
gif. It was a major reason for the superior open source PNG format
to be
created.
On the horizon, working today: ANIMATED PNG<http://en.wikipedia.org/
wiki/APNG>
I have to add that considering a video as a simple sequence of images
is a very inefficient concept. Most videos, most of the time, only
feature slight variations from one frame to another. Hence the idea
of including "key frames" with details and intermediary variations in
typically smaller smaller chunks of data. Detecting abrupt changes
from an image to the following one is a challenging task. The
following example shows that this notion of "abrupt change" may be
somehow subtle.
From what I remember of the draft of the future-MPEG-to-come in the
late 90's, it was supposed to include information about "video
objects". For instance, if you look at a football match (whatever
flavor) chances are that you will see interesting action in the
"foreground", i.e. players with fast movements which demand great
detail, and a more or less static background (supporters) which is
less interesting and hence, does not require high fidelity. The then-
future MPEG was supposed to separate the two components and encode
them differently. I do not know if this was ever implemented.
cheers
François
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