[MPlayer-users] what are b frames?

[christopher j bottaro]

cool, nice answer, thanks...=)

-- christopher

On Monday 20 January 2003 02:56 pm, Frank Boehme wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
>
> christopher j bottaro wrote:
> > [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> > couldn't find much about em in the documentation or the man pages...where
> > can i go for info about em?
>
> A key frame (K-frame) is a fully encoded still picture. A D-frame is a
> frame which can only be decoded if a number of previous frames have
> already been decoded and stored in a buffer. Such frames contain only
> certain diffs to previous frames.
>
> Now, a B-frame is similar to a D-frame but it can only be decoded if
> also certain *future* frames have already been decoded and buffered. It
> contains diffs to previous and future frames. Often, codecs which make
> use of B-frames, reorder the sequence of frames in the stream so that
> upon decoding no read-ahead accesses are required.
>
> >  what do they have to do with going from dvd to divx?
>
> These issues are important when it comes to cutting video.
>
> > pros, cons, etc...?  i think i read something about they make encoding
> > more efficient (does that mean faster?) and that they can improve the
> > quaility of high motion/action scenes...
>
> Well, the less K-frames you have, the shorter the resulting video stream
> will get. But, as you van imagine, scenes which fast moving parts cannot
> efficiently be encoded with non-K-frames.
>
> Also, some codecs write only K-frames (I think mjpeg works like that).
>
> F