[MPlayer-users] Why create video in 1st pass?

[Guillaume POIRIER]

Hi,

On 11/24/05, Tshepang Lekhonkhobe <tshepang at gmail.com> wrote:
> > In any case, the codec still does have to encode the video to collect
> > stats about it, so there's no way (that I know of) to short-cut this
> > step of the encoding process.
>
> From above statement, I assume this is not a possible scenario:
> a) source file is .VOB
> b) decode it to raw video
> c) collect stats by studying raw video
> d) reencode it to .AVI using stats

indeed, it's not

(in theory, it should be possible to collect some fairly inaccurate
stats [like bitrate of the source] from the RAW video, but this won't
be of much help as what the codec wants to know is how does the the
source compresses depending on a given set of encoding options)

> and this more correct:
> a) source file is .VOB
> b) decode it to raw video
> c) reencode it to .AVI
> d) collect stats by studying .AVI

No, the stats are not generated studying the AVI, the codec generates
those stats internally (probably after each frame has been produced).


> or do we get rid of (b) in which case the .VOB to .AVI conversion is
> done directly?

Nope. You can trust me on this: don't try to save a bit of CPU time by
trying to reduce resource usage of a task probably that only takes
less than a percent of the total encoding process. Please read this
article: http://en.wikipedia.org/wiki/Amdahl's_law

Guillaume
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