On 26 Nov 2003, Florin Andrei wrote:

> > High motion videos might benefit from '-g' being decreased - in fact
> > you could set that to 1 (if you're using the cvs version of mpeg2enc
> 
> Issues with set-top-boxes in that case?

        None.   Smaller GOP sizes just increase the filesize but allow the
        encoder to handle scene changes better.   Set -g to 1 for maximum
        flexibility.

        I have a fairly complete set of test results showing the effect
        of '-g 1 -G N' where N was varied from 1 to 15.   The effect of
        longer GOP sizes starts dropping a lot at around 10 or so.

> > I use -4 2 -2 1.   Dropping -4 from 2 to 1 increases the encoding
> > time by a lot (30 - 40%) for a nominal (couple percent at best)
> 
> ...and no visible quality gain, right?
        
        I suppose if you have golden eyeballs you might see (or imagine you
        see) a difference ;)

> > -10 is a good non-aggressive/mild setting (i've seen good results
> > with -5 to -8).
> 
> What's the default? (the equivalent if i don't use -E at all)

        0.   Meaning no effect - the single coefficient logic is not invoked
        at all.

> > 9800 is too high.   Some standalone players can not handle the maximum.
> > For portability you'll really want to back off to something like 8500.
>
> But most of the professional DVDs i've seen are at or around 9800 kb/s

        Not really.   Or rather how are you determining that?  By taking
        the .m2v streamsize in bytes and dividing by the playing time?  If
        you do that you'll find it's a rare DVD that goes over 7500.   I've
        a couple very high quality DVDs (they used a dual layer disc for a
        140 minute concert) that averaged around 6000-6500 (but they did
        include 3 audio tracks - PCM, AC3 5.1, and DTS).

        It's necessary to leave room for peaks or spikes in the bitrate -
        exceeding the legal limit even briefly will cause playback problems

        Cheers,
        Steven Schultz



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