[MPlayer-users] AVI encoded file playback on other systems

Karl Ewald karl.ewald at ixos.de
Wed Sep 24 19:29:14 CEST 2003

Corey wrote:
>Actually, you really should be using 2-pass mode to encode anything you
>want to keep. On the first pass, the ratecontrol algorithms can only
>guess which future parts of the video will need a higher bitrate (such
>as when the picture changes rapidly) and which will need only need a
>small amount. The second pass then uses statistics from the first pass
>to better allocate data, resulting in a file with more consistant

As far as I understand, if I use constant quantizer I should get uniform
quality at the expense of unpredictable filesize. So it allocates the amount
of data needed for the requested quality anyway, and two pass mode wouldn't
make any difference. Only if I want to match a target filesize, two-pass
would raise or lower the quality uniformly to make the resulting file match
the target size.

While I do not specify a constant quantiser with vqscale, I use very narrow
bounds for the quantiser, e.g. vqmin=7:vqmax=8. With a (too) small target
bitrate this should act identical to vqscale=8 since the vqmin/vqmax
corridor takes precedence over the target bitrate, and my remark above

I can live with the variable filesize resulting from this approach, since
for given material  (e.g. episodes of the same series) I quickly gather an
idea of the range of filesizes usually produced.

Is what I'm writing here basically correct or am I mistaken?



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