[MPlayer-users] A mencoder question, incorrect bitrate.
lt at speakeasy.net
Wed Apr 21 02:33:47 CEST 2004
Xabier Rodriguez Calvar wrote:
> Hi, I'm a newbie with mencoder and have a question. I'm trying to recompress
>an mpg file with a bitrate to another file with a lower bitrate to make it
>smaller. I'm trying to make it in three passes.
> First I extract the audio. I don't want to recompress this, so I use -oac
>copy, but when making the second pass, I write the recomended bitrate to
>700MB (874) and when finishing I can see another bitrate (778,505 kbit/s).
>Which is the problem? I want to adjust it to 700MB! :-)
lavc's target bitrate is just that, a target. It adjusts the bitrate up
and down throughout the video based on the current complexity of the
video. In a video with an equal mix of complex and simple portions, the
average bitrate over the whole thing will be the rate you specified.
For most files, you'll end up with an average bitrate located somewhere
kind of near what you gave it for the target, but to get it perfect, you
have to adjust your target bitrate. If you want a true constant
bitrate, where it will be exactly what you specified all the time, I
believe the option is vrc_eq=1, but that's a bad idea.. you'll have
significant quality problems in complex sections of the video.
So you just have to keep setting the bitrate higher until the actual,
average bitrate of the file is what you want. At least, I think that's
the only option. I'm sure Rich will catch me if I'm wrong.
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