[MPlayer-users] Mencoder: are the displayed bitrates accurate?

[D Richard Felker III]

On Mon, Oct 27, 2003 at 03:40:32PM +0100, Levente Novák wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> I would like to encode with a given maximal video bitrate (say 2500 
> kbps), what mencoder with a 2-pass run seems to perform without problems 
> (all bitrate values displayed during the encoding process are below this 
> threshold). However, if the resulting AVI or MPEG is loaded into 
> avidemux2 (which has a nice bitrate histogram tool), this latter shows 
> that some frames are apparently encoded with much higher kbps values 
> than 2500.

Of course. A bitRATE is a rate, which means it involves bits and time.
MEncoder's numbers are for the whole file, i.e. total bits/total time.
Computing a bitrate for a single frame is very silly, since obviously
some frames will take many more bits (easily up to 100x more) to
encode than others.

Sometimes you're forced to stay within bitrate constraints over some
short period of time, e.g. for streaming over slow networks of off of
slow media. You can try to accommodate these situations using the
min/max rate and buffer size options, but I don't expect you'll have
good results.

Rich