[MPlayer-users] mbd, vqscale, and vpass mechanisms
D Richard Felker III
dalias at aerifal.cx
Sat Jan 3 22:38:09 CET 2004
On Sat, Jan 03, 2004 at 03:19:37PM -0500, Elmo wrote:
> [Automatic answer: RTFM (read DOCS, FAQ), also read DOCS/bugreports.html]
> I remember a discussion a while back about vqscale, but I don't believe
> a conclusion was ever really reached. Anyway, I have a few questions
> about these mechanisms in the encoding process.
> What I have typically been using as a command line to encode a dvd is:
> mencoder dvd://1 -o movie.avi -oac lavc -ovc lavc -alang en -lavcopts
> vcodec=mpeg4:acodec=ac3:vqscale=3:mbd=1 -vf crop=<foo> scale=<foo>
> I figure that this will give me a constant quality of 3, which is pretty
> much unnoticable, use the "vhq" method, which is the best quality
> encoding, and the size will be whatever is required to get the necessary
vhq/mbd=1 (same thing) should not increase quality at fixed quant,
just decrease filesize. mbd=2 might improve quality and decrease
> I don't see why people use 2-pass encoding with vqscale, basically. If
Since when do people do this??
> you're encoding at a constant quality, how does getting information
> about the bitrates help the encoding quality? Should I be doing this
> differently to get a better overall movie, or am I misunderstanding the
> way that vqscale works with vpass? Also, mbd has three options, and I
> don't really know which is the "best" in terms of quality.
mbd=2 is best. Usually encoding with vqscale isn't recommended. It
will use a lot more space and only improve quality marginally (at
best!) compared to selecting a good bitrate and using 2pass encoding.
In fact it could reduce perceived quality, since with a 2pass encode,
stills will usually get quant=2.
> Perhaps we should update the encoding-tips.txt file on the mplayer user
> site at some point, I think it's getting outdated.
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