[MEncoder-users] lavc or xvid

[Alex Samad]

On Mon, Sep 03, 2007 at 01:47:01PM +0400, Vladimir Mosgalin wrote:
> Hi Alex Samad!
> 
>  On 2007.09.03 at 07:39:10 +1000, Alex Samad wrote next:
> 
> > > Try these xvid settings:
> > > pass=1:bitrate=2000:min_iquant=1:max_iquant=3:min_pquant=1:max_pquant=5:min_bquant=2:max_bquant=8:me_quality=6:quant_type=mpeg:trellis:chroma_me:chroma_opt:max_bframes=2:hq_ac:vhq=1:bvhq=1:keyframe_boost=15
> > > 
> > > Note that you'll probably have to increase max_ parameters if you set
> > > bitrate much lower. However, these settings aren't really suited for
> > > bitrates lower than 1200-1500 (for dvd-sized video). You don't necessary
> > > need 2k bitrate to get high quality encode, though.. On the other hand,
> > > some material (esp. noisy one) needs even more if you want it to look
> > > really good.
> > 
> > I have gone through a couple of iterations of xvid and lavc.  I have tried the 
> > above xvid options (which seem to produce a much larger file compared to lavc, 
> > compared by bitrate).
> 
> Well if you try to set 800kbit bitrate, they obviously would be bigger!
> look at that max_quant settings, they limit lowest bitrate. And if you
> hit this limit, that means that you shouldn't use these settings - the
> quality would be lower, because xvid can't use higher quants with these
> settings at all, some frames eat too much bitrate and the rest of frames
> suffer from bitrate starvation.
> 
> These options are for high-quality, "just like dvd" encodes. These
> options forbid xvid to take away quality from some frames, even if
> xvid's ratecontrol tells it so for some reason - thus making quality
> more uniform.
> 
> At 800 kbit, remove all max_?quant options and maybe keyframe_boost
> option too.
> 
> Also I'm not sure whether you should use xvid at such low bitrates (if
> you source video is dvd-sized, that is). If you need quality on this
> bitrate, your only choice is x264.
> 
> > The one thing that is a sort of unknown is I changed the camera settings to XP 
> > from normal - meant to save 10Mb instead of 5Mb to disk (higher definition ??)
> > and I am not sure when I changed it, so I am not sure which video's have it on 
> > and which have it off!
> 
> Hehe. Bad idea, to mix sources like that. However, by all means set it
> to save 10Mb, if you are reencoding anyway, at very least you want the
> source to be as good as possible.
> 
> PS you don't forget to deinterlace your video with some
> reencoding-friendly deinterlacer, do you?

Rather new to encoding/decoding.  Which is why i am trying the different bit 
rates, I wanted to see what quality I could get for what bitrate (ie size).  
The latest try with the xvid options where a recommendation from this list 
(this thread), and I saw the increase in the file size when I used the new 
options.  I am was not sure why - but you have explained that here (I think).

as for the camera, I only changed settings after stopping recording.


deinterlacer - where would I find this nice tool.  Currently I use the 
panasonic application to extract the movie form the camera comes as a mpg 
container.  and then i just re encode.  The current reason for doing so many is 
so that I can judge which is the preferred way of doing it and then setup a 
script for that - i believe i will capture 80% of my recording that way, the 
other 20% I can fiddle with.





> 
> -- 
> 
> Vladimir
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> 
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