[MEncoder-users] lavc or xvid

[Alex Samad]

On Mon, Aug 27, 2007 at 10:48:37AM -0700, RC wrote:
> On Sun, 26 Aug 2007 11:22:03 -0700
> Corey Hickey <bugfood-ml at fatooh.org> wrote:
> 
> > > *cmp=2 makes for quite a bit of blockiness, and is usually a bad
> > > idea.
> > 
> > Under what circumstances? I have not observed this, though I admit I 
> > haven't done any testing of the *cmp options in a long time. 
> 
> Under all I've seen.  The only thing helped by *cmp=2 is animation
> (and it helps there a lot).  Live action suffers horribly, getting very
> blocky.  If you search the list archives, you'll find dozens of
> instances of people asking why their encoded video is so blocky (often
> with 7000kbps DVD-video encodes), being told by me or others they
> should use cmp=0/3 instead of cmp=2 (unfortunately suggested in the HTML
> docs), and it never fails that they respond and say how much better that
> looks...

I certainly have blocking and I got the options from the web site. its not 
really fast action, but definately live action, all the solid coloured area are 
blocky.

I will try removing the *cmp or aleast changing them to 0/3 and see what 
happens

> 
> And don't bother to suggesting deblocking...  I have yet to see any
> deblocking filter that is strong enough to mask blocking artifacts,
> without seriously blurring the rest of the video...  That might not be
> noticable with Xvid, which blurs everything when encoding, anyway; but I
> care about detail, at least enough to put up with a bit of blockiness.
> 
> > A long time  ago, *cmp=2 helped my tests' PSNR significantly and made
> > the encodes  look a little better.
> 
> It certainly does increase PSNR.  I have a simple fix for
> that, though...  I completely ignore PSNR.
> 
> > ...and in encodes where the bitrate is somewhat low. qns reduces 
> > blockiness around sharp edges, 
> 
> I've tried it many times, and have never seen such a benefit on live
> action.  Again, animation benefits, but cmp=2 has even more effect,
> and isn't nearly as slow as qns.
> 
> > I disagree. In my experience, 2 B-frames is optimal. The only place 
> > B-frames should hurt quality is in high-motion scenes, and an 
> > appropriate vb_strategy will avoid that. On that subject, I should
> > note:
> 
> B-frames can help a lot at low bitrates, but at high bitrates it
> usually does nothing, sometimes hurts, and at best it occasionally helps
> but very, very little.  The speed-hit is significant, however.
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