[MPlayer-users] Need help with deblocking (-vf pp)

[RC]

On Tue, 03 Jan 2006 13:28:09 -0500
"John Brown" <johnbrown105 at hotmail.com> wrote:


> I did not see a difference between no cmp and cmp = 3, but both were
> better  than cmp = 2. 

Did you see that *cmp=3 is about an order of magnatude slower?  A good
thing to keep in mind.

> I know that the results depend on what you are encoding, but  if in
> your experience cmp=2 leads to blockiness, why does the MPlayer manual
>  suggest it for a high-quality encode? 

Well, mainly because I'm not the one who wrote the MPlayer DOCS.  But
more accurately, it's because *cmp=2 is faster than *cmp=3, while having
a PSNR value that is very close, and because most everyone watches their
videos with postprocessing/deblocking so the blockiness gets masked.

> 1) Some transitions  where one scene blends into the next (blocky 
> background)

B-frames help a lot.

> I don't think I can assume that the DVD player has block removal like 
> MPlayer.

Of course not, but at a fixed bitrate (especially at very low bitrates
like you are trying to use), deblocking can make things more blocky. 
It's better to prevent blocking in the first place (as in denoising to
make the video compress better without macroblock artifacts), and if
necessary, use options like scplx_mask which won't destroy the video.

> Creating DVDs is  neither my profession nor my hobby, and there are
> too many switches and  legal values for them for someone who has no
> knowledge of the theory of  video compression (luma? chroma?
> quantizer?) to find a solution by  searching.

Then why use mencoder?  There are many, many frontends that will make
the task much easier for a beginner.  Though the simple fact of the
matter is that it's not easy to get 720x480 MPEG2 video to look good at
such a low bitrate that you are trying to use.