[MEncoder-users] improving x264 encoding quality ?

[Guillaume POIRIER]

Hi,

On 12/8/06, Pierre Catello <pierre.catello at gmail.com> wrote:
> Hello,
>
> I have endoded a DV footage with lavc and x264, and to my surprise the
> lavc version is much better at 1500 kbs/s than x264 at the same
> bitrate on situation with many moving details:
> - it is a surfing footage with horizontal panning, breaking waves, and
> wind chop (many bumps at the surface of the water = many small edges).
> The wind chop becomes very blurry both at the foreground and the
> backgrouynd, which looks very unnatural.
>
> but lavc kept these zone well detailed.
>
> The settings used were the following (second pass):
>
> for lavc:
> vcodec=mpeg4:mbd=2:vbitrate=2500:mv0:trell:v4mv:cbp:last_pred=3:predia=3:dia=3:vmax_b_frames=2:vb_strategy=1:precmp=3:cmp=3:subcmp=3:preme=2:qns=2:mpeg_quant:vpass=2
>
> for x264:
> subq=6:frameref=15:8x8dct:bframes=3:b_pyramid:weight_b

I don't see any bitrate here (while you put it in lavc list of
options). Maybe you forgot to copy it here, but just in case, you may
want to check that your actual commandline has bitrate option set
correctly.


> Naturally, i would expect a higher quality (or at least the same) from
> x264 at the same bitrate. How could I improves things (keeping the
> details, like lavc) ?

> - it is recommended not to "play" with deblocking, do you think that
> in my case it would be appropriate to reduce the deblock filter ?

The section of the doc that says that deblocking settings should not
be changed is bogus. It should be changed someday.
To preserve the maximum of details, provided that you throw prenty of
bandwidth at the encode, you can safely set deblocking to -6,-6.
I'd suggest trying -3,-3 before trying -6,-6 though.


> - or are there other options that would improves the preservation of details?

You can try some of the encoding examples listed in this section:
http://www.mplayerhq.hu/DOCS/HTML/en/menc-feat-x264.html#menc-feat-x264-example-settings

and also look for more info in the man page if you want.

Guillaume
-- 
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