[MEncoder-users] hqdn3d versus lavc's nr

[RC]

On Thu, 3 Nov 2005 03:21:05 -0800 (PST)
Jean Hoderd <jhoderd at yahoo.com> wrote:

> Now, how do these compare exactly, and which one is
> recommended for a high quality encoding?  (And with
> which settings?)

I would certainly recomend nr, not because it's vastly faster, but
because the quality is much better than hqdn3d.  For one thing, hqdn3d
makes the video rather blocky even at fairly low values.  At values
higher than 0/1 for temporal, you get 'worms' (trails) across the screen
as objects move.  Using anything above the default value (3) for chroma
makes the picture look unacceptably washed-out to me.  With hqdn3d even
at 1:1:0, it still wipes-out fine details in the video, and makes it
somewhat blocky.  But hqdn3d doesn't reduce much noise at such low
values anyhow.  Even before nr was introduced, I would almost never use
hqdn3d (except for very noisy animation).

I don't know how anyone can say that nr is lower quality.  It does an
extremely good job of removing actual noise, without any of the
negative side-effects of hqdn3d.  Which values you should use depend on
the source...  not the noise, so much as the bitrate.  If you've got a
very high bitrate DVD that is quite noisy (eg. Gettysberg), values as
high as 600 will work well, and only cause slight blockiness. On very
low bitrate video (cheap DVDs, internet files, etc) much lower values
(100, 200) are needed to prevent blockiness, but will still get rid of
most noise.  I would never suggest anything higher than 600 in any case,
as nr does start to act badly around that level.  On the low end, as low
as 10 may be useful for cleaning-up very low bitrate material.

I've used nr extensively...  dozens of DVDs, hundreds of (analog) TV
captures, digitized VHS tapes, hundreds of short videoclips off the
internet, etc. For the most part, I find 400 to be a very good balance. 
It cleans-up most noise, and doesn't cause blockiness except on video
that was very low bitrate, noisy, and already somewhat blocky to begin
with. 

nr's other (minor) drawback is that it really pushes down the bitrate on
the first pass.  Options like naq don't help at all.  On the
second-pass, though, the bitrate will be back up to what you've
specified.  If you need to do one-pass encoding with nr, use constant
quantitizer instead of bitrate (good advice for 1pass encoding even if
not using nr).

> I didn't even know about nr until I saw it in this list.
> The manual only mentions hqdn3d -- any reason?

nr is fairly new, and you're using an old version of the man page.