On Sat, 19 Mar 2005, Dik Takken wrote:
> I don't know y4mdenoise yet, but is it as non-destructive as 'yuvdenoise
> -f' is?
"non-destructive"? All filtering is destructive - it changes the
original data. By non-destructive do you mean "not visibly
undesireable"? That can be subjective - a matter of personal taste.
> I will have to try if yuvmedianfilter can have a significant numerical
> impact without having significant visible effect. I'm looking for
Ah, but sometimes you _want_ visible effect - otherwise just leave the
noise present :)
> This leads me to the idea to have mpeg2enc perform this sort of numerical
> conditioning automatically on any input video. Maybe the default output
I don't see filtering as being the encoder's job. Keeping the encoder
"simple(r)" and putting the "conditioning" into a pipeline would seem
to be a better approach.
I'm not quite sure though what is meant by "numerical conditioning".
All processing on a computer is "numerical", isn't it? :-)
> quality of mpeg2enc could improve quite a bit. I read a comparison of
> mpeg2enc, ffmpeg and the tmpgenc encoder the other day and they found the
> default output quality of mpeg2enc to be a lot worse than the tmpgemc
All too often those tests are not objective. They're run by folks who
have an agenda to prove _their_ encoder is better. So they know all
the options to make _their_ encoder perform well, they don't know the
others so they take the generic/defaults and then manage to prove
their point that _their_ favorite encoder is better.
Ah, I see you mentioned "default". A better comparison would be to
have each "encoder" ("encoder" being the complete processing pipeline)
set up optimally.
mpeg2enc's defaults probably should be revised/updated but there's
no one setting that will work equally well in all cases.
You can use the TMPGENC quantization matrice with mpeg2enc if you like,
which should give similar output quality.
> output. I agree that the default output quality of mpeg2enc isn't exactly
> phenominal,
Not sure what you mean "isn't exactly phenomenal" - if the data is
not good going in then of course the output is going to reflect that.
I've used Apple's "commercial" encoder - it's good (can't be put in a
bash script, doesn't do dual-prime, allow alternate matrices, and I
haven't found the equivalent of "-D") but I can't say it's greatly
better than mpeg2enc. Haven't tried Discrete's "Cleaner" though, but
I've heard it does a good job.
> but you can get *really* good results by properly conditioning
> the input stream.
That is true for ALL encoders! Feed rubbish in, get rubbish out. Give
the encoder clean data and get clean output.
> I guess an encoder like tmpgenc is doing automatic stream conditioning to
> get such good default output quality...
Precisely! Too bad it's a windows only program (at least it was
the last I checked). I agree with your hunch that it's doing some
of what we'd do with programs in a pipeline.
Most of what folks are doing (at least it's my impression) is
converting old, noisy, poor quality original material (VHS tapes for
example). If the goal was to archive/preserve the data then one
way would be to save the uncompressed data and play that. Next best
would be to convert to a high bitrate (slightly) compressed format
(DVCPRO50) with no filtering/processing.
Most of the time a low rate DVD is the desired and to do that
'destructive' (visible) changes need to be made to the stream. It's a
compromise of how much detail to lose in exchange for the ~9.8Mb/s
rate limit. You can't have everything (all the detail) and a low
bitrate. It's a subjective judgement if the output is close enough
to the original and if not is the difference acceptable.
> > day about "desaturating the lows".
>
> Ah, maybe I picked that up while scanning my mailbox and immediately
> forgot about it again. Until now. :)
It can make a difference - it can be visible of course. But sometimes
you want a "destructive" change if it (subjectively) improves the
image ;)
> Please! Please stop teasing me with all the wonders of MJPEGTools CVS. I
> can't take it anymore! :)
Not till you update :-)
> > In the Canopus ADVC300 (if you're using or thinking of using DV)
>
> Still on my wish list..
Well worth the extra money over the ADVC100. The only downside to the
300 is that it has a small fan in it which can be heard in a quiet room
(normally it's not a problem since it's sitting next to a noisy
computer :))
Cheers,
Steven Schultz
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