[Ffmpeg-devel] Differences between mencoder andffmpegwhenencoding using x264

[Luca Abeni]

Hi Erik,

On Tue, 2006-02-21 at 11:16 +0100, Erik Slagter wrote:
> On Tue, 2006-02-21 at 03:45 +0000, Robert Swain wrote:
> 
> > I did this because qscale means nothing to me while I (and other x264 users to 
> > my knowledge) are much more familiar with 'qp's. 'qscale' was originally used 
> > but as most x264 users (due to use of the cli or mencoder) I changed it to 
> > cqp. I will take all the flak for this decision.
> 
> [ ... ]
> 
> > As Loren said, x264 uses the subme option to control such techniques and as 
> > such I tried to avoid use of *cmp.
> 
> Hmmm, maybe an idea, if these (mpeg4-specific) parameters are used for
> h264 encoding, to either submit a warning or silently try to the
> translate the parameters into h264 semantics as much as possible?
This is kind of what I would expect from libavcodec/x264.c

> Currently nothing is reported and the supplid values are silently
> ignored, which is imho very wrong, because the user (me ;-)) has no clue
> what's going on!
Exactly!
I spent a lot of time comparing mpeg4 and h.264 videos trying to
understand why "fixed quality" H.264 looked so "variable"...
Then, I finally discovered that the ffmpeg "-qscale" (which means "use
fixed video quantiser scale") option does not do anything when encoding
H.264... Not very intuitive :(

If libavcodec/x264.c screamed, telling me that I was using the wrong
command line option, that would have saved me a lot of time.
Same for the "-loop" option: if it is not selected, libavcodec/x264.c
should complain (maybe printing a warning like "WARNING: In-Loop
Deblocking filter not selected, so good quality cannot be expected"), so
that I know that I'm doing something wrong... This will surely save a
lot of time to future users :)


				Luca
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