[MPlayer-users] video scaling doesn't work

[Reimar Döffinger]

On Sat, Feb 15, 2014 at 07:19:58AM -0800, Grant wrote:
> >> I doubt the diff would even apply.  The only other thing I can think
> >> of would be using mencoder to prescale every video I watch up to
> >> 1360x768.  Is there a simple command for highest quality there?
> >
> > Hm, at that resolution the risk is decoding itself will be too slow. For highest quality without getting too large and causing bottlenecks elsewhere, using H.264 would be best, but it is also slowest.
> 
> I'm using the following.  Could it be improved?
> 
> ffmpeg -i input.mp4 -filter:v scale=1360:-1 -sws_flags spline -c:a
> copy output.mkv

I have no idea what that will encode as...
If it's MPEG-4 you'd probably want to set qscale (if it's still called
that in FFmpeg) to 2. If it's H.264 you will want to make sure inloop
filter and CABAC are disabled and that you use a crf value for
constant-quality. There should even be a preset for "easy to decode".
If it's anything else you'd probably want to make it use one of these
two instead, e.g. MPEG-2 for the same quality tends to actually be a bit
slower to decode due to fewer optimizations and higher bandwidth needed
- on x86, on ARM I am not sure.

> I can play that back in sync with -lavdopts fast:skiploopfilter=all:threads=3.

You should encode as H.264 CAVLC without inloop filter, at least
skiploopfilter=all shouldn't make a difference (and it will decrease
quality quite significantly when it has any effect at all).

> > I also looked into it again, installing Ubuntu 14.04. What is the result? Well, omapfb no longer exists, instead you have to use "omap" xorg driver, which does not support XVideo at all.
> 
> The omap driver supports XV and scaling if you also load the pvr-omap4
> kernel module and binary libraries

Yeah, that's why I said pandaboard is slightly better. On a beagleboard
not even that is an option.
As far as I can tell, 3D never worked on it no matter what versions you
used - this includes the "factory test image" and other similarly
ancient and unusable images that I tried anyway.