[MPlayer-users] video scaling doesn't work

Grant emailgrant at gmail.com
Sat Feb 15 21:18:58 CET 2014

>> 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 tried scaling in ffmpeg with -tune fastdecode which seems to really
lighten the load on mplayer.  I'll report back with any more findings.

- Grant

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