[FFmpeg-user] -s[:stream_specifier] size (input/output, per-stream)

[Moritz Barsnick]

On Thu, Mar 24, 2016 at 17:05:06 -0600, jd1008 wrote:
> ffmpeg -i The_Previous_River_Trip.mp4  -s:v:1 1920x1080 -vcodec 
> mpeg1video -q:v 1 -y The_Previous_River_Trip.mp4

If you have only one video output, you are fine with just "-s
1920x1080".

> warning, clipping 1 dct coefficients to -255..255:02:37.06 
> bitrate=66271.0kbits/s
> [mpeg1video @ 0xa618f00] warning, clipping 1 dct coefficients to -255..255

That has nothing to do with a "physical" clipping of the scale, this is
a mathematical clipping in the mpeg1video encoder. (It may or may not
lead to visual impact.) I haven't seen this for a while, but I can
hardly recall when I used mpeg1video. ;-) I couldn't find a source for
this info, but remember it from "way back when", that changing the
macroblock decision algorithm may get rid of these warnings: Add "-mbd
rd" as an output option. (I just tried, it works for me.) So replace
  [...] -s 1920x1080 -c:v mpeg1video -q:v 1 [...]
with
  [...] -s 1920x1080 -c:v mpeg1video -q:v 1 -mbd rd [...]

I can't guarantee though that you won't still get one or the other
warning...

Moritz