[FFmpeg-user] [FFmpeg-devel]Video filter "setpts" works very slow on Android

Moritz Barsnick barsnick at gmx.net
Fri Aug 19 15:48:17 EEST 2016

On Fri, Aug 19, 2016 at 12:31:49 +0200, Peter White wrote:
> is the wrong approach. I don't know if ffmpeg is capable of just writing
> different PTS without re-encoding the file. I reckon it is not. But as

That I would also like to know. I.e. whether, at least theoretically,
an input stream can be output with only changed timestamps. I
*believe* timestamps are not always part of the bitstream, so one would
have to design a path to "copy" ther bitstream, but manipulate the side

> If you must do it this way, downscaling is an option. The less pixels
> x264 has to encode the faster it runs.

You can also consider dropping some frames, as you are doubling the
framerate while timelapsing (e.g. from 25 to 50 fps). If the increased
framerate is not required for the viewer, do something like this:

$ ffmpeg -i input -vf framestep=2,setpts=0.5*PTS output

giving you only half as many frames to encode, in about half the
encoding time.

But the question remains: How to avoid reencoding.


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