Changes between Version 6 and Version 7 of How to speed up / slow down a video

Timestamp:

01/09/2013 01:47:28 PM (4 months ago)

Author:

evilsoup

Comment:

Added atempo filter & speeding up video and audio at the same time

How to speed up / slow down a video

@@ +1 @@
+= Speeding up/slowing down video =
+
 You can change the speed of your video using [http://ffmpeg.org/ffmpeg.html#asetpts_002c-setpts setpts] video filter.  The "old way" of creating timelapse or still frame was to first split up a video into individual frames, (for instance, as jpg's) then delete some and recombine the frames.  Using the setpts filter is the new way and is faster and possibly less lossy :)
 
 To speed up your video, you can type:
 {{{
-ffmpeg -i input.avi -vf "setpts=0.5*PTS" output.avi
+ffmpeg -i input.mkv -filter:v 'setpts=0.5*PTS' output.mkv
 }}}
 
@@ -9 +11 @@
 
 {{{
-ffmpeg -i Input.mp4 -r 16 -vf setpts=0.125*PTS -an Output.mp4
+ffmpeg -i input.mkv -r 16 -filter:v 'setpts=0.125*PTS' -an output.mkv
 }}}
 
@@ -15 +17 @@
 To slow down your video, you can type:
 {{{
-ffmpeg -i input.avi -vf "setpts=2.0*PTS" output.avi
+ffmpeg -i input.mkv -filter:v 'setpts=2.0*PTS' output.mkv
 }}}
+
+== Speeding up/slowing down audio ==
+
+You can speed up or slow down *audio* with the atempo audio filter. To double the speed of audio:
+
+{{{
+ffmpeg -i input.mkv -filter:a 'atempo=2.0' -vn output.mkv
+}}}
+
+The atempo filter is limited to using values between 0.5 and 2.0 (so it can slow it down to no less than half the original speed, and speed up to no more than double the input). If you need to, you can get around this limitation by stringing multiple atempo filters together. The following with quadruple the audio speed:
+
+{{{
+ffmpeg -i input.mkv -filter:a 'atempo=2.0,atempo=2.0' -vn output.mkv
+}}}
+
+Using a complex filtergraph, you can speed up video and audio at the same time:
+
+{{{
+ffmpeg -i input.mkv -filter_complex '[0:v]setpts=0.5*PTS[v];[0:a]atempo=2.0[a]' -map '[v]' -map '[a]' output.mkv
+}}}