ffmpeg - How to speed up a video in order to shorten its length and embed a timestamp to represent time as it was recorded?

Question

I have a video recorded at 5 fps that I want to speed up to 30 fps to shorten it. That is simple enough as:

ffmpeg -i input.mp4 -r 30 -vf "setpts=(1/6)*PTS" output.mp4

But when I try to add a timestamp to it with:

ffmpeg -i input.mp4 -r 30 -vf "setpts=(1/6)*PTS, drawtext=text='%{pts:localtime:1610043985:%Y-%m-%d %H\\:%M\\:%S.}%{eif:mod(n,30):d}'" output.mp4

The timestamp does not longer represents the time as it was recorded (it should run faster now)

What would be the simplest way to achieve this on a single pass?

question from:https://stackoverflow.com/questions/65618190/how-to-speed-up-a-video-in-order-to-shorten-its-length-and-embed-a-timestamp-to

Answer 1

Put the drawtext filter first and then the setpts filter:

ffmpeg -i input.mp4 -r 30 -vf "drawtext=..., setpts=..." output.mp4