Problem setting different framerates with FFmpeg map option

Question

I am facing a problem to set video streams framerates with FFmpeg when using the map option.

Here is what I want to do:

Given an input video file of 60 fps, I want to generate an output file containing two video streams: one with 60 fps (as the source) and the other with 30 fps (half the source's framerate).

I executed this command:

ffmpeg \
  -i input_60fps.mov \
  -map 0:v \
  -map 0:v \
  -crf:v:0 23 
  -c:v:0 libx264 \
  -s:v:0 640x360 \
  -vf:v:0 fps=fps=30/1 \
  -crf:v:1 23 \
  -c:v:1 libx264 \
  -s:v:1 1920x1080 \
  -vf:v:1 fps=fps=60/1 \
  -f mp4 \
  out.mp4

This gave me the wanted output file but with streams of 60 fps!!

Am I missing something? I did many tests, I am wondering if FFmpeg has a problem to set different framerates when using the -map option!!

Waiting for your help! Thank you …

Answer 1

-vf does not accept stream specifiers. You can use e.g. -filter:v:1 for that.

However, you need not use the fps filter at all; output -r will do.

ffmpeg -i input_60fps.mov -map 0:v -map 0:v -c:v libx264 -crf 23 -s:v:0 640x360 -r:v:0 30 -s:v:1 1920x1080 -f mp4 out.mp4