[FFmpeg-user] difference between filter_complex and vf

[Atli Thorbjornsson]

Hi I'm trying to combined 2 files via overlay for video and amix for audio.

I have overlay working via filter_complex like this

ffmpeg -i test1.flv -i test2.flv -filter_complex
'[0]scale=iw/2:ih/2,pad=2*iw:ih[left];[1]scale=iw/2:ih/2[right];[left][right]overlay=main_w/2:0'
out.flv

But obviously this just discards the audio from test.flv
I thought the idea was to use -vf for the video and then add -af for the
audio like this

ffmpeg -i test1.flv -i test2.flv
-vf
'[0]scale=iw/2:ih/2,pad=2*iw:ih[left];[1]scale=iw/2:ih/2[right];[left][right]overlay=main_w/2:0[out]'
-af '[0][1] amix=duration=first:dropout_transition=3[out]'
out.flv

But I never get the filtergraph to work when I use -vf (even if I leave out
the -af part)
I always get this error:

Output pad "default" for the filter "src" of type "buffer" not connected to
any destination

Any ideas?

Atli.