ffmpeg - merge images with video

Question

I have a video with audio that I am trying to merge with 2 images - one image before the video starts and one image after the video ends - but right now I am getting this error -

Stream specifier ':a' in filtergraph description [0:v] [0:a] [1:v] [2:a] concat=n=3:v=1:a=1 [v] [a] matches no streams.

This is the code I am using -

 ffmpeg \
    -loop 1 -framerate 24 -t 10 -i default_start.png \
    -i output-first.mp4 \
    -loop 1 -framerate 24 -t 10 -i default_end.png \
    -f lavfi -t 3 -i anullsrc \
    -filter_complex "[0:v] [0:a] [1:v] [2:a] concat=n=3:v=1:a=1 [v] [a]" \
    -c:v libx264 -c:a aac -map "[v]" -map "[a]" -y output-second.mp4 2>&1

EDIT

I am also trying to use 2 different commands, each using 1 image file instead of two --

// Image at start only
    ffmpeg -y \
        -loop 1 -framerate 24 -t 10 -i default_start.png \
        -i output-first.mp4 \
        -f lavfi -t 3 -i anullsrc \
        -filter_complex "[0:v] [2:a] [1:v] [1:a] [2:v] [3:a] concat=n=2:v=1:a=1 [v] [a]" \
        -c:v libx264 -c:a aac -map "[v]" -map "[a]" output-second.mp4 2>&1


// Image at end only
    ffmpeg -y \
        -i output-first.mp4 \
        -loop 1 -framerate 24 -t 10 -i default_end.png \
        -f lavfi -t 3 -i anullsrc \
        -filter_complex "[0:v] [3:a] [1:v] [1:a] [2:v] [3:a] concat=n=3:v=1:a=1 [v] [a]" \
        -c:v libx264 -c:a aac -map "[v]" -map "[a]" output-second.mp4 2>&1

Answer 1

You need to map the concat inputs with the corresponding file inputs:

ffmpeg -y \
    -loop 1 -framerate 24 -t 10 -i default_start.png \
    -i output-first.mp4 \
    -loop 1 -framerate 24 -t 10 -i default_end.png \
    -f lavfi -t 3 -i anullsrc \
    -filter_complex "[0:v] [3:a] [1:v] [1:a] [2:v] [3:a] concat=n=3:v=1:a=1 [v] [a]" \
    -c:v libx264 -c:a aac -map "[v]" -map "[a]" output-second.mp4