Encoding/transkoding/transmuxing
Sum up audio-channels of a DV file:
ffmpeg -i <dvfile> -ac 1 intermadiate.wav ffmpeg -i <dvfile> -i intermediate.wav -map 0:0 -map 1:0 -ac 2 -f dv <dvfile>-dual-mono.dv
Streaming still image
ffmpeg -loop_input -f image2 -i <PATH TO IMAGE> -target pal-dv - | dvsource-file /dev/stdin