>>45006there is no dd or cp embedded into this, you'd have to check /bin/cp and /bin/dd for that on UNIX.
Also, if you are embedding mpeg4 videos, make sure to have -movflags faststart
tl;dr:
ffmpeg -i input.mp4 -c:a copy -c:v copy -movflags faststart output.mp4
Otherwise, most media players won't play nice with streamed stdin, and you'd have to write it to a file first, because not having faststart requires random reads for headers that are slapped at the end of the file rather than sequential ones.
Why are they at the end of the file and not in the header where they belong? Don't ask me, mpeg4 is retarded.