Generate synchronized testvideo

testvideo.sh

#!/bin/bash                                                                                                                                                                                                                                                                                                                    

# Lenght in seconds
LENGTH=300

if [[ $# -lt 1 ]]; then
        echo "usage: $0 <output-file>"
        exit
fi

gst-launch-1.0 \
    mp4mux name=m ! filesink location=$1 sync=false \
    \   
    videotestsrc pattern=12 num-buffers=$LENGTH timestamp-offset=450000000 ! \ 
    'video/x-raw,width=1280,height=720,framerate=1/1' ! \ 
    videorate skip-to-first=true ! \ 
    'video/x-raw,framerate=20/1' ! \ 
    timeoverlay halignment=1 valignment=4 font-desc="sans 50" ! \ 
    x264enc bitrate=1024 key-int-max=10 ! \ 
    m. \
    \   
    audiotestsrc wave=8 num-buffers=$LENGTH samplesperbuffer=44100 ! \ 
    'audio/x-raw,samplerate=44100/1' ! \ 
    lamemp3enc ! \ 
    m.