ffmpeg -i recorded.mpg -vn recorded.wav

audacity rendered.aiff recorded.wav
# soften ping part
# cut pieces such that they match the recorded ones

ffmpeg -i recorded.mpg -i rendered-cut.wav -map 0.1 -map 1.0 combined.mpg
# it seems that ffmpeg does not support the order audio-video,
# as it appears in recorded.mpg from the camera

# '-acodec copy' leads to warnings on encoding and replay
# '-vcodec copy' leads to desynchronized video and audio
# thus I encode with high bit rate