ffmpeg -f lavfi -i testsrc2=s=120x80 -f lavfi -i sine -c:a flac -ar 8000 -vframes 2 -c:v ffv1 -level 3 -c:a flac -g 1 -y reference.mkv
mkv2xml < reference.mkv > reference.xml
xml ed -L --update "/mkv2xml/Segment/Tracks/TrackEntry/Audio/SamplingFrequency" --value "0.000" reference.xml
xml2mkv < reference.xml > EBML-ELEMENT-VALID-RANGE.mkv