ffmpeg a/v sync test video

gistfile1.txt

# Rate in frames per second.
RATE=30
# Duration in seconds.
DURATION=300
# Video size options: https://www.ffmpeg.org/ffmpeg-utils.html#Video-size
SIZE=hd1080
OUTFILE=avsync_${SIZE}_${RATE}fps_${DURATION}s.webm

~/bin/ffmpeg -f lavfi -i "sine=frequency=1:beep_factor=800:duration=${DURATION}" \
  -f lavfi -i "testsrc=duration=${DURATION}:size=${SIZE}:rate=${RATE}" \
  -vf "drawtext=fontfile=/usr/share/fonts/truetype/droid/DroidSansMono.ttf: \
       timecode='00\:00\:00\:00': r=${RATE}: x=0: y=0: fontcolor=white: \
       fontsize=256: box=1: boxcolor=0x00000099" \
  -c:v libvpx -b:v 8M -c:a libvorbis $OUTFILE