BEGIN {
    RS="--\n"
    ORS="\n"
    FS="[=\n]"
    frm=0
    offset=0
}
# A typical record looks like:
# pkt_pts_time=166.725833
# pkt_pos=596336
# pict_type=I
# coded_picture_number=13
# interlaced_frame=0
# --
{
    pkt_pts_time=int($2*1000+0.5)
    pkt_pos=$4
    frame=$8+offset
    if (frm==0) {
	startpts=pkt_pts_time
	# a bug? in ffprobe makes the frame numbers deficient by 2 after frame 0
	# but this does not seem to affect mkv containers made by ffmpeg?
	if (ending != "mkv") {
	    offset=2
	}
    }
    frm=1
    pkt_pts_time=pkt_pts_time-startpts
    #      <seek data="381841724" frame="9570" type="9"/>
    #      <seek data="159660" frame="9570" type="33"/>
    print "<seek type=\"9\"  data=\"" pkt_pos "\" frame=\"" frame "\"/>"
    print "<seek type=\"33\" data=\"" pkt_pts_time "\" frame=\"" frame "\"/>"
}