Your WebM or OGV video may have negative or invalid timestamps. Some software produces video that starts at a time slightly less than zero, particularly if the audio and video frames are not aligned to start at the same time. (That is, the video may start slightly before 0 and the audio may start at 0.)
If the video is produced with ffmpeg
, try using the option -avoid_negative_ts 1
.
If you have the mkvtoolnix package installed you can view the timestamps in a webm file with the command mkvinfo -s
file.webm.