Was this file recorded in Wowza? Are you using the LiveStreamRecord Addon or API, or are you using StreamType "live-record" to record?
If you are using LiveStreamRecord, try setting the startOnKeyFrame flag to true.
If you are using StreamType "live-record", try setting this Property in the /conf/[app-name]/Application.xml /Properties list:
The thought is that there is a section of audio at the start without video. One of the above methods should prevent that from happening.