How to fix FLV files: Build VBR Time Map with AviDemux

Avidemux is a freeware video editor for Linux, Mac OS and Windows

To fix FLV files with AviDemux:

1. Run AviDemux and open FLV file with it
2. Select "Audio" -> "Build VBR Time Map"
3. Change the Format (container) to MP4 if needed
4. Save the video under a new name (If you save it under the same name your original video will be lost!!!)