Error when importing video for frames extraction.
When importing a video for frames extraction. The extraction is not completed or only one image is extracted.
Video can be coded with many different codecs, not all are compatible. For example XVID codec which is not compatible.
There are many formats to code a video and not all of them can be implemented since some of them do not have the libraries needed to make the extraction.
Convert the video to mp4 format with H.264 codec (this format seems stable and well tested with Pix4Dmapper).
There are different software available on the Internet, many are free.
For example, Handbrake: https://handbrake.fr