Search in Baidu and download a powerful "format factory". It can convert almost all video formats into all video formats. There are also audio and images, which can be turned at will. As for the video file is too big, you can easily slim down. For example, a 1gb video file can be automatically compressed to 300 megabytes by converting it to 3gp ... If it is still too big, it can be cut to the length and size you want. You try!