To resolve this issue, try VLC media player.

MP4 is a container that contains various kinds of data, so when there is a problem opening the file, it usually means that data in the container (an audio or video codec) is not compatible with the device’s OS. On some devices, particularly mobile, opening this file type can be problematic. On Windows, it opens in Windows Media Player. There is no need for third-party software. Simply double-clicking the file opens it. Its a browser-based tool so you dont need to download any software. MP4 files open in the operating system's default video player. VEEDs SWF to MP4 Converter is completely free to use. Many consider MP4 to be one of the best video formats available today. It is also a popular video format for streaming over the Internet, such as on YouTube. We cannot confirm if there is a free download of this software available. It is compatible with a wide range of devices and operating systems, using a codec to compress file size, resulting in a file that is easy to manage and store. Download of SWF Convert 1.2.3 was on the developers website when we last checked. It supports 8372 different conversion combinations of audio, video, image, document, archive, presentation, e-book and font file types. This online converter also offers other reliable tools to split, encrypt and decrypt files. MPEG-4 (MP4) is a container video format that can store multimedia data, usually audio and video. FreeFileConvert is an online tool to convert SWF to MP4 free.

Free swf converter for windows