Base64 Video

I am pulling down a base64 string, which is then used in a HTML 5 video tag:

 <video controls="controls">
                <source type="video/mp4" [src]="sanitizer.bypassSecurityTrustResourceUrl(step.attachment)">

This works perfectly on iOS, and the video plays without any issue. However, on Android, the video does not play, I just get a blank video player.

Is there any way of playing the video on Android and iOS - I’m wondering if I need to convert the base64 string into an .mp4 file, if so, how? I do not want to store any video locally on the device if possible.