In this video, we learn how to fix MP4 audio issues in Sony Vegas Movie Studio. First, close the program from your computer. After this go to the website: http://tinyurl.com/mp4fix. Download this file and then go to the folder that the program is in and copy the name of it. From here, open the folder where the file is stored within Sony Movie Studio. Then, rename the file "qt7plug.old". Then, insert this into the previous folder and launch the program. This should solve you problem and you should be able to hear and use the MP4 audio that you want.