Are you asking how you would use an MP4 and a WAV file in the same project?
I want to put a mp4 files in my video
I always get an error message
I have to transform my mp4 file into mp3 in prder to insert it in my video
Is it normal
All my music is from iTunes wich is MP4 format?
Apple doesn't like you using their iTunes music because it is copywrited, so they have protection schemes built in. You have to find some sort of third party conversion system that will defeat Apple and cheat the artists out of their rights.
Also, iTunes music is usually in the M4A format. Not MP4, right?
But Bill has definitely called it. iTunes music is loaded with copy protection. You can't use it as is any video project.
You can try converting it to a WAV using the free download Audacity and it should work.
Adding to Steve's suggestion, you can use Audacity like a recorder, not just a converter. You can record anything playing on your computer. You can use it to steal the soundtrack from anything and everything. For example, it is capable of making a copy of any YouTube soundtrack while you are playing it. I've not tried it, but I think you could steal the soundtrack off of any commercial DVD.
My understanding is that you can legally make a video for your personal use with any soundtrack you can find, including iTune music. But, as soon as you share it with anybody you are now legally violating the rights of the artist that created the soundtrack.
Rather than stretching the ethics and legality of copyrights, there are lots of excellent "music for videos" sites that give you permission to use the sound track anyway you want. Some are free, some cost money. All require you give a credit in your video.
I would be happy to post links to soundtrack sites if there is interest.
I would appreciate somme links