I have an MP4 video file where the sound is out of sync and shorter than the video. I'm guessing it was recorded at 44.1k and then imported into the video as if it was 48k.

What's the easiest method of lengthening the audio? If I can extract the audio to WAV or something I could work on that but it seems to me I need to extract a 48k file not a 44.1k file.

Many thanks