Poor sound quality from a video clip in iMovie

I don't know the audio formats used by the numerous cameras and applications out there. Many, if not most, applications have options to select the audio format. Different cameras may record in varying audio formats, so their specs would need to be checked.

iMovie supported audio formats include mp3, WAV, AIFF, AAC, m4A. All of them should play fine. AIFF is the least lossy. It is just the Mp4 bucket that should have the AAC format. The .mov format is a bucket that can contain a variety of codecs, inclucing audio as well. As mentioned, not all Mp4 formats work with iMovie. It needs to be Mp4/AAC. AAC stands for Advanced Audio Coding. If you receive a file that is other than AAC for the Mp4 bucket, you can always convert it to

AAC with the free download, Handbrake.

Current iMovie supports video import formats Mp4/AAC, .mov, DV, HDV, Mpeg-4, M4v, H.264, HEVC (High Sierra and after, iMovie 10.1.8 and after). There might be others. A clip in one of the above formats should import into iMovie and play fine. There are no format settings for import -- it just automatically imports at the setting of the clip.

iMovie exports everything in Mp4 except when you select to export in Best Quality (pro res), in which case the export will be in .mov format with a high bitrate and file size. The audio codec used there is LCPM. iMovie will edit in the new HEVC H.265 format, but will convert to Mp4 on export.

-- Rich

The audio might be poor quality because it is in a format that iMovie doesn't like. Sometimes Mp3 audios cause problems, as well as some audio in Mp4 movies that don't use the AAC codec that iMovie supports.

You can try selecting your video clip in iMovie and doing a Modify/Detach Audio. (First duplicate your project to preserve your original version.) Then copy the detached clip into a newly created project, and share out the project as an Audio Only file. (Audio Only is an option in the share out settings box that appears when you share out a movie.) After selecting Audio Only you will see a little selection triangle that, when you click on it, will show a drop down menu with several audio codec options. Select AAC, and then share out. After sharing out, drag the shared out clip into your original project and place it below the video clip from which you initially detached the audio. See if it plays with good quality.

-- Rich