Avidemux lets you align separate audio and video files so they run in sync.
Avidemux is an open-source video and audio editor that allows you to sync together audio and video content. The advantage of this function is that you don’t need to rely on the sound-recording element of your video camera. You can record audio with a dedicated microphone and concentrate the camera on the visual. This way, you get the best quality audio and the best quality visual at the same time. Avidemux offers a convenient and intuitive interface for lining up two media files so they run in tandem.
1. Click “File” and select an audio file from the browser. This will load into the Avidemux interface.
2. Select a format type. Both MP4 and Wave Audio, listed as “Wav,” are compatible with Avidemux. If you intend to load the finished media to a video-sharing site such as YouTube, select MP4. This is a lower quality format than Wave Audio, but it is smaller and therefore easier to upload. If you are not concerned with file size, select “Wav” as this is a lossless, uncompressed file type of higher quality.
3. Click “File” again and load the visual media file. This will load into a dedicated screen in the interface.
4. Hit play and let the video and audio roll at the same time. It’s probable that the video and audio will be out of sync, even if by only a second.
5. Click “Audio” and change the “Main Audio Source” option from “Video” to external audio. This configures Avidemux to play back only the audio on the imported track, rather than the sound picked up by the video camera.
6. Set the A and B locations. These cut off any unwanted media; for example, screen tests or those few seconds between turning on the camera or microphone and beginning the recording. By setting these points, you don’t waste processing power and time editing audio that you won’t use.
7. Adjust the number in the “Frame” box to line up the video with the audio. If the audio is happening after the corresponding action on screen (for example if a person’s mouth begins to move before you hear them speak) increase the number. If the audio is before the visual, decrease the number. Avidemux is a relatively basic program and there is no visual way of lining up the audio and video. This process is trial and error.
8. Click “Audio” and select “Gain.” This governs the overall volume of the audio. Select “Manual” and edit the figure in the box. If you set the gain too high, distortion will occur. Aim for the highest possible level before distortion so the volume is loud. If you hear crackling or buzzing, reduce the decibel figure in the box by single unit increments until it is gone.
9. Click “File” and select “Save.”