Joining and Appending Video Clips in Avidemux

Avidemux can glue several files together with File > Append. The feature is quick when the clips share the same format, and this guide explains what "the same" means in practice, plus what to do when the clips differ.

Requirements for a clean append

Every clip must match the first one in these properties:

• Resolution and aspect ratio (for example all 1920x1080)
• Frame rate (all 25 fps, or all 29.97 fps)
• Video codec and profile (all H.264 High, for example)
• Audio codec, sample rate and channel count

Camera clips from the same device almost always match. Files from different sources usually do not, and appending them in Copy mode produces playback glitches or a file that refuses to open.

Step by step

1. Open the first clip with File > Open.
2. Choose File > Append and pick the second clip. Repeat for each additional file in order.
3. Scrub through the timeline to confirm the joins look right.
4. Set Video and Audio Output to Copy, pick the matching muxer and save.

When clips do not match

Convert every clip to a common format first. Open each one, set the same video encoder and settings (for example x264, CRF 20, 1920x1080, 25 fps through the Resize and Change FPS filters) and the same audio encoder, then save. After that, the converted files append without problems.

Numbered sequences such as clip_001.mp4, clip_002.mp4 can also be opened in one go: pick the first file and confirm when Avidemux asks whether to load the rest of the sequence.

Checking the result

Play across each join point in the preview. A frozen picture or a short audio dropout at a join means the parameters differed. Re-encoding the output with a video codec usually resolves it, since the encoder rebuilds the stream from decoded frames.