video-concat

Concat videos using ffmpeg. Videos can be any size or format.

Instructions

Create directories

Create two new directories in the repo's root directory: originals and reencoded.

Collect videos

Collect videos, which can be of any size or format. Put them in the originals directory. They should have unique names, regardless of extension.

Convert videos to have matching parameters

Run convert_videos.sh. This produces a new video for each video in the originals directory. All of the new videos will be written to reencoded, and will have the same codecs, format (mp4), dimensions (1280x720), and aspect ratio (will be padded with black if necessary).

If a video already exists in reencoded, the script will do nothing. This means that you can add new videos to originals and rerun the script without reconverting all videos.

Depending on your operating system, you may need to edit the ffmpeg args in the script, especially acodec and vcodec. Use google - there's lots of ffmpeg info online.

Produce list of video filenames

Run write_files_txt.sh. This produces a new file (filenames.txt), with one entry per video in reencoded, and an empty.mp4 entry between each one.

The empty.mp4 video is a two second, black video, which has matching parameters to the reencoded videos.

Order videos as desired

Rearrange entries in filenames.txt, if desired. The order of entries will be the order of videos in the final output.

Concatenate videos

Run concat_videos.sh, which will produce an output.mp4 from the videos in filenames.txt.

Occasionally scaling/SAR issues will pop up. To fix:

First figure out which video is the culprit (might need to trim down filenames.txt and repeatedly run concat_videos.sh until you've narrowed it down to one video).
Run the following command: ffmpeg -i originals/{NAME}.{EXTENSION} -vf scale=1280x720,setsar=1:1 originals/{NAME}1.mp4
Look at the output video. The aspect ratio may be off. Try rerunning the command with different scale values until the output looks right.
Replace the problematic video with the new one, and clear the reencoded video so we can reencode the new version: rm originals/{NAME}.{EXTENSION} && mv originals/{NAME}1.mp4 originals/{NAME}.mp4
Clear the old reencoded video and reencode the new version: rm reencoded/{NAME}.mp4 && convert_videos.sh
Now try to concat the videos again! There may be more than one problematic video so this process may need to happen multiple times. All of this could probably be automated, but that's a feature for the future.

System

Using ffmpeg version 3.4.6-0ubuntu0.18.04.1

Suggested use

Collect celebratory videos from friends and family for some special person's birthday or accomplishment. Concatenate the videos, and give the special person the result. If you're lucky, you may alleviate a modicum of our collective COVID isolatoin.

brockmuellers/video-concat