Creating the movie of your life

My open source, minimalist video diary app just got a huge update. See the changelog for more info.

I would like to share some technical details about this update:

1. FFmpeg is the real deal

The videos recorded with the previous version of the app had a different configuration than the ones recorded with the new version. Also, the new feature to add videos from the gallery could bring any kind of video, so I needed to make sure that all videos would have the same configuration. That’s because I wanted to be able to concatenate them with the concat method, which is by far the fastest way to do it without losing quality. All this was only possible with the help of ffmpeg-kit.

Here are some related commands I used and might be useful if you are trying to do something similar:

# Add metadata to a video
ffmpeg -i input.mp4 -metadata artist="$artist" -metadata album="$album" -metadata comment="$comment" -c copy output.mp4

# Scale a video 1920x1080 and automatically add black bars to keep the aspect ratio
ffmpeg -i input.mp4 -vf scale=1920:1080:force_original_aspect_ratio=decrease,pad=1920:1080:(ow-iw)/2:(oh-ih)/2:black -c:a copy -c:s copy output.mp4

# Trim a video
ffmpeg -i input.mp4 -ss 00:00:00 -to 00:00:10 -c copy output.mp4

# Add subtitles to a video as default subtitles using a .srt file
ffmpeg -i input.mp4 -c:v copy -c:a copy -map 0:v -map 0:a? -map 1 -disposition:s:0 default output.mp4

# Change framerate to 30, audio codec to aac and video codec to h264
ffmpeg -i input.mp4 -r 30 -c:a aac -c:v h264 output.mp4

# Change audio stream to mono, 44100Hz, 256kbit/s
ffmpeg -i input.mp4 -ac 1 -ar 44100 -b:a 256k output.mp4

# Add an empty audio stream to a video that doesn't have one, matching the video's duration
ffmpeg -i input.mp4 -f lavfi -i anullsrc=channel_layout=mono:sample_rate=44100 -shortest -c:a aac -c:v copy output.mp4

# Concatenate multiple videos into one using a .txt file
ffmpeg -f concat -safe 0 -i input.txt -c copy output.mp4


  • c:a and c:v are the same as codec:a and codec:v.
  • c:{a/v/s} copy means that the codec will be copied from the input file to the output file.
  • The ? in -map 0:a? means that the command will ignore errors if the input video doesn’t have an audio track.
  • Add -y to the end of the command to overwrite the output file if it already exists.
  • If you want to concatenate videos with different frame rates, you can use -vsync vfr.

How did I learn all this? That brings us to the next point.

2. ChatGPT and GitHub Copilot

While FFmpeg is amazing, its documentation is kinda… disappointing. Even StackOverflow was not so helpful. So, I turned to ChatGPT and it magically brought most of those commands that achieved what I wanted. After copying them, GitHub Copilot would complete another good portion of the work, like error handling and UI changes. This duo is a very powerful combination and if you haven’t yet, I highly recommend you to try it out. I don’t think I can live without it anymore lol.

3. Fun Fact: Google rejected my first attempt to publish the update

In my first attempt to publish the update, Google rejected it because I was requesting the MANAGE_EXTERNAL_STORAGE permission, which is now a very restricted permission that few apps can make use of. This allowed me to save videos in the root path of the device and I didn’t have to care about the permission errors some devices were reportedly having in the previous version even when storage permission was granted. I was able to fix it by using the MediaStore API instead, thanks to the media_store_plus package. I had to change a lot of code to make it work, but at the end of the day, it was a good thing since I was able to implement more features along with the requested storage migration πŸ˜….

4. A huge thanks to everyone who supported me

I wouldn’t have been able to finish this update - at least not so quickly and stable like it was - if I hadn’t received that much help from the community and friends. So, thank you to everyone who supported me in any way: with code, testing, suggestions and donations. I am very, very grateful. This update is dedicated to you.

What’s next?

In the short term, bug fixes and minor improvements based on the feedback I get from users.

In the long term, I am planning to give the app a brand new UI and redo its architecure (currently, it’s a complete mess to be honest, but everything works 🀣). There’s no ETA since I am making a game right now, but this project is meaningful to me and I am definitely willing to work hard on it again in the future.