How to create GIFs and MP4 videos from NES emulator captures
Intro and some background (Jump over for the how to)
I recently started collaborating with a Brazilian website and podcast called Fliperama de Boteco. The name refers to a video arcade that happened to be in a low level type of bar (common on our late 80s and through the 90s) and the website is mainly focused on retro gaming.
I wanted to write an analysis on the game Vice: Project Doom for the NES and put some GIFs to illustrate parts of the gameplay, here is the result (in portuguese, but you can see the GIFs and videos).
Beforehand it sounded like an easy peasy tasks. It is 2018, GIFs are everywhere (as if it was the early 2000s), no big deal.
Well, It is easy, if you know where to look for, and you know some tips and tricks.
I did not record all my failed attempts, but I tested many software before reaching what I consider a working confortable solution.
See below how I did.
How to
Here is what you will need:
- The NES emulator FCEUX
- The Lagarith lossless video codec
- The FFmpeg software (In our tutorial, we’ll run it on Docker)
- Optionally, since we are going to use FFmpeg on the command line, I recommend to use ConsoleZ
Do your NES captures
Fire up the FCEUX emulator, load your ROM, play until the part you want to record.
Now simply go to the menu an select File > AVI/Wav > Record AVI..., select the path
where to save your file and when prompted for a codec select Lagarith Lossless Codec in the drop down.
Now play until you are finished (you can you the pause key to pause the recording), and select in the menu
File > AVI/Wav > Stop AVI.
That’s it, your capture is done.
Generate a GIF from a capture
Now, based on this nice blog post, I adapted the script convert_to_gif.bat
to run FFmpeg from Docker container (because I don’t like installing stuff):
SET palette=tmp/palette.png
SET filters=fps=50
ECHO "Generating palette"
docker run --rm -v %CD%:/data jrottenberg/ffmpeg -v warning -i /data/%1 -vf "%filters%,palettegen" -y /data/%palette%
ECHO "Generating gif"
docker run --rm -v %CD%:/data jrottenberg/ffmpeg -v warning -i /data/%1 -i /data/%palette% -lavfi "%filters% [x]; [x][1:v] paletteuse=diff_mode=rectangle" -y /data/%2
You can use it like: convert_to_gif.bat nes-capture.avi nes-capture.gif
One important remark, I set the output framerate to 50 FPS, even though I captured at 60fps.
The reason is that browsers are not very good at rendering GIFs with very small delay between
frames. After some tests I reached the conclusion 50 FPS was a good number as it was well
rendered in Edge and Chrome.
See the result below:
| 50 FPS - size: 47KB | 60 FPS - size: 53KB |
|---|---|
-Moves-50fps.gif) |
-Moves-60fps.gif) |
Generate a MP4 video from a capture
Again using Docker, I wrote this one line script convert_to_mp4.bat:
docker run --rm -v %CD%:/data jrottenberg/ffmpeg -i /data/%1 -map 0:0 -vf format=yuv420p -profile:v baseline -level 3.0 -preset veryslow -r 30 /data/%2`
Explaining the parameters a bit:
-map 0:0- Filters only track 0, which means only the video, no audio. Remove if you want audio-vf format=yuv420p- I don’t even know how to explain, but it does not work without it-profile:v baseline -level 3.0- See https://trac.ffmpeg.org/wiki/Encode/H.264#Compatibility-preset veryslow- Best compression, takes a bit more time, see https://trac.ffmpeg.org/wiki/Encode/H.264#Preset-r 30- Output at 30 FPS. It is sad, but certain devices still do not support HTML5 video at 60 FPS :(
You can use it like: convert_to_mp4.bat nes-capture.avi nes-capture.mp4
See the result below:
-profile:v baseline -level 3.0 -r 30 size: 187KB |
-profile:v high -level 4.2 unchanged framerate (~60FPS) size: 133KB |
|---|---|
Final Considerations
At the end I used both GIFs and videos in my blog post.
Both have their pros and cons.
GIFs can achieve a higher framerate (up to 50 FPS) in most devices and can produce smaller files depending on the type of action you have in the video.
Videos will produce smaller files if you have a lot of action going on, but you will have to lower the framerate if you want more compatibility with older devices.
My tip is to always test both and see which one fits best to your needs.