64 lines
2.7 KiB
Markdown
64 lines
2.7 KiB
Markdown
---
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title: Lossless screen recording
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subtitle: Never waste resources with OBS again
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author: Amolith
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description: Recording your screen (or monitors) with ffmpeg for a high-quality lossless video that uses very few system resources
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date: 2018-08-12T17:15:20-04:00
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cover: /assets/pngs/ffmpeg-lossless.png
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categories:
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- Technology
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tags:
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- FFmpeg
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- CLI
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- Minimalism
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---
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I've been trying off and on for the past few weeks to figure out how to
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record my 1920x1080 monitor. The recording is going to be some music
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videos for a friend. Originally, it was just going to be a single
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background image for the whole video then I had the idea of using
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[cava](https://github.com/karlstav/cava) in a transparent terminal on
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top of the background. This didn't work at all because it actually kept
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freezing when I tried to record it. So I tried switching to
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[ncmpcpp's visualiser.](http://ncmpcpp.rybczak.net/) This still had
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horrible lag so I've been puzzling over how to use ffmpeg to
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*losslessly* record my second monitor. The reason OBS and similar screen
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recorders are so slow is because, most of the time, they encode to the
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end format while recording and that uses a lot of system resources. I
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finally figured it out and have pasted the command below.
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``` bash
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ffmpeg -video_size 1920x1080 -framerate 30 -f x11grab -draw_mouse 0 -i :0.0+1366,0 -c:v libx264 -crf 0 -preset ultrafast output.mkv
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```
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Above is exactly what I used for my 1080p monitor with 768p laptop
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screen. I've modified the command so you can see what you need to edit
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for your use-case.
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``` bash
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ffmpeg -video_size <target-resolution> -framerate 30 -f x11grab -i :0.0+<width-of-unused-monitor>,0 -c:v libx264 -crf 0 -preset ultrafast <filename>.mkv
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```
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If you do *not* want the cursor recorded, add `-draw_mouse 0` directly
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after `x11grab` like I did in the first command.
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My video was 470mb for a ~13 minute video. If you're going to archive
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the recording or are concerned about file size, re-encode it with a
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slower preset. This will be a lot slower and take a lot of CPU but the
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resulting file is *significantly* smaller than the original and still
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lossless. I this as a general purpose screen recorder. Previously, I was
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using OBS and the lag in the video was incredible but with ffmpeg, it's
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smooth as butter. The command for re-encoding is below:
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``` bash
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ffmpeg -i output.mkv -c:v libx264 -crf 0 -preset veryslow output-smaller.mkv
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```
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## Note
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This command only works with X, not Wayland. Skimming `ffmpeg`'s man
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page, I see that `video4linux2` is another option for capturing video so
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you may be able to replace `x11grab` with it for the same result. I have
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not tested this so I don't know if it'll work or not.
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