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Merged
LayNoah merged 1 commit into from
Jul 27, 2026
Merged

add resize gif file #52

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31 changes: 30 additions & 1 deletion doc/8_recording.md
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Original file line number Diff line number Diff line change
Expand Up @@ -78,7 +78,36 @@ speed=2
static_ffmpeg -i ${record_dir}/${record_name}.gif -filter:v "setpts=PTS/$speed,split[a][b];[a]palettegen[p];[b][p]paletteuse" ${record_dir}/${record_name}_${speed}.gif
```

## 4-2. extract frames
## 4-2. Reduce width / height (resize)

Shrink the output resolution. `scale=W:H` sets the target size; using `-1` for one side keeps the aspect ratio (and `-2` forces an even number, required by mp4/`yuv420p`).

### mp4 (by target width)

Set `width` and let the height follow the aspect ratio.

```bash
width=640
static_ffmpeg -i ${record_dir}/${record_name}.mp4 -vf "scale=${width}:-2" -pix_fmt yuv420p ${record_dir}/${record_name}_${width}w.mp4
```

### mp4 (by ratio)

`ratio < 1` shrinks (e.g. `0.5` = half size). `-2` keeps both sides even.

```bash
ratio=0.5
static_ffmpeg -i ${record_dir}/${record_name}.mp4 -vf "scale=trunc(iw*${ratio}/2)*2:trunc(ih*${ratio}/2)*2" -pix_fmt yuv420p ${record_dir}/${record_name}_${ratio}x.mp4
```

### gif (by target width)

```bash
width=480
static_ffmpeg -i ${record_dir}/${record_name}.gif -vf "fps=15,scale=${width}:-1:flags=lanczos,split[a][b];[a]palettegen[p];[b][p]paletteuse" ${record_dir}/${record_name}_${width}w.gif
```

## 4-3. extract frames

Frames are written to `frames/%07d.png` (7-digit index) in the current directory.

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