E-book Format Conversion

Calibre should do the job in most cases.
There was once I wanted to convert DjVu to PDF, but Calibre didn't work. And I used this method.

ffmpeg

This is always the first friend that comes to my mind when I need to do anything about files with audio and video.

Downmix multi-channel DTS-WAV audio to stereo FLAC.
```
ffmpeg -i input.wav -ac 2 output.flac 
```

Concat video chunks downloaded from sources that use HLS.

ffmpeg -i playlist.m3u8 -codec copy output.mkv
ffmpeg -allowed_extensions ALL -i playlist.m3u8 -codec copy output.mkv

Convert WEBM to MP3.
```
ffmpeg -i input.webm -codec:a libmp3lame -q:a 0 output.mp3
```
Reference: https://trac.ffmpeg.org/wiki/Encode/MP3
Merge audio and video.
```
ffmpeg -i video.mp4 -i audio.wav -c copy output.mkv
```
- Tip: When you're not sure what format to output to for audio-visual works, use mkv, since it can contain streams encoded by almost all codecs.
Cut audio.
```
ffmpeg -ss <start_position> -i <input> -to <duration> -c copy <output>
```
- where <start_position> and <duration> are in the form of hh:mm:ss.
Extract audio from video.
```
ffmpeg -i <input> -vn <output>
```
- -vn means no video.

shntool hash <file> Computes the MD5 or SHA1 fingerprint of PCM WAVE data. (from man page)

(more natural) upconv_7_photo > upconv_7_anime_style_art_rgb > cunet (less natural)
Higher denoise level, less natural.

Record your favorite radio programs.

rtmpdump -r rtmp://fms-base2.mitene.ad.jp/agqr/aandg333 -v -o output.flv

convert <image1> <image2> +append <result>