ffmpeg

ffmpeg

Command

Filter

List available filters
```
  ffmpeg -filters
```

Option

audio bit rate [Kbps]
```
  -ab 128
```
- 低いサンプルレートの場合、大きい値は設定できない、
  - 32khz未満の場合は160kbps以上の値は設定不可。
audio sampling rate [hz]
```
  -ar 16000
```
the number of channels
```
  -ac 2
```
- 1: monoral
- 2: stereo
sampling bit (audio codec)
```
  -acodec pcm_s24le
  -acodec pcm_16le
  -acodec pcm_u8
```
- 24 bit: -acodec pcm_s24le
- 16 bit: -acodec pcm_16le
  - signed int little endian
- 8 bit: -acodec pcm_u8
  - unsigned int
- list acodec
```
  ffmpeg -codecs
```

Example

Change sound to stereo 96 khz and 24 bit wav
```
  ffmpeg -i before.mp3 -ar 96000 -ac 2 -acodec pcm_s24le after.wav
```
- 音の高さを変えずにスピード変更

Reduce speed

  ffmpeg -i ./input.mp3 -filter:a "atempo:0.5" -vn ./output.mp3

音の高さを変えずにスピード変更

Increase speed

  ffmpeg -i ./input.mp3 -filter:a "atempo:2.0" -vn ./output.mp3

Higher pitch (assuming your audio is 44.1KHz)

  ffmpeg -i ./input.mp3 -filter:a "asetrate=r=48K" -vn ./output.mp3

Lower pitch (assuming your audio is 44.1KHz)

  ffmpeg -i ./input.mp3 -filter:a "asetrate=r=36K" -vn ./output.mp3

参考