経緯
Unityで360°動画を再生したい!
音声も3Dにしたい！
AudioSourceを周囲に配置しなきゃ!
音声をchannel毎に切り出さなきゃ…？
前提
ffmpeg version 3.2.2
やり方
ffmpeg -i in.mov -filter_complex 'channelsplit=channel_layout=5.1[FL][FR][FC][LFE][SL][SR]' -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]' front_center.wav -map '[LFE]' lfe.wav -map '[SL]' side_left.wav -map '[SR]' side_right.wav
filter_complexオプションのchannelsplitでチャンネルの切り分け方を指定する。
5.1ch以外のパターン
まずAudioの形式を調べる
$ ffmpeg -i in.mov
(省略)
Stream #0:0(eng): Audio: pcm_s24be (lpcm / 0x6D63706C), 48000 Hz, 4.0, s32 (24 bit), 4608 kb/s (default)
(省略)
48000 Hzの後の4.0で4.0chとわかる
4.0chのChannel LayoutはFL+FR+FC+BCなので、
ffmpeg -i in.mov -filter_complex 'channelsplit=channel_layout=4.0[FL][FR][FC][BC]' -map '[FL]' front_left.wav -map '[FR]' front_right.wav -map '[FC]' front_center.wav -map '[BC]' bc.wav
で切り出せる。
めでたしめでたし。
Channel-Layout
channel layoutいろいろあるのでまとめ
https://www.ffmpeg.org/ffmpeg-utils.html#Channel-Layout
channelのリスト
| id | channel |
|---|---|
| FL | front left |
| FR | front right |
| FC | front center |
| LFE | low frequency |
| BL | back left |
| BR | back right |
| FLC | front left-of-center |
| FRC | front right-of-center |
| BC | back center |
| SL | side left |
| SR | side right |
| TC | top center |
| TFL | top front left |
| TFC | top front center |
| TFR | top front right |
| TBL | top back left |
| TBC | top back center |
| TBR | top back right |
| DL | downmix left |
| DR | downmix right |
| WL | wide left |
| WR | wide right |
| SDL | surround direct left |
| SDR | surround direct right |
| LFE2 | low frequency 2 |
channel layout のリスト
| id | channel layout |
|---|---|
| mono | FC |
| stereo | FL+FR |
| 2.1 | FL+FR+LFE |
| 3.0 | FL+FR+FC |
| 3.0(back) | FL+FR+BC |
| 4.0 | FL+FR+FC+BC |
| quad | FL+FR+BL+BR |
| quad(side) | FL+FR+SL+SR |
| 3.1 | FL+FR+FC+LFE |
| 5.0 | FL+FR+FC+BL+BR |
| 5.0(side) | FL+FR+FC+SL+SR |
| 4.1 | FL+FR+FC+LFE+BC |
| 5.1 | FL+FR+FC+LFE+BL+BR |
| 5.1(side) | FL+FR+FC+LFE+SL+SR |
| 6.0 | FL+FR+FC+BC+SL+SR |
| 6.0(front) | FL+FR+FLC+FRC+SL+SR |
| hexagonal | FL+FR+FC+BL+BR+BC |
| 6.1 | FL+FR+FC+LFE+BC+SL+SR |
| 6.1 | FL+FR+FC+LFE+BL+BR+BC |
| 6.1(front) | FL+FR+LFE+FLC+FRC+SL+SR |
| 7.0 | FL+FR+FC+BL+BR+SL+SR |
| 7.0(front) | FL+FR+FC+FLC+FRC+SL+SR |
| 7.1 | FL+FR+FC+LFE+BL+BR+SL+SR |
| 7.1(wide) | FL+FR+FC+LFE+BL+BR+FLC+FRC |
| 7.1(wide-side) | FL+FR+FC+LFE+FLC+FRC+SL+SR |
| octagonal | FL+FR+FC+BL+BR+BC+SL+SR |
| downmix | DL+DR |
まとめ
FFmpegは奥が深いなぁ…
参考
channelsplit
https://ffmpeg.org/ffmpeg-filters.html#channelsplit
Channel Layout
https://ffmpeg.org/ffmpeg-utils.html#Channel-Layout