What codec it is
audio, codec, file, ios
Solution
I would suspect it is a speech codec. For example RFC6716 and OPUS. The bit rate for this codec is 8-12 kbit/s for NB speech. The `0x0c` fits the `SILK` configuration for 20ms frame size.
| 0...3 | SILK-only | NB | 10, 20, 40, 60 ms |
The 20ms frame size gives around 14bytes. I tried to save the sample as 29-aud-bin.opus and open it in Firefox, but it lacks that header that other opus files have. A version of the `SILK` codec is also used by Skype.
Problem
I have a compressed file its size is 728 and somehow I know this is an audio file and it lasts 1040 ms The compressed file structure is straight forward: It is formed with 14 bytes blocks, each block starts with 0x0C: 0c xx xx xx xx xx xx xx xx xx xx xx xx xx 0c xx xx xx xx xx xx xx xx xx xx xx xx xx 0c xx xx xx xx xx xx xx xx xx xx xx xx xx 0c xx xx xx xx xx xx xx xx xx xx xx xx xx 0c xx xx xx xx xx xx xx xx xx xx xx xx xx 0c xx xx xx xx xx xx xx xx xx xx xx xx xx 0c xx xx xx xx xx xx xx xx xx xx xx xx xx 0c xx xx xx xx xx xx xx xx xx xx xx xx xx (xx) could be any hex number You can download compressed binary file here: http://dusijun.files.wordpress.com/2013/02/29-aud-bin.doc (please rename to *.aud ) Or text view in doc format http://dusijun.files.wordpress.com/2013/02/29-aud.doc There is no header nor meta information. The number of blocks depends on how long the actual audio is. Audio duration to file size is around 1.42 eg If file size = 9506 then audio could last for 9506*1.42 = 13580 ms around 13 S Anyone know what codec it could be? PS: The binary file is WeChat (ios) audio file. REF 1)How can I extract/play .aud files? http://www.boards.ie/vbulletin/showthread.php?t=2055891600 2) WeChat ios https://itunes.apple.com/us/app/wechat/id414478124?mt=8