Opus codec for 0 A.D. sound files

[Salesome]

I did some research and found out that the Opus (Wikipedia) codec might be worth a try for the game's sound files.

Currently, all 0 A.D. music files are encoded with 160 kbit/s using OGG Vorbis. With Opus, it would be possible to encode them with 96 kbit/s, where the threshold for transparency is for this format (Source). Maybe they could even be encoded with 64 kbit/s (At least, I don't hear the difference). Several ambient sounds might be encoded with even lower bit rates (for speech, 32 kbit/s is sufficient using Opus (see link above)).

The sound files currently make up about 150 MB of the installer. The savings could amount to about 50-60 % by encoding with Opus at a lower bitrate, which would result in a ~75 MB smaller download. Doing a quick re-encode of all music files with 96 kbit/s VBR, I obtained 51 MB (as opposed to originally 109 MB).

One big advantage of the Opus format, apart from the better encoding quality, is a very low latency (~25 ms). It can also be packed into OGG containers (so the configuration files don't need to be re-written). A possible downside is that decoding Opus files takes more CPU power than OGG Vorbis (I am not a programmer though, so I cannot quantify that).

I attached a few 0 A.D. music files in Opus format as samples (encoded from the .wav files in trac).

Ammon-Ra_96_kbits.opus

Honor_Bound_2014_96kbits.opus

Ammon-Ra 64 kbits.opus

Honor_Bound_2014 64 kbits.opus

Edit: VLC Player can open the files.

Edited August 14, 2016 by Salesome

[niektb]

What kind of music player can I play your attached files with?

[Aghilas]

On 14/08/2016 at 5:46 PM, niektb said:

What kind of music player can I play your attached files with?

Salesome said: Edit: VLC Player can open the files.