In an effort to get the sound replacement project restarted again I've implemented a way to read custom sound replacements in OpenTTD. It works similarly to the graphics replacements; the format of the files stays the same and OpenTTD just loads differently named files. It also hooks in directly to the content downloading system.
As proof of concept I've created a "NoSound" replacement set, which contains no sounds and can be downloaded from the content system in recent (>r17140) OpenTTD nightlies. As a result it will go into 0.8.0. Just place it in OpenTTD's data/ directory.
I've also created a tool to encode (and decode!) the new cat files; the format is slightly different than the old format, but that is so OpenTTD can still use the same hacks to load the original files. This tool can be downloaded at
http://www.openttd.org/download-catcodec
Please read docs/obs_format.txt for the format of the required, for OpenTTD to detect the sound set, .obs file.
Finally I have created, with the help of the #openttdcoop guys, a repository/tracker for the sound replacement pack. It's called OpenSFX and can be found at
http://dev.openttdcoop.org/projects/opensfx. I already added all samples from
http://wiki.openttd.org/Sound_Effects_Replacement that had a proper license and sounded decent. I also created a ticket/issue for each of the missing samples and hope that you can help finding/creating a suitable sample for the pack. Please check your local repositories whether I've forgotten any of the already existing samples.
I suggest that we use the Creative Commons Sampling+ 1.0 License as all existing samples are released under that license, which makes it the easiest for all.
Please mention the author of the samples you took and (re)mixed, so we can properly credit them too.
In the coming days I'll talk with the #openttdcoop guys about creating nightlies and making a first release available (via the OpenSFX site and the content download system).
Nightlies can be found at:
http://mz.openttdcoop.org/bundles/opensfx/nightlies/
Releases can be found at:
http://mz.openttdcoop.org/bundles/opensfx/releases/ and the online content system