Hello,
I’ve got some problems myself with wp-offload-media and WPML even though they say it is compatible.
I had a discussion with their developers, pointed some issues, and they managed to fix some bugs not long ago about this.
But here is what I know :
If you decide to not translate medias (and to not duplicate them when your insert a post), the media won’t be available in the translated language so first thing is you MUST duplicate medias to other language so they can be available in the translated language.
Then, if everything is fine, a “duplicate” will be created in the database. There won’t be 2 physical files but 2 attachment posts linking to the same file and, in the metadata of the duplicated attachment, there will be the ID of the original language attachement.
With this this meta information, wp-offload-media is able to recover the main language attachment and get its URL.
The very bad point about that is : If you have, let’s say, 5 languages on your site, wp-offload-media will count 5 activations down on your licence for each attachment, even though there is only one physical file moved to S3… I complained a little about that but they consider that is normal. So my very expensive license has already reached the limit because of this.
I’ve tried “Media cloud” and it is really an amazing plugin. Sadly, there is absolutely no WPML integration. I’ve actually started looking for writing it myself.
Some simple filters would do. I think it could fit in about 30-40 lines of code.
To the developer, don’t hesitate to contact me if I can help you build this integration or provide you with a WPML activation key ! That would be really awesome to make Media Cloud fully compatible with WPML.