My problem was this, how to display two different video and audio sources (Freebox Revolution and XBOX) on two different media (TV and VIDEO PROJECTOR) keeping my AMP.
In fact this amp is a bit old and does not have HDMI inputs let alone HMDI outputs.
One solution would be to buy an amp with 2 HDMI outputs but it costs nearly 1,000 !!!
For less than 70 I found my happiness. Indeed, VIDEO PROJECTOR is connected to this switch with a 10m cable, and other devices with cables 1.5m. The switch sends the sound to my amp thanks to its optical output. It works well, the sound is very good and the image is transmitted quality. No loss recognized on the contrary I have a better sound thanks to the optical output! It is even possible to cross the sources and media. This means that it is possible to visualize the Freebox on TV while playing the XBOX on the VIDEO PROJECTOR.
So I recommend to everyone, even those who know not much (my case) !!! Done branching galleys and disconnect HDMI cable to view a particular source of such support.