AirPlay mirroring on iPod touch 4G
You have an airplay icon, not an airplay mirroring icon on a 4th generation iPod. You need a 5th generation to get mirroring. On the iPad, there is an option for turning mirroring on and off. So on my iPod 4 I get sound but no video on my TV when using Netflix, for instance. On my ipad I get both sound and video.