This problem occurs with the Sky HDTV Decoder Plus SHR23 and the Splitter HDMI de 1 entrada para 4 HUIYISHUN outputs, but possibly also affects other decoders and other splitters. I just noticed the problem after installing SHR23, but it is possible that already happened before and I haven't noticed.
My setup is as follows: the HDMI output of the decoder is connected to the input of the Sky Splitter HDMI. The first output of the Splitter HDMI is connected to the Receiver Yamaha RX-A830, and the second output of the Splitter HDMI is connected to the HDMI Extender Set, It takes the image and sound of the Sky to another more distant TV (Slave Point).
The problem is that with this configuration, the Sky was getting audio in Receiver just as PCM 2.0, even when Dolby Digital was linked in Sky decoder. I realized that calling the Sky directly in the receiver this problem does not occur and he can play Dolby 5.1 and Dolby 2.0 correctly in the channels that offer audio with this encoding. The problem was not leaving only the receiver connected to the splitter.
The solution I found was quite simple, just inverted the outputs of the Splitter HDMI, passing the first HDMI Extender Set and the second in Receiver Yamaha RX-A830. Thus the audio Dolby 5.1 or Dolby 2.0 arrived correctly in receiver. Apparently the second door takes precedence in time to negotiate audio supported, ou something.
As for the slave point, He does not have a receiver. I figured that the TV could be muted because of not being able to decode the Dolby 5.1, but that didn't happen. I don't know if it is decoding the Dolby 5.1 or if the PCM audio is also being broadcast in parallel with Dolby, so that the receiver uses the Dolby and the slave point TV uses the PCM.