Hikvision DS-7208HUHI-F2/S - Is there sound on the HDMI output

I am trying to use the output from a Hikvision DVR to stream to the internet. I want to inject an audio stream into the HDMI output. If I try to do this after the ouput (using an audio embedder) I get a chipmunk result on the audio. I'm wondering if there is already an audio signal on the stream. Or alternatively can I inject it via the camera input ? I know I can feed audio into 4 of the channels for recording, in fact I do that on one of them, but what I need to know is if it is possible...

Hikvision DS-7208HUHI-F2/S - Is there sound on the HDMI output