I use Wowza Streaming Cloud with Closed Captioning utilizing an RTMP encoder. At first, I had high difficulty in getting it to work reliably. I found that the best way to stream Closed Captioning to Wowza Streaming Cloud is to purchase an instance of the on-premise Wowza Streaming Engine. Convert the RTMP feed into HLS in the on-premise Wowza Streaming Engine. In the Wowza Streaming Cloud, select Wowza Streaming Engine as Encoder/Camera.
If you are using “OnTextData” CC with RTMP, any network jitter/packet-loss will garble your CC. Replace the UDP-based RTMP with TCP-based HLS and it will likely solve this issue.