What you’ll need, is the Wowza Transcoder Add-On (which now comes for free with the Wowza Server Pro Edition license), and multiple powerful servers that can convert 16HD SDI channels into video streams. Please have a look at https://www.wowza.com/docs/wowza-transcoder for more information about the Transcoder Add On. You may also be interested in some benchmarks, to compare your situation with test results from various configurations; see https://www.wowza.com/docs/wowza-transcoder-performance-benchmark